That is exactly where art's criticality runs into the void.
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Take leaders who score low on nurturing and high on criticality.
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This would, in theory, prevent a criticality excursion and meltdown like Chernobyl's.
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With celebration and criticality, I pull references from lesbian legacies and failures.
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DC: Whatever happens next, Sarah's the one who recognized the criticality of it.
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I also hope to cultivate more social/political engagement and criticality in the fairs.
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The mission criticality of these types of services is only growing by the day.
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Can it, with a straight face, still claim to reflect a form of "radical" criticality?
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But despite its criticality, in a given market there is typically only one grid. Why?
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I have learned how to listen, and I have developed a criticality, and therefore intentionality.
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Especially in drone videos, because in YouTube, the criticality factor is way higher than any other segment.
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And although the internet is largely free of fingerprints, Ruff's work beckons us to maintain that same criticality.
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This is another way that this exhibition responds to Jessica Morgan's call to reappraise the criticality of Pop.
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Minerva Cuevas: DISIDENCIA gathers a body of work that criticizes institutions, revealing layers of criticality and globally minded research.
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New market entrants must carefully consider the mission criticality and depth of workflow and use cases that they subsume.
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We will continue to strive to be a beacon of hope, positivity, and criticality in the world of games and beyond.
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They frequently offer a wider perspective and greater criticality, and show contemporary issues under a different, more considered and nuanced light.
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The basic premise is that criticality is a tipping point between order and chaos, when these two extremes are tenuously in balance.
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We used real world technical examples to illustrate the criticality of the tools and techniques that the 2013 agreement appear to control.
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In her new book, You Have the Right to Remain Fat she does all that with refreshing criticality and resonant personal reflections.
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Ice is a more organized molecular structure, compared to water; criticality is the in-between of ice and water, when both exist together.
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This growth in SOF manpower and money is noteworthy, but it is SOF's growing criticality to U.S. national security that demands real attention.
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We recognize the criticality to pay attention to the weaker countries, those were health systems are not tuned to respond to that emergency.
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All of this comes with a dose of quixotic humor and '90s anti-corporate criticality—and a characteristically millennial lack of concern for credentials.
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We say that the largest number of configurations is achievable with criticality, and in this case it's achievable even more so during the LSD state.
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The network's electrical activity also displays a property unique to complex systems like the brain: "criticality," a state between order and chaos indicative of maximum efficiency.
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"We've seen that there's a difference between the psychedelic brain and the normal brain: The psychedelic brain seems to be tuned closer to criticality," she says.
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If anything, Kaiser does something unfashionable but very much needed in this era of bloated rhetoric and claims of meta-criticality: he comes across as sincere.
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As this type of slick, ahistorical, and acontextual show becomes ever more common, one wonders what kind of criticality could possibly overthrow their smooth denial of context.
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Our participatory democracy is at risk without raising the criticality of securing the election system, and failing to apply modern conveniences whose exclusion directly stifles voting turnout.
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This is the state that Chialvo and his fellow criticality-believers thought the brain was in: always on the verge of chaotic behavior, but never fully crossing over.
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Ms. Munroe sees the state of the Chinese art world as "hijacked by the art market" with very little nuance or criticality, resulting in less tolerance by Western art critics.
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Shortly after acquiring our space, we composed our Womanifesto, which states our objectives within our forum to foster criticality, promote progressive language, destroy expectations, cultivate cooperation, and surprise the senses.
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Numerous well known names in contemporary art are originally from Diyarbakır and surrounding Mardin, including Ahmet Ögüt and Halil Altındere, artists who have found success abroad without compromising their criticality.
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There is a place-based knowledge system and localized criticality that they bring to the table through their families and relationships that informs much of the work we have produced here.
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If nothing else, the debate and discussion around the proposed Space Force highlighted the criticality and importance of space to both the national security and economic security of the United States.
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The problem is that it's not a prestigious job, it's a critical job, and so the people who get prestige versus the people that get criticality are very different kinds of people.
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Even in Washington, there's various lobbying organizations coming together and a lot of them, we won't join because they have, as their members, some people who espouse the criticality of anonymous transactions.
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In her new book, You Have the Right to Remain Fat —coming out in print on The Feminist Press on August 14—she does all that with refreshing criticality and resonant personal reflections.
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The hope is that the director nominee sees the criticality of the OFRs data standards mission, preserves it and can transform the OFR from its economic analysis mission to its data science destiny.
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The curator said she was struck by Mr. Wong's "sharp, pungent, intelligent sense of criticality and humor" from the first time she encountered his work at Art Basel Miami Beach in December 2016.
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One is the criticality of 5G for the United States and the innovation cycle that's underway that we currently as a nation are behind on.... This is very important policy-wise for the country.
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Power-law behavior, he said, indicates that a complex system operates at a dynamical sweet spot between order and chaos, a state of "criticality" in which all parts are interacting and connected for maximum efficiency.
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We made these decisions by evaluating the criticality of each position, whether certain jobs could be done more efficiently and productively, and by assessing the specific skills and abilities of each individual in the company.
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At Fukushima, a tidal wave swamped the diesel backup generators needed to cool the reactor, resulting in a meltdown of sorts, though one that fortunately didn't get bad enough to turn into a full-blown criticality excursion.
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"We made these decisions by evaluating the criticality of each position, whether certain jobs could be done more efficiently and productively, and by assessing the specific skills and abilities of each individual in the company," Musk wrote.
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As a fellow culture worker, I'm saddened at the ways in which the race, gender, sexuality and other identity categories of artists often become politicized with a sweeping lack of criticality inside the space of the museum.
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However, the incentive to pay for IoT ransomware will not stem from irreversibility but rather from the timeliness of the attack and the criticality and potential losses of losing access to critical devices for any amount of time.
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This is refreshing, not because it implies that the artworks should stand on their own, but as a political signal against the convention of touting artists' diversity as a symbol of the institution's progressive politics or post-colonial criticality.
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The brain's reorganization was showing signatures of something called criticality, or a concept of brain activity that says that our brains dance on the fine line between order and total chaos, and that LSD was pushing us closer to the edge.
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Moreover, on a number of occasions in the past, Pakistan and the United States have agreed at the highest level on the criticality of border management and settlement of refugees as fundamental issues in achieving any degree of success in Afghanistan.
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Criticality, for the purpose of the DPA, should pertain only to those industries whose continued operation is not only directly necessary for the national defense, but for which there is no suitable alternative and which cannot be sustained through private-sector demand.
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Britain's Department of Health & Social Care has urged Malaysian authorities to prioritise the production and shipment of gloves that are of "utmost criticality for fighting COVID-19," showed a letter dated March 20 to glove maker Supermax Corp and shared with Reuters.
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Since its creation, some lessons that could be applied in a US context around profiling criteria for incoming volunteers, efforts toward shifting the threat narrative—although it's not a function of the unit—and the criticality behind effective leadership rose in prominence.
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"Our whistleblowing process is one of the most important means by which we protect our culture and values at Barclays and I certainly want to ensure that all colleagues, and others who may utilize it, understand the criticality which I attach to it, " he added.
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" In an email to employees, Musk said the decisions involving the "company-wide restructuring" were made "by evaluating the criticality of each position, whether certain jobs could be done more efficiently and productively, and by assessing the specific skills and abilities of each individual in the company.
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If we were able to take the brain closer to criticality, where we allow the musician to use the whole spectrum of musical notes, the whole repertoire, then it may really help with the brain dynamics not getting stuck, or getting freer out of this stuck pattern.
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"Both the OPEC and non-OPEC groups understand that both sides would have to keep to the deal otherwise it falters so I think the urgency of now and the criticality of the economy they have to protect is enough incentive for everybody to align this time," he added.
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Deservedly or not, Sanders sits at the iconic horseshoe-shaped desk once occupied by Brady (and many of his distinguished predecessors and successors), who is widely viewed as having set the gold standard for balancing the criticality of telling the truth with advancing the agenda of his boss.
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"We made these decisions by evaluating the criticality of each position, whether certain jobs could be done more efficiently and productively, and by assessing the specific skills and abilities of each individual in the company," Tesla CEO Elon Musk wrote to employees in an email obtained by TechCrunch.
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"They've been doing a great deal, but it just heightens the urgency of taking out Raqqa and Mosul and developing better intelligence, and it just heightens the criticality of us understanding what a terrible threat this really is," McCain told The Hill, referring to ISIS's stronghold cities. Sen.
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The sculpture, which was commissioned by local real estate empire Two Trees and is scheduled to be in Brooklyn Bridge Park through August, is an endearingly public iteration of Kass's career-long project to inject some real world criticality and humor into the macho and self-serious Modern art canon.
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In terms of Joron's own poetic practice, this musical tuning toward criticality —toward the emergence (and emergency) of ontological lament — plays out on the page through a formidable ensemble of techniques, including the use of densely patterned consonance and assonance, internal rhyming, strategic caesuras, the masterful modulation of vowel sounds, and entrancing homophonic orchestration.
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"We were friends online first, sharing our thoughts and feelings through the retweets and reposts of this vast body of knowledge not available anywhere else in our lives, at least not to that level of criticality, and from the range of perspectives that you find in certain communities on Tumblr and Twitter," says Parker of how the collective started.
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In "The Emergency," an important treatise from his ambitious collection of essays and prose poems The Cry at Zero (2007), Joron draws on concepts from complex systems theory to describe the process of lexical exponentialization: A poem tunes itself toward a state of criticality, a condition of language in which single words have the widest possible range of effects.
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Another of the more palatable works in the exhibition is American artist Cécile Evans's video installation, What the Heart Wants (2016), which offers a modicum of criticality set within an immersive environment that includes a room flooded with water and a catwalk leading up to a large screen projecting images of a fictional dystopic world, while a voiceover debates what it means to be human.
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One particularly harrowing paragraph lists off the consequences bluntly: "If the power grid infrastructure were to collapse, the United States would experience significant: Although the report does not dwell on the implications, it acknowledges that a national power grid failure would lead to a perfect storm requiring emergency military responses that might eventually weaken the ability of the US Army to continue functioning at all: "Relief efforts aggravated by seasonal climatological effects would potentially accelerate the criticality of the developing situation.
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In nuclear engineering, prompt criticality describes a nuclear fission event in which criticality (the threshold for an exponentially growing nuclear fission chain reaction) is achieved with prompt neutrons alone (neutrons that are released immediately in a fission reaction) and does not rely on delayed neutrons (neutrons released in the subsequent decay of fission fragments). As a result, prompt criticality causes a much more rapid growth in the rate of energy release than other forms of criticality. Nuclear weapons are based on prompt criticality, while most nuclear reactors rely on delayed neutrons to achieve criticality.
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Nuclear criticality safety is a field of nuclear engineering dedicated to the prevention of nuclear and radiation accidents resulting from an inadvertent, self-sustaining nuclear chain reaction. Nuclear criticality safety is concerned with mitigating the consequences of a nuclear criticality accident. A nuclear criticality accident occurs from operations that involve fissile material and results in a sudden and potentially lethal release of radiation. Nuclear criticality safety practitioners attempt to prevent nuclear criticality accidents by analyzing normal and credible abnormal conditions in fissile material operations and designing safe arrangements for the processing of fissile materials.
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Airplane in-flight information system has much lower criticality than flight control systems, yet both coexist in one "mixed criticality" machine. A mixed criticality system is a system containing computer hardware and software that can execute several applications of different criticality, such as safety- critical and non-safety critical, or of different Safety Integrity Level (SIL). Different criticality applications are engineered to different levels of assurance, with high criticality applications being the most costly to design and verify. These kinds of systems are typically embedded in a machine such as an aircraft whose safety must be ensured.
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LA-3611 A Review of Criticality Accidents, William R. Stratton, Los Alamos Scientific Laboratory, 1967LA-13638 A Review of Criticality Accidents (2000 Revision), Thomas P. McLaughlin, et al., Los Alamos National Laboratory, 2000.
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The criticality of an element is a measure of how much the element has affected the 'q value' (i.e. performance) of the group to which it belongs. Elements with a high criticality cause more 'down-time' or unavailability on average and are thus critical to the performance of the group. The criticality of an element may vary according to the level of the group (e.g.
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A continuous model of self-organised criticality is proposed by using tropical geometry.
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This criticality accident is estimated to have produced 4.4 x 1018 fissions, or about .
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The Criticality Index allows you to identify tasks that are likely to cause delays to the project. By monitoring tasks with a high Criticality Index a project is less likely to be late. If a task has a 100% Criticality Index it means that during the analysis no matter how the task durations varied, the critical path always included the task. The task is therefore likely to be key in completing the project on time.
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The Dehaene-Changeux Model contributed to the study of nonlinearity and self- organized criticality in particular as an explanatory model of the brain's emergent behaviors, including consciousness. Studying the brain's phase- locking and large-scale synchronization, Kitzbichler et al. (2011a) confirmed that criticality is a property of human brain functional network organization at all frequency intervals in the brain's physiological bandwidth.Kitzbichler MG, Smith ML, Christensen SR, Bullmore E. Broadband criticality of human brain network synchronization.
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Four scientists died, including Harry Daghlian and Louis Slotin in criticality accidents involving the demon core.
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The ship departed Ōminato on 26 August 1974, and the reactor attained criticality on 28 August.
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Once the criticality assessment is completed for each failure mode of each item, the FMECA matrix may be sorted by severity and qualitative probability level or quantitative criticality number. This enables the analysis to identify critical items and critical failure modes for which design mitigation is desired.
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Sachdev has made numerous contributions to quantum field theories of quantum criticality in insulators, superconductors, and metals.
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Material criticality is going to be an essential factor in the industrial production process for the foreseeable future.
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TEPCO claimed that there was a small but non-zero probability that the exposed fuel assemblies in the Unit 4 reactor could reach criticality. The BBC commented that criticality would never mean a nuclear explosion, but could cause a sustained release of radioactive materials. Criticality is usually considered highly unlikely, owing to the low enrichment level used in light water reactors.Wikibooks:Radioactive Waste Management/Spent Nuclear Fuel American nuclear engineer Arnold Gundersen, noting the much greater power and vertical debris ejection compared to the Unit 1 hydrogen blast, has theorized that the Unit 3 explosion involved a prompt criticality in the spent fuel pool material, triggered by the mechanical disruption of an initial, smaller hydrogen gas explosion in the building.
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Recently however this metaphor has been subject of quantitative formulation using complex systems concepts such as criticality, meaning that a healthy ecosystem is in some sort of balance between adaptability (randomness) and robustness (order) . Nevertheless the universality of criticality is still under examination and is known as the Criticality Hypothesis, which states that systems in a dynamic regime shifting between order and disorder, attain the highest level of computational capabilities and achieve an optimal trade- off between robustness and flexibility. Recent results in cell and evolutionary biology, neuroscience and computer science have great interest in the criticality hypothesis, emphasizing its role as a viable candidate general law in the realm of adaptive complex systems (see and references therein).
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Criticality index is mainly used in risk analysis. The Criticality Index of an activity (task) can be expressed as a ratio (between 0 and 1) but is more often expressed as a percentage. During a (e.g. Monte Carlo) simulation tasks can join or leave the critical path for any given iteration.
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Criticality is the normal operating condition of a nuclear reactor, in which nuclear fuel sustains a fission chain reaction. A reactor achieves criticality (and is said to be critical) when each fission releases a sufficient number of neutrons to sustain an ongoing series of nuclear reactions. The International Atomic Energy Agency defines the first criticality date as the date when the reactor is made critical for the first time. This is an important milestone in the construction and commissioning of a nuclear power plant.
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Discussion on the brain's criticality have been done since 1950, with the paper on the imitation game for a Turing test. In 1995, Herz and Hopfield noted that self- organized criticality (SOC) models for earthquakes were mathematically equivalent to networks of integrate-and-fire neurons, and speculated that perhaps SOC would occur in the brain. Simultaneously Stassinopoulos and Bak proposed a simple neural network model working at criticality which was expanded latter by Chialvo and Bak. In 2003, the hypothesis found experimental support by Beggs and Plenz.
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The centre houses a Fast Breeder Test Reactor (FBTR), which attained its first criticality in October 1985. A few years later, in 1994, SQUID, ASIC and Diamond Anvil Cells were developed. In the same year, High-Power Physics and Engineering Experiments were undertaken in the FBTR. In 1996, KAMINI reactor reached criticality.
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This spike can be easily detected by radiation dosimetry instrumentation and "criticality accident alarm system" detectors that are properly deployed.
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Operation is now expected by October 2020 and September 2021 respectively. Unit 3 achieved first criticality on 22 July 2020.
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During this step the assumptions are identified and there is a determination of criticality. The hardest part of CAP is to identify the assumptions that are not written down. To determine the criticality of the assumptions, they must be quantified. This makes it possible to put the financial results in a spreadsheet and link them.
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Material criticality is a relatively new field of research. As global industrial activity continues to increase a wide array of stakeholders are paying more attention to material criticality in order to assess how production processes may be impacted and made more efficient. British Petroleum, the United States Department of Energy, and the European Union have all established review procedures to determine material criticality and how it affects their behavior. Additionally, there has been a growing body of academic study in this field, led by Thomas Graedel of Yale.
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Wind River® Helix™ Virtualization Platform consolidates multi-OS and mixed-criticality applications onto a single edge compute software platform.
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A dollar symbol is used as unit of reactivity for a nuclear reactor, 1$ being the threshold of slow criticality, meaning a steady reaction rate, while 2$ is the threshold of prompt criticality, which means a nuclear excursion or explosion. The dollar sign was used as a letter in the Turkmen alphabet from 1993 to 1999.
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In neuroscience, the critical brain hypothesis states that certain biological neuronal networks work near phase transitions.Ludmila Brochini, Ariadne de Andrade Costa, Miguel Abadi, Antônio C. Roque, Jorge Stolfi, Osame Kinouchi. Phase transitions and self-organized criticality in networks of stochastic spiking neurons. Available at Hesse, J. & Gross, T. Self-organized criticality as a fundamental property of neural systems.
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Conversely tasks with a low or zero Criticality Index are much less likely to cause a delay in the project finish date.
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It was classified a serious criticality accident. The incident resulted in radiation exposure for 667 people and the death of two workers.
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Keeping the reactor in the zone of chain reactivity where delayed neutrons are necessary to achieve a critical mass state allows mechanical devices or human operators to control a chain reaction in "real time"; otherwise the time between achievement of criticality and nuclear meltdown as a result of an exponential power surge from the normal nuclear chain reaction, would be too short to allow for intervention. This last stage, where delayed neutrons are no longer required to maintain criticality, is known as the prompt critical point. There is a scale for describing criticality in numerical form, in which bare criticality is known as zero dollars and the prompt critical point is one dollar, and other points in the process interpolated in cents. In some reactors, the coolant also acts as a neutron moderator.
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Today — Initial Criticality. www.tva.com. Retrieved 23 May 2016. , a transformer fire had delayed the start of commercial operation past the late summer goal.
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This made achieving criticality impossible, requiring fuel replacement. The restart was scheduled for October 2008, having been moved back five months.World Nuclear News.
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These changes did not prevent another criticality accident from happening at Los Alamos the following year. Louis Slotin, a colleague of Daghlian's, was killed in 1946 while performing criticality tests on the same plutonium core. After these two incidents it became known as the "demon core", and all similar criticality experiments were halted until remote-controlled assembly devices were more fully developed and available. Daghlian was memorialized on May 20, 2000, by the city of New London, with the erection of a memorial stone and flagpole in Calkins Park, which was unveiled by his brother and sister.
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Basically, most errors are currently committed when making confusion between priority attribution and criticality management. As priority defines an order between different tasks or messages to be transmitted inside a system, criticality define classes of messages which can have different parameters depending on the current use case. For example, in case of car crash avoidance or obstacle anticipation, camera sensors can suddenly emit messages more often, and so create an overload in the system. That is when we need to make Mixed- Criticality operate : to select messages to absolutely guarantee on the system in these overload cases.
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A criticality accident is an uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, or divergent chain reaction. Any such event involves the unintended accumulation or arrangement of a critical mass of fissile material, for example enriched uranium or plutonium. Criticality accidents can release potentially fatal radiation doses, if they occur in an unprotected environment.
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For any finite thickness, this corresponds to an infinite mass. However, criticality is only achieved once the thickness of this slab exceeds a critical value.
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The Criticality Index expresses how often a particular task was on the Critical Path during the analysis. Tasks with a high Criticality Index are more likely to cause delay to the project as they are more likely to be on the Critical Path. If a task does not exist for some iterations (e.g. it is probabilistic) then it is marked as not being critical.
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For example, a task that existed for 50% of the iterations and was critical 50% of the time it existed would have a Criticality Index of 25%.
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If the occurrence is very sparse, this would be 1 and the RPN would decrease to 100. So, criticality analysis enables to focus on the highest risks.
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Austin voters authorized the Quentin Camp Foundation on November 3, 1981 to sell the city's 16 percent interest in the STP."General Municipal Election: November 3, 1981" City of Austin No buyers were found. Unit 1 reached initial criticality on March 8, 1988 and went into commercial operation on August 25. Unit 2 reached initial criticality on March 12, 1989 and went into commercial operation on June 19.
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These financial impacts change for various assumptions. CAP measures the criticality of an assumption as a change in the net present value of a venture (NPV). To determine criticality each assumption is assigned a range of uncertainty: base case, best and worst case. Then, assumption for assumption, while keeping the other assumptions at base case, the NPV changes for each assumption in the worst- and best-case scenarios are checked.
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Pronghorn was originally developed for simulation of the gas-cooled pebble-bed VHTR concept. The current capabilities of Pronghorn include transient and steady coupled porous fluid flow and solid-state heat conduction with a standard multi-group diffusion model (i.e., fixed-source, criticality, and time-dependent). Recently added capabilities include a nonlinear acceleration scheme for criticality problems and a simple thermal- fluid model for the prismatic reactor concept.
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As a result, nations and other large institutions are increasingly analyzing a material's criticality and seek to minimize any risk, restriction, or environmental impact associated with the material.
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A 50 kW TRIGA MARK I reactor. Initial criticality June 6, 1959. The reactor was shut down June 29, 1970. It has been dismantled but not fully decommissioned.
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It has been observed that many criticality accidents emit a blue flash of light. The blue glow of a criticality accident results from the fluorescence of the excited ions, atoms and molecules of the surrounding medium falling back to unexcited states. This is also the reason electrical sparks in air, including lightning, appear electric blue. The smell of ozone was said to be a sign of high ambient radioactivity by Chernobyl liquidators.
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Initial criticality was achieved in January 1962, followed by wet criticality six months later. Difficulties that arose during operation and required plant shutdown and correction included leaking control rod thimbles, seizure of secondary sodium pumps, leaking steam generator instrumentation and pipe flanges, difficulty of adjusting fuel channel flow orifices, and failure of primary and secondary sodium throttle valves. The most serious issue was the ruptures of moderator elements. Seven elements ruptured in February, 1964.
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Construction started in 1986 and the reactor achieved criticality for the first time in April 1994. An accident in December 1995, in which a sodium leak caused a major fire, forced a shutdown. A subsequent scandal involving a cover-up of the scope of the accident delayed its restart until May 6, 2010, with renewed criticality reached on May 8, 2010. In August 2010 another accident, involving dropped machinery, shut down the reactor again.
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The TCE concept is related to the degree to which an element is seen to be critical. Criticality is related to scarcity, which, in turn, is related to any imbalance between supply and demand. Various attempts at the assessment of this criticality have taken place over recent years. In most cases, these assessments use a two-parameter matrix with slightly different definitions, but generally involving supply risk and vulnerability to restriction of that supply.
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While preparing enriched uranium fuel for use in the Jōyō experimental breeder reactor, a criticality occurred causing a criticality lasting 20 hours during which the nuclear fission chain reaction emitted intense gamma and neutron radiation. At least 667 workers, nearby residents and emergency response team members were exposed to excess radiation. Two technicians, Hisachi Ouchi and Masato Shinohara died from the accident. Radiation levels at the plant were 15,000 time higher than normal.
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Chain reactions naturally give rise to reaction rates that grow (or shrink) exponentially, whereas a nuclear power reactor needs to be able to hold the reaction rate reasonably constant. To maintain this control, the chain reaction criticality must have a slow enough time scale to permit intervention by additional effects (e.g., mechanical control rods or thermal expansion). Consequently, all nuclear power reactors (even fast-neutron reactors) rely on delayed neutrons for their criticality.
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Some people reported feeling a "heat wave" during a criticality event.McLaughlin et al. page 42, "the operator saw a flash of light and felt a pulse of heat."McLaughlin et al.
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Sanmen Unit 1 entered into commercial operation on September 21, 2018. Sanmen Unit 2 achieved first criticality on August 17, 2018 and was connected to the grid on August 24, 2018.
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Two workers died, a third was permanently injured, and 350 citizens were exposed to radiation. In 2016, a criticality accident was reported at the Afrikantov OKBM Critical Test Facility in Russia.
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Nuclear reactors can be susceptible to prompt- criticality accidents if a large increase in reactivity (or k-effective) occurs, e.g., following failure of their control and safety systems. The rapid uncontrollable increase in reactor power in prompt-critical conditions is likely to irreparably damage the reactor and in extreme cases, may breach the containment of the reactor. Nuclear reactors' safety systems are designed to prevent prompt criticality and, for defense in depth, reactor structures also provide multiple layers of containment as a precaution against any accidental releases of radioactive fission products. With the exception of research and experimental reactors, only a small number of reactor accidents are thought to have achieved prompt criticality, for example Chernobyl #4, the U.S. Army's SL-1, and Soviet submarine K-431.
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This is the critical size. Other parameters include: Temperature: This particular parameter is less common for the criticality safety practitioner, as in a typical operating environment, where the variation in temperature is minimal, or where the increase in temperature does not adversely affect the criticality of the system, often, it is assumed that room temperate is bounding of the actual temperature of the system being analyzed. This is however only an assumption, it is important for the criticality safety practitioner to understand where this not apply, such as high temperature reactors, or low temperature cryogenic experiments. Heterogeneity: Blending fissile powders into solution, milling of powders or scraps, or other processes that effects the small-scale structure of fissile materials is important.
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Reactor start up (criticality) is achieved by withdrawing control rods from the core to raise core reactivity to a level where it is evident that the nuclear chain reaction is self-sustaining. This is known as "going critical". Control rod withdrawal is performed slowly, as to carefully monitor core conditions as the reactor approaches criticality. When the reactor is observed to become slightly super-critical, that is, reactor power is increasing on its own, the reactor is declared critical.
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Without delayed neutrons, changes in reaction rates in nuclear reactors would occur at speeds that are too fast for humans to control. The region of supercriticality between k = 1 and k = 1/(1 − β) is known as delayed supercriticality (or delayed criticality). It is in this region that all nuclear power reactors operate. The region of supercriticality for k > 1/(1 − β) is known as prompt supercriticality (or prompt criticality), which is the region in which nuclear weapons operate.
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Vixen trials involved safety testing. They were about assuring that the core of a nuclear weapon would not accidentally undergo criticality in the event of a fire or unintended crash. These were messy, for a successful test subjected the core to high explosives in the hope that it simply scatters rather than undergoes criticality. These tests sometimes involved some yield from fission, but in every case this was less than the yield from the weapon's conventional explosive component.
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Two serious nuclear incidents happened at surrounding nuclear facilities. On 11 March 1997, a small explosion in a Dōnen plant. On 30 September 1999, a serious criticality accident in a JCO plant.
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Boric acid is airlifted to Fukushima for addition to cooling water. Despite widely voiced concerns, the evidence suggests that the spent fuel pool at Unit 4 did not approach criticality at any stage.
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Los Angeles Times, January 11, 2015. In August 2017, the improper storage of plutonium metal could have triggered a criticality accident, and subsequently staff failed to declare the failure as required by procedure.
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This hypothesis also provides for an alternative paradigm to explain power law manifestations that have been attributed to self-organized criticality. There are various mathematical models to create pink noise. Although self-organised criticality has been able to reproduce pink noise in sandpile models, these do not have a Gaussian distribution or other expected statistical qualities. It can be generated on computer, for example, by filtering white noise, inverse Fourier transform, or by multirate variants on standard white noise generation.
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He was from 2014 to 2015 at ETH Zurich and from 2015 to 2016 a visiting professor in Geneva. His research deals with conformal invariance of two-dimensional lattice models at criticality, specifically the Ising models of statistical mechanics, in which he showed universality and conformal invariance at criticality with the Fields medalist Stanislav Smirnov. Chelkak also does research on spectral theory, especially inverse spectral problems of one- dimensional differential operators. In 1995 he received the gold medal at the International Mathematical Olympiad.
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In the operation of a nuclear reactor, criticality is the state in which a nuclear chain reaction is self-sustaining—that is, when reactivity is zero. In supercritical states, reactivity is greater than zero.
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A 1 MW TRIGA MARK II reactor. Initial criticality March 24, 1972. The reactor has been in extended shutdown since 2004. The reactor was used for training, fundamental research, isotope production and material characterization.
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If no big component exists, the model is said to be subcritical. The conditions of giant component criticality naturally depend on parameters of the model such as the density of the underlying point process.
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Self-organized criticality is an abrupt disturbance in a system resulting from a buildup of events without external stimuli. Examples of pattern types: # Abrupt changes in feeding activity. # Mechanical grasping of legs forming ant droplets.
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The electrical equipment was supplied by Strömberg. Unit 1 was constructed by Atomirakennus and unit 2 by Jukola and Työyhtymä. Unit 1 achieved its initial criticality in July 1978 and it started commercial operations in October 1979. Unit 2 achieved its initial criticality in October 1979 and it started commercial operations in July 1982. The original power of the reactors was 660 MW. They were uprated to 710 MW in 1983–1984, to 840 MW in 1995–1998, and further to 860 MW in 2005–2006.
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Failure mode effects and criticality analysis (FMECA) is an extension of failure mode and effects analysis (FMEA). FMEA is a bottom-up, inductive analytical method which may be performed at either the functional or piece- part level. FMECA extends FMEA by including a criticality analysis, which is used to chart the probability of failure modes against the severity of their consequences. The result highlights failure modes with relatively high probability and severity of consequences, allowing remedial effort to be directed where it will produce the greatest value.
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Criticality as a signature of healthy neural systems: multi-scale experimental and computational studies (2015) Experimental recordings from large groups of neurons have shown bursts of activity, so-called neuronal avalanches, with sizes that follow a power law distribution. These results, and subsequent replication on a number of settings, led to the hypothesis that the collective dynamics of large neuronal networks in the brain operates close to the critical point of a phase transition.Beggs, John M., Timme, Nicholas. Being critical of criticality in the brain.
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While the institution provides the site and some initial requirements, the government brings in resources adequate enough to overcome the sub-criticality and the user organizations bring in resources as well as relevance to the efforts.
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Edson hall, the location of the Communications School at Marine Corps Base Quantico in Virginia, is dedicated to Edson as a result of his role as a vocal proponent of the criticality of communications in combat.
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When the control rods are withdrawn and criticality is approached the number increases because the absorption of neutrons is being progressively reduced, until at criticality the chain reaction becomes self-sustaining. Note that while a neutron source is provided in the reactor, this is not essential to start the chain reaction, its main purpose is to give a shutdown neutron population which is detectable by instruments and so make the approach to critical more observable. The reactor will go critical at the same control rod position whether a source is loaded or not. Once the chain reaction is begun, the primary starter source may be removed from the core to prevent damage from the high neutron flux in the operating reactor core; the secondary sources usually remains in situ to provide a background reference level for control of criticality.
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The school operates the 200 kW Missouri S&T; nuclear reactor on-campus for educational, training, and research purposes. It became the first nuclear reactor to have become operational in Missouri, and first achieved criticality in 1961.
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The manner in which these sets can be divided determine the Hausdorff dimension of the set, which is generally different from the more familiar topological dimension. Fractal phenomena are associated with chaos, self-organized criticality and turbulence.
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The first reactor of the plant attained criticality on 13 July 2013 and was connected to the grid three months later. Kudankulam nuclear plant begins power generation. Mumbai Mirror (2013-10-22). Retrieved on 2013-12-06.
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Angela Helen Clayton MBE (1959 - 8 January 2014Legacy.com. Archived at ) was an internationally known physicist working in the fields of Nuclear Criticality Safety and Health Physics. She was also a campaigner for the rights of transgender people.
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A criticality accident (also sometimes referred to as an "excursion" or "power excursion") occurs when a nuclear chain reaction is accidentally allowed to occur in fissile material, such as enriched uranium or plutonium. The Chernobyl accident is not universally regarded an example of a criticality accident, because it occurred in an operating reactor at a power plant. The reactor was supposed to be in a controlled critical state, but control of the chain reaction was lost. The accident destroyed the reactor and left a large geographic area uninhabitable.
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TEPCO confirmed its concern about the accuracy of the high iodine and chlorine report by formally retracting the report on 21 April, which eliminated both the exceptionally high iodine-134 and chlorine-38 levels as proof of criticality. TEPCO did not appear to comment on the criticality concern when withdrawing its report, but the IAEA has not withdrawn its comments, and some off-site experts find the currently measured iodine-134 levels higher than expected.After 5 Halflives, I-131 Higher than Cs-134/137 Suggests Ongoing Criticalities – GLG News. Glgroup.
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A critical fission would have caused much higher concentrations of xenon isotopes. These reactions would occur constantly, and did not lead to criticality in the melted fuel of reactor 2. All assessments would be sent to NISA for reevaluation.NHK-world (3 November 2011) TEPCO retracts criticality call JAIF (3 November 2011)Earthquake-report 255 The Mainichi Daily News (4 November 2011) Xenon at Fukushima not result of 'critical' nuclear reactions: TEPCO The detection of xenon on the afternoon of 1 November by TEPCO was reported to NISA in the night.
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Due to its inherent flexibility, RAMP is now used to optimise system design and support critical decision making in many sectorsReliability, Maintainability and Risk: 7th Edition. Elsevier. David J. Smith BSc PhD CEng FIEE FIQA HonFSaRS MIGasE. RAMP provides the capability to model many factors that may affect a system such as changes in specification or procurement contracts, 'what if' studies, sensitivity analysis, equipment redundancy, equipment criticality, delayed failures, as well as allowing the generation of results that can be exported for failure mode, effects and criticality analysis (FMECA) and cost-benefit analysis.
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In order to maintain criticality, the fuel has to retain that extra concentration of U-235. A typical fission reactor burns off enough of the U-235 to cause the reaction to stop over a period on the order of a few months. A combination of burnup of the U-235 along with the creation of neutron absorbers, or poisons, as part of the fission process eventually results in the fuel mass not being able to maintain criticality. This burned up fuel has to be removed and replaced with fresh fuel.
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The sampling system can be an 'open-frame free standing' type design or a fully or partially closed design, depending on the choice of the user, the environment it is supposed to operate in & the criticality of operation.
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This threshold is called the critical mass. Absorption: Absorption removes neutrons from the system. Large amounts of absorbers are used to control or reduce the probability of a criticality. Good absorbers are boron, cadmium, gadolinium, silver, and indium.
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All three men succumbed to injuries from physical trauma; however, the radiation from the nuclear excursion would have given the men no chance of survival even had they not been killed by the explosion stemming from the criticality accident.
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The OPA model is used to study different techniques for criticality control. # Cascading failure in the internet switching fabric. # Ischemic cascades, a series of biochemical reactions releasing toxins during moments of inadequate blood supply. # Systemic risk in financial systems.
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The HKB model, which has also been elucidated by several complex mathematical descriptors, is still a relatively simple but powerful way to describe seemingly-independent systems that come to reach synchrony just before a state of self-organized criticality.
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Complexity and Postmodernism: Understanding Complex Systems, Routledge, London. This is referred to as the "edge of chaos".Per Bak (1996). How Nature Works: The Science of Self- Organized Criticality, Copernicus, New York, U.S. A plot of the Lorenz attractor.
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There have been two Tokaimura nuclear accidents at the nuclear facility at Tōkai, Ibaraki, Japan: on 11 March 1997, an explosion occurred in a Dōnen plant, and on 30 September 1999, a serious criticality accident happened in a JCO plant.
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Surrounding a spherical critical mass with a neutron reflector further reduces the mass needed for criticality. A common material for a neutron reflector is beryllium metal. This reduces the number of neutrons which escape the fissile material, resulting in increased reactivity.
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Criticality was achieved in September 1959 with final shutdown completed in December 1961. The project was considered a success. It gave continued confidence in the development of the SNAP Program and it also led to in depth research and component development.
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Fractal curves and fractal patterns are widespread, in nature, found in such places as broccoli, snowflakes, feet of geckos, frost crystals, and lightning bolts. See also Romanesco broccoli, dendrite crystal, trees, fractals, Hofstadter's butterfly, Lichtenberg figure, and self-organized criticality.
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This concept was proposed for a reactor whose purpose was to test the behavior of materials under neutron flux. This reactor, the Material Testing Reactor (MTR), was built in Idaho at INL and reached criticality on March 31, 1952. For the design of this reactor, experiments were necessary, so a mock-up of the MTR was built at ORNL, to assess the hydraulic performances of the primary circuit and then to test its neutronic characteristics. This MTR mock-up, later called the Low Intensity Test Reactor (LITR), reached criticality on February 4, 1950 and was the world's first light-water reactor.
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Majeed returned to Pakistan in 1974 after India had conducted a surprise nuclear test, codenamed "Pokhran-I". At the Pakistan Institute of Nuclear Science and Technology (PINSTECH) he was assigned to the Nuclear Chemistry Division led by Iqbal Hussain Qureshi. In 1974, Majeed was a part of Munir Ahmad Khan's team that had supervised the criticality of the second nuclear pile —PARR-II reactor. After the construction of the third nuclear pile—PARR-III, also known as The New-Labs; Majeed was the first technical director, and was part of a team that supervised the reactor's criticality.
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In one set of experiments the solution was in tanks without a surrounding reflector. Solution heights were adjusted to criticality with D2O solutions at D/235U atomic ratios of 1:230 and 1:419 in the smaller tank and 1:856 to 1:2081 in the larger tank. In the other set of experiments solution spheres were centered in a spherical container into which D2O was pumped from a reservoir at the base. Criticality was attained in six solution spheres from 13.5- to 18.5-inch diameter at D/235U atomic ratios from 1:34 to 1:431.
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Traditional safety-critical systems had to be tested and certified in their entirety to show that they were safe to use. However, many such systems are composed of a mixture of safety-critical and non-critical parts, as for example when an aircraft contains a passenger entertainment system that is isolated from the safety-critical flight systems. Some issues to address in mixed criticality systems include real-time behaviour, memory isolation, data and control coupling. Computer scientists have developed techniques for handling systems which thus have mixed criticality, but there are many challenges remaining especially for multi-core hardware.
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The primary benefits were to qualitatively evaluate the safety and reliability of a system, determine unacceptable failure modes, identify potential design improvements, plan maintenance activities and help understand system operation in the presence of potential faults. The failure modes, effects and criticality analysis (FMECA) was introduced to address a primary barrier to effective use of the detailed FMEA results by the addition of a criticality metric. This allowed users of the analysis to quickly focus on the most important failure modes/effects in terms of risk. This allowed prioritization to drive improvements based on cost / benefit comparisons.
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The site was chosen and plans to build the station were announced in 1969, by the Philadelphia Electric Company (now PECO Energy, a subsidiary of Exelon). It is located approximately one mile south of Sanatoga, PA. Community protests by the Keystone Alliance and other delays pushed the start of construction by the Bechtel Power Corporation to June 1974. Limerick Unit 1 first attained criticality (began producing nuclear power, at limited capacity) on December 22, 1984 and was certified for commercial operation on February 1, 1986. Limerick Unit 2 attained criticality on August 1, 1989, and commercial operation began on January 8, 1990.
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The hollow ring shape of this plutonium ingot favors neutron leakage and thus reduces the likelihood of criticality. As a simplistic analysis, a system will be exactly critical if the rate of neutron production from fission is exactly balanced by the rate at which neutrons are either absorbed or lost from the system due to leakage. Safely subcritical systems can be designed by ensuring that the potential combined rate of absorption and leakage always exceeds the potential rate of neutron production. The parameters affecting the criticality of the system may be remembered using the mnemonic MAGICMERV.
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Frontiers in Physiology, 07, June 2012 According to this hypothesis, the activity of the brain would be continuously transitioning between two phases, one in which activity will rapidly reduce and die, and another where activity will build up and amplify over time. In criticality, the brain capacity for information processing is enhanced,Beggs, J. M. The criticality hypothesis: how local cortical networks might optimize information processing. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 366, 329–343 (2008). so subcritical, critical and slightly supercritical branching process of thoughts could describe how human and animal minds function.
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The project commenced in 1956, and construction began January 1, 1960. First criticality followed on March 11, 1966 (the reactor was not pressurised at that time however). Full start-up was on May 9, and commercial power production began on October 11, 1966.
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In dynamics, all continuous time dynamical systems, with and without noise, are Witten-type TQFTs and the phenomenon of spontaneous breakdown of the corresponding topological supersymmetry encompasses such well-established concepts as chaos, turbulence, 1/f and crackling noises, self-organized criticality etc.
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The energy of delayed neutrons is so low that contribution to fission is almost 0.0000, requiring some fissile material to keep the reactor safely under prompt criticality: (e.g. in natural uranium and preferably also some moderator, possibly outside the extra-fast core).
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MacDonald is a presenter at conferences in North America, Europe and Asia on the criticality of resources deemed strategic for high tech, green energy and the rapidly evolving grid level mass storage and electric vehicle battery industries. He currently resides in Vancouver, B.C.
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Land for the plant was bought in 1965 by the energy company Sydkraft, and the first of the two BWR reactors was ordered from Asea-Atom in 1969. Unit one first attained criticality on January 18, 1975 and commercial operation began on May 15.
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It began commercial operation on 6 June. On 23 November 2013 Hongyanhe 2 was connected to the grid. Hongyanhe 4 achieved first criticality on 5 March 2016, was connected to the grid on 1 April 2016, and entered commercial operation on 20 September 2016.
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The construction began on 23 January 1973, and suffered from many delays. After construction was halted on both units in 1985, construction resumed on Unit 1 in 1992. First criticality was achieved on 1 January 1996 and commercial operation began on May 5, 1996.
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In the context of software quality, defect criticality is a measure of the impact of a software defect. It is defined as the product of severity, likelihood, and class. Defects are different from user stories, and therefore the priority (severity) should be calculated as follows.
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In January 2017 the plant took delivery of a safety instrumentation and control system from Areva NP for installation in its Unit 1. The first criticality of Unit 2 reactor was achieved on 22 March 2019, with connection to the grid on 1 May 2019.
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These difficulties—among many others— prevented the Nazis from building a nuclear reactor capable of criticality during the war, although they never put as much effort as the United States into nuclear research, focusing on other technologies (see German nuclear energy project for more details).
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In 1987, he and two postdoctoral researchers, Chao Tang and Kurt Wiesenfeld, published an article in Physical Review Letters setting a new concept they called self-organized criticality. The first discovered example of a dynamical system displaying such self-organized criticality, the Bak-Tang-Wiesenfeld sandpile model, was named after them. Faced with many skeptics, Bak pursued the implications of his theory at a number of institutions, including the Brookhaven National Laboratory, the Santa Fe Institute, the Niels Bohr Institute in Copenhagen, and Imperial College London, where he became a professor in 2000. In 1996, he took his ideas to a broader audience with his ambitiously entitled book, How Nature Works.
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TVA declared construction substantially complete in August 2015 and requested that NRC staff proceed with the final licensing review; on October 22, the NRC approved a forty-year operating license for Unit 2, marking the formal end of construction and allowing for the installation of nuclear fuel and subsequent testing. On December 15, 2015, TVA announced that the reactor was fully loaded with fuel and ready for criticality and power ascension tests. In March 2016, the Nuclear Regulatory Commission described the project as a "chilled work environment," where employees are reluctant to raise safety concerns for fear of retribution. On May 23, 2016, initial criticality was achieved.
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During its construction, a total of 3.8 lakh (380,000) railway sleeper (logs) were brought from all over India to lift the 180 ton critical equipment in the first unit, due to lack of proper infrastructure and handling equipment. the Prototype Fast Breeder Reactor (PFBR) was in its final construction stage, and was expected to reach criticality in March 2017 with 500 MW of electricity production. The following month the loading of the 1750 ton liquid sodium coolant were expected to happen in four to five months, with sources in the Department of Atomic Energy reporting that criticality would likely be reached only around May 2017.
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He invented a new method of computing logarithms that he later used on the Connection Machine. Other work at Los Alamos included calculating neutron equations for the Los Alamos "Water Boiler", a small nuclear reactor, to measure how close an assembly of fissile material was to criticality. On completing this work, Feynman was sent to the Clinton Engineer Works in Oak Ridge, Tennessee, where the Manhattan Project had its uranium enrichment facilities. He aided the engineers there in devising safety procedures for material storage so that criticality accidents could be avoided, especially when enriched uranium came into contact with water, which acted as a neutron moderator.
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This was unproven, and was in any case an argument that did not apply to a "Criticality 1" component. As astronaut Sally Ride stated when questioning NASA managers before the Rogers Commission, it is forbidden to rely on a backup for a "Criticality 1" component. NASA claimed that it did not know of Thiokol's earlier concerns about the effects of the cold on the O-rings, and did not understand that Rockwell International, the shuttle's prime contractor, additionally viewed the large amount of ice present on the pad as a constraint to launch. According to Ebeling, a second conference call was scheduled with only NASA and Thiokol management, excluding the engineers.
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Steeped in Exploration (2010) - “A Teahouse without Tea!” – is a socially engaged art project aimed at creating space for dialogues around exploring the “local”, science, public involvement, ecological issues, community building, artists’ sensibilities, bringing criticality to space, and dissecting the systems that make up our “everyday” life.
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Research at the Massachusetts Institute of Technology suggests that there is evidence that the frequency of stock market crashes follows an inverse cubic power law. This and other studies such as Didier Sornette's work suggest that stock market crashes are a sign of self- organized criticality in financial markets.
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With the exception of those two, all other isotopes have half-lives under a minute, most under a second. The shortest-lived is , with a half-life of seconds. Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable in human blood plasma to .
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On November 14, 2017, the TREAT reactor achieved criticality for the first time since 1994. This was accomplished 12 months ahead of schedule, and about $20 million under budget. This is an important milestone toward the testing of new nuclear fuel, which is expected to begin in 2018.
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Neither type had previously been tested in a nuclear rocket propulsion reactor. In all, this was about 5 kg of highly enriched (93%) uranium-235. To achieve criticality with so little fuel, the beryllium reflector was over thick. Each fuel cell had its own cooling and moderating water jacket.
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Three major nuclear-related accidents have occurred at LANL. Criticality accidents occurred in August 1945 and May 1946, and a third accident occurred during an annual physical inventory in December 1958. Several buildings associated with the Manhattan Project at Los Alamos were declared a National Historic Landmark in 1965.
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This style of reactor can be designed to be inherently safe. As it heats, the graphite expands, separating the fuel and reducing the reactor's criticality. This property can simplify the operating controls to a single valve throttling the turbine. When closed, the reactor heats, but produces less power.
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Criticality is accomplished by concentrating, or enriching, the fuel, increasing the amount of U-235 to produce enriched uranium, while the leftover, now mostly U-238, is a waste product known as depleted uranium. U-235 will undergo fission more easily if the neutrons are of lower energy, the so-called thermal neutrons. Neutrons can be slowed to thermal energies through collisions with a neutron moderator material, the most obvious being the hydrogen atoms found in water. By placing the fission fuel in water, the probability that the neutrons will cause fission in another U-235 is greatly increased, which means the level of enrichment needed to reach criticality is greatly reduced.
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At Los Alamos, Slotin's duties consisted of dangerous criticality testing, first with uranium in Otto Robert Frisch's experiments, and later with plutonium cores. Criticality testing involved bringing masses of fissile materials to near-critical levels to establish their critical mass values. Scientists referred to this flirting with the possibility of a nuclear chain reaction as "tickling the dragon's tail", based on a remark by physicist Richard Feynman, who compared the experiments to "tickling the tail of a sleeping dragon". On 16 July 1945, Slotin assembled the core for Trinity, the first detonated atomic device, and became known as the "chief armorer of the United States" for his expertise in assembling nuclear weapons.
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The Criticality Index is often used to determine the degree on condition monitoring on a given machine taking into account the machines purpose, redundancy (i.e. if the machine fails, is there a standby machine which can take over), cost of repair, downtime impacts, health, safety and environment issues and a number of other key factors. The criticality index puts all machines into one of three categories: # Critical machinery – Machines that are vital to the plant or process and without which the plant or process cannot function. Machines in this category include the steam or gas turbines in a power plant, crude oil export pumps on an oil rig or the cracker in an oil refinery.
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Due to poor design and maintenance procedures, a single control rod was manually pulled out too far from the reactor, causing the reactor to become prompt critical, leading to a destructive power excursion. Three trained military men had been working inside the reactor room when a mistake was made while reattaching a control rod to its motor assembly. See summary: With the central control rod nearly fully extended, the nuclear reactor rated at 3 MW rapidly increased power to 20 GW. This rapidly boiled the water inside the core.LA-3611 A Review of Criticality Accidents, William R. Stratton, Los Alamos Scientific Laboratory, 1967LA-13638 A Review of Criticality Accidents (2000 Revision), Thomas P. McLaughlin, et al.
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On 3 February 1954 and 12 February 1957, accidental criticality excursions occurred causing damage to the device, but only insignificant exposures to personnel. This original Godiva device, known as Lady Godiva, was irreparable after the second accident and was replaced by the Godiva II.McLaughlin et al. pages 78, 80-83.
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In systems in equilibrium, the critical point is reached only by precisely tuning a control parameter. However, in some non- equilibrium systems, the critical point is an attractor of the dynamics in a manner that is robust with respect to system parameters, a phenomenon referred to as self-organized criticality.
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It now serves as the Criticality Experiments Facility (CEF). The Control Point is the communication hub of the NTS. It was used by controllers to trigger and monitor nuclear test explosions. In 1982, while a live nuclear bomb was being lowered underground, the base came under attack by armed combatants.
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Recognizing that criticality is one reason that complementary, terrestrial eLORAN is attracting interest. Tight coupling of sensors and precision attack might shift frameworks to a "halting" rather than a "buildup" or "counterattack" framework. Gaming can explore the intelligence requirements to know what are the centers of gravity for halting frameworks.
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The 69 MWe prototype fast breeder reactor Fermi 1 unit was under construction and development at the site from 1956 to 1963. Initial criticality was achieved on August 23, 1963. On October 5, 1966 Fermi 1 suffered a partial fuel meltdown. Two of the 92 fuel assemblies were partially damaged.
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As an organic solvent was added to the aqueous solution in the vessel, the organic and aqueous phases separated out with the organic layer on top. This solvent extracted plutonium from the aqueous solution with sufficient concentration and geometry to create a criticality. Two plant workers were exposed to radiation.
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Scarville was platted in 1899, and incorporated as a city in 1904. The city was named for Ole Scar, a local landowner. In 1973, investigators from the United States Atomic Energy Commission investigated a possible criticality accident on a railcar at the local grain elevator, but nothing conclusive was found.
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On 27 December 2015 and 7 September 2016, CNNC started construction of Units 5 and 6 with their own 1,000 MW ACPR-1000 reactors. Fuel loading for Tianwan unit 5 was completed on 13 July 2020, criticality was achieved on 30 July 2020, and grid connection was established on 8 August 2020.
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Primary functions of the Program Management Office include advocating on behalf of the NSI, providing guidance to participants at all levels, and coordinating various efforts within the NSI. Given the criticality of privacy and civil liberties issues, the PMO works collaboratively with, and is supported by, the DOJ Privacy and Civil Liberties Office.
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Extremal optimization (EO) is an optimization heuristic inspired by the Bak–Sneppen model of self-organized criticality from the field of statistical physics. This heuristic was designed initially to address combinatorial optimization problems such as the travelling salesman problem and spin glasses, although the technique has been demonstrated to function in optimization domains.
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'Urchin' initiated the nuclear chain reaction at the moment of prompt-criticality to ensure that the weapon did not fizzle. 'Urchin' was used in early U.S. weapons; subsequent U.S. weapons utilized a pulse neutron generator for the same purpose. Much of the basic physics of polonium was classified until after the war.
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In December 2019, the first unit started hot trials, checking the reactor unit under hot conditions, but with dummy fuel rods placed in the reactor. The tests were completed in April 2020. Fuel loading for the first unit started on 7 August 2020. On 11 October 2020, Unit 1 achieved first criticality.
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The converted reactor achieved criticality in April 1988. The converted PRR-1 TRIGA reactor used low-enriched uranium instead of highly enriched uranium. After its conversion, technical and administrative problems rendered the facility inoperable, which resulted in its extended shutdown. In 2005, it was initially decided that the reactor would be decommissioned.
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Most companies that use cost based pricing realize the pitfalls and try to soften the impact by never lowering prices with cost reductions, but only increasing them when costs run too high. If they encounter price resistance in the market, they deal with it by providing discounts based on customer relationship or order volume or order criticality etc. However, when customers are rewarded with discounts for their price resistance, the resistance becomes more frequent even when the product is valuable for them.Strategy and Tactics of Pricing Nagle & Homan (2006) Even when used in conjunction with part segmentation on business groups, part lifecycle and part criticality to decide more granular markups on cost, the approach still tends to generate prices that are not simple to comprehend for customers.
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During the regime of president Marcos Pérez Jiménez, the RV-1 nuclear reactor at IVIC, was commissioned under the supervision of Humberto Fernández-Morán. The reactor was purchased from General Electric in 1956 and could produce up to 3 MW of power. The reactor reached criticality in 1960 and was shut down in 1994.
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The integral fast reactor was developed at the West Campus of the Argonne National Laboratory in Idaho Falls, Idaho and was the intended successor to the Experimental Breeder Reactor II, which achieved first criticality in 1965 and ran for 30 years. The Integral Fast Reactor project was shut down by the U.S. Congress in 1994.
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Monju reactor clears hurdle to restart. Feb 23, 2010. In late February, JAEA requested Fukui Prefecture and Tsuruga City for deliberations aimed at resuming test operation. Having obtained the go ahead from both entities, JAEA started criticality testing, after which it took some months before commercial operation could resume – as for any new nuclear plant.
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Trillo Nuclear Power Plant is a nuclear power station in Spain. It consists of one pressurized water reactor (PWR) of 1066 MWe. Construction of unit one began in 1979, and first criticality was on 14 May 1988. A planned second identical unit was cancelled soon after construction began following a change of government in 1983.
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Fermi 2 is a 1,202 MWe General Electric boiling water reactor owned and operated by DTE Energy. Plans to build were announced in July 1968. Initial criticality was achieved in July 1985, and full commercial operation commenced on January 23, 1988.NRC "Fermi, Unit 2", NRC Website, 13 January 2011, accessed 17 March 2011.
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These controls, either passive (physical), active (mechanical), or administrative (human), are implemented by inherently safe or fault-tolerant plant designs, or, if such designs are not practicable, by administrative controls such as operating procedures, job instructions and other means to minimize the potential for significant process changes that could lead to a nuclear criticality accident.
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BN-800 underwent a major redesign in 1987, and a more minor one in 1993, but construction did not restart until 2006. The reactor did not reach criticality until 2014, and further progress stopped due to problems with the fuel design. It restarted in 2015, and reached full power in August 2016, entering commercial operation.
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The International Atomic Energy Agency safeguards the reactor. It was inaugurated by the second President of Indonesia, Suharto on August 20, 1987. The reactor was named after G.A. Siwabessy, Minister of Health and Minister of Atomic Energy under both president Sukarno and Suharto. RSG-GAS went to its first criticality on July 29, 1987.
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The neutrons are usually classified in 6 delayed neutron groups. The average neutron lifetime considering delayed neutrons is approximately 0.1 sec, which makes the chain reaction relatively easy to control over time. The remaining 993 prompt neutrons are released very quickly, approximately 1 μs after the fission event. In steady-state operation, nuclear reactors operate at exact criticality.
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Image of a 60-inch cyclotron, circa 1939, showing an external beam of accelerated ions (perhaps protons or deuterons) ionizing the surrounding air and causing an ionized-air glow. Due to the similar mechanism of production, the blue glow is thought to resemble the "blue flash" seen by Harry Daghlian and other witnesses of criticality accidents.
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A subcritical reactor is a nuclear fission reactor concept that produces fission without achieving criticality. Instead of sustaining a chain reaction, a subcritical reactor uses additional neutrons from an outside source. There are two general classes of such devices. One uses neutrons provided by a nuclear fusion machine, a concept known as a fusion–fission hybrid.
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The concept of function criticality was replaced with classification of failure conditions according to severity of effects (cf., Probabilistic risk assessment). Failure conditions having Catastrophic, Major, or Minor effects were to have restricted likelihoods, respectively, of Extremely Improbable (10-9 or less), Improbable (10-5 or less), or no worse than Probable (10-5).AC 25.1309-1A, pp.
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The successful demonstration of the Romashka reactor provided a baseline for further developments in Soviet nuclear power for space satellites. The experimental reactor was started (reached criticality) in 1964 and decommissioned in 1966, and was used to research the concept of direct energy conversion. It produced of heat, and reached temperatures of .The reactor operated for .
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Optical materials deteriorate under the effect of ionizing radiation. High-intensity ionizing radiation in air can produce a visible ionized air glow of telltale bluish-purple color. The glow can be observed, e.g., during criticality accidents, around mushroom clouds shortly after a nuclear explosion, or the inside of a damaged nuclear reactor like during the Chernobyl disaster.
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Dante R. Chialvo (born 1956) is a professor at Universidad Nacional de San Martin. Together with Per Bak, they put forward concrete models considering the brain as a critical system. Initial contributions focussed on mathematical ideas of how learning could benefit from criticality. Further work provided experimental evidence for this conjecture both at large and small scale.
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Chicago Pile team in 1946; Lichtenberger is in the middle row, third from the left. Harold V. Lichtenberger (April 22, 1920 – December 7, 1993) was an American physicist who was involved in the planning of the Chicago Pile-1, the first nuclear reactor to achieve criticality, and in other reactor experiments at the Argonne National Laboratory.
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Criticality occurs when sufficient fissile material (a critical mass) accumulates in a small volume such that each fission, on average, produces a neutron that in turn strikes another fissile atom causing another fission; this causes the chain reaction to become self-sustaining within the mass of material. In other words, the number of neutrons emitted, over time, exceeds the number of neutrons captured by another nucleus or lost to the environment, resulting in a cascade of increasing nuclear fissions. Criticality can be achieved by using metallic uranium or plutonium, liquid solutions, or powder slurries. The chain reaction is influenced by range of parameters noted by the acronyms MAGIC MERV (for Mass, Absorption, Geometry, Interaction, Concentration, Moderation, Enrichment, Reflection, and Volume) and MERMAIDS (for Mass, Enrichment, Reflection, Moderation, Absorption, Interaction, Density, and Shape).
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Kurt Wiesenfeld received his Bachelor of Science in Physics from the Massachusetts Institute of Technology in 1979, after which he moved to University of California, Berkeley and received his doctorate in 1985. From 1984 to 1985 he was a Lecturer and Research Scientist at the University of California at Santa Cruz. In 1987, as a post-doctoral research scientist in the Solid State Theory Group of Brookhaven National Laboratory, he and another fellow post-doctoral scientist, Chao Tang, along with their mentor, Per Bak, presented new ideas in group organization with a concept they coined self-organized criticality in their paper in Physical Review Letters. The first discovered example of a dynamical system displaying such self- organized criticality was named after them as the Bak–Tang–Wiesenfeld "sandpile" model.
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In the design of nuclear weapons, on the other hand, achieving prompt criticality is essential. Indeed, one of the design problems to overcome in constructing a bomb is to compress the fissile materials enough to achieve prompt criticality before the chain reaction has a chance to produce enough energy to cause the core to expand too much. A good bomb design must therefore win the race to a dense, prompt critical core before a less-powerful chain reaction disassembles the core without allowing a significant amount of fuel to fission (known as a fizzle). This generally means that nuclear bombs need special attention paid to the way the core is assembled, such as the implosion method invented by Richard C. Tolman, Robert Serber, and other scientists at the University of California, Berkeley in 1942.
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And so using ordinary water as a moderator will easily absorb so many neutrons that too few are left to sustain a chain reaction with the small isolated 235U nuclei in the fuel, thus precluding criticality in natural uranium. Because of this, a light-water reactor will require that the 235U isotope be concentrated in its uranium fuel, as enriched uranium, generally between 3% to 5% 235U by weight (the by-product from this process enrichment process is known as depleted uranium, and so consisting mainly of 238U, chemically pure). The degree of enrichment needed to achieve criticality with a light-water moderator depends on the exact geometry and other design parameters of the reactor. One complication of this approach is the need for uranium enrichment facilities, which are generally expensive to build and operate.
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The Missouri University of Science and Technology Nuclear Reactor (MSTR or Missouri S&TR;) is a swimming pool type nuclear reactor operated by the Missouri University of Science and Technology (Missouri S&T;). It first achieved criticality in 1961, making it the first operational nuclear reactor in the state of Missouri. Missouri S&T; operates this reactor for training, education, and research purposes.
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The pool- type reactor having a capacity of 1 MW that was named TR-1, achieved criticality on January 6, 1962 at 19:14 local time. After serving 15-year long for the production of radioisotopes and the neutronics experiments with the help of beam tubes, the TR-1 was shut down in September 9, 1977 as its capacity became insufficient.
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AC 25.1309-1 recommended that top-down analysis should identify each system function and evaluate its criticality, i.e., either non-essential, essential, or critical. The terms Error, Failure, and Failure Condition were defined. Functions were classified Critical, Essential, and Non-Essential according to the severity of the failure conditions they could contribute to; but the conditions were not expressly classified.
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Garigliano Nuclear Power Plant was a nuclear power plant located at Sessa Aurunca (Campania), in southern Italy. It was named after the river Garigliano. Consisting of one 150MWe BWR from General Electric, it operated from 1964 until 1982. First criticality was on 5 June 1963, with grid connection 1 January 1964 and full commercial operation from 1 June in that year.
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This reduces it to a diffusion problem. However, as the typical linear dimensions are not significantly larger than the mean free path, such an approximation is only marginally applicable. Finally, note that for some idealized geometries, the critical mass might formally be infinite, and other parameters are used to describe criticality. For example, consider an infinite sheet of fissionable material.
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The Douglas Point reactor first attained criticality on 15 November 1966 at 16:26 hours. It began feeding power into the grid on 7 January 1967 and officially entered service on 26 September 1968 with a 54% capacity factor. The plant made its first on-power fuelling (i.e. refuelling the reactor without having to shut down) on 1 March 1970.
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Unit Two achieved criticality on 6 May 2007 and was connected to the national grid on 7 August. It began operating at full capacity on 12 September 2007, also producing 706 MW. In the late 1990s, several reactors were built by AECL in South Korea. Wolsong 2 was commissioned July 1, 1997. Wolsong 3 was commissioned on July 1, 1998.
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An MSR was operated at the Critical Experiments Facility of the Oak Ridge National Laboratory in 1957. It was part of the circulating-fuel reactor program of the Pratt & Whitney Aircraft Company (PWAC). This was called Pratt and Whitney Aircraft Reactor-1 (PWAR-1). The experiment was run for a few weeks and at essentially zero power, although it reached criticality.
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Dora Epstein-Jones is an educator, historian and theorist of architecture. Epstein-Jones has a Ph.D., in Architectural History, Theory and Criticism from the University of California, Los Angeles and an M.A. Urban Planning, from UCLA. She is currently the chair of the Texas Tech University College of Architecture. Her work explores the boundaries of architecture's discipline, questions of practice, gender and criticality.
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Dual phase evolution is related to the well-known phenomenon of self-organized criticality (SOC). Both concern processes in which critical phase changes promote adaptation and organization within a system. However, SOC differs from DPE in several fundamental ways. Under SOC, a system's natural condition is to be in a critical state; in DPE a system's natural condition is a non-critical state.
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Operation Crossroads Test Able, a 23-kiloton air-deployed nuclear weapon detonated on July 1, 1946. This bomb used, and consumed, the infamous Demon core that took the lives of two scientists in two separate criticality accidents. Anti-nuclear demonstration in Colmar, north-eastern France, on October 3, 2009. Liquidators' portraits used for an anti-nuclear power protest in Geneva.
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They concluded that the deposit had been in a reactor: a natural nuclear fission reactor, around 1.8 to 1.7 billion years BP – in the Paleoproterozoic Era during Precambrian times. At that time the natural uranium had a concentration of about 3% 235U, and could have reached criticality with natural water as neutron moderator allowed by the special geometry of the deposit.
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Serbia presently doesn't have any nuclear power plants. Previously, Vinča Nuclear Institute operated two research reactors; RA and RB. The research reactors were supplied by the USSR. The larger of the two reactors was rated at 6.5 MW and used Soviet-supplied 80% enriched uranium fuel. On 15 October 1958, there was a criticality accident at one of the research reactors.
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In 2004 he was awarded the "Young Mathematician" Prize of the St. Petersburg Mathematical Society. In 2008 he received the Pierre Deligne Prize in Moscow. In 2014 he received the Salem Prize. In 2018 was an invited speaker at the International Congress of Mathematicians in Rio de Janeiro with talk Planar Ising model at criticality: state-of-the-art and perspectives.
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Other UPS schemes may use an internal combustion engine or turbine to supply power during a utility power outage and the amount of battery time is then dependent upon how long it takes the generator to be on line and the criticality of the equipment served. Such a scheme is found in hospitals, data centers, call centers, cell sites and telephone central offices.
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On 24 August 1970, a criticality incident occurred in the Plutonium Recovery Plant, building B.203. The plant recovered plutonium from miscellaneous sources and was considered tightly controlled. Plutonium was dissolved and transferred into a solvent extraction column through a transfer vessel and backflow trap. Unexpectedly, 2.15 kilograms of plutonium had accumulated the transfer vessel and backflow trap and become just sub-critical.
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A consortium of AECL and Ansaldo Nucleare of Italy, along with the Nuclearelectrica (SNN) SA, Romania’s nuclear public utility, was contracted in 2003 to manage the construction of the partially completed Unit 2 power plant and to commission it into service. Four years later, Unit 2, another CANDU 6-reactor, achieved criticality on 6 May 2007Cernavoda 2 achieves initial criticality and was connected to the national grid on 7 August. It began operating at full capacity on 12 September 2007,Hotnews.ro, Reactorul 2 de la Cernavoda a ajuns la capacitate maxima ("The second unit at the Cernavodă Nuclear Power Plant reached at full capacity ") , September 12, 2007 also producing 706 MW. Unit 2 was officially commissioned on Friday, October 5, 2007 during ceremonies attended by Romanian Prime Minister Călin Popescu-Tăriceanu and senior officials from Atomic Energy of Canada Limited (AECL).
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Intuitively, one may think that the larger the weight for a criterion is, the more critical that criterion should be. However, this may not be the case. It is important to distinguish here the notion of criticality with that of importance. By critical, we mean that a criterion with small change (as a percentage) in its weight, may cause a significant change of the final solution.
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Tungsten carbide is also an effective neutron reflector and as such was used during early investigations into nuclear chain reactions, particularly for weapons. A criticality accident occurred at Los Alamos National Laboratory on 21 August 1945 when Harry Daghlian accidentally dropped a tungsten carbide brick onto a plutonium sphere, known as the demon core, causing the subcritical mass to go supercritical with the reflected neutrons.
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It started commercial operation from 31 December 2014. The second unit achieved criticality on 10 July 2016 and was connected to the grid in August. Commercial operation started on 15 October 2016. The Kerala State Electricity Board (KSEB) board members have approved signing of a power purchase agreement (PPA) with the Nuclear Power Corporation of India (NPCIL) for sourcing electricity from the Kudankulam nuclear power project (KKNPP).
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From 1945 through 1953 Vannikov was Head of the 1st Main Directorate of the Council of People's Commissars of the USSR. In this position Vannikov worked under direct leadership of Lavrenty Beria overseeing the Soviet atomic bomb project. He inadvertently helped the nuclear scientists Yulii Khariton and Igor Kurchatov by walking close to their test reactor. His body fat reflected enough neutrons to approach criticality.
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The buffer tank containing the combined ingredients is specially designed to prevent fission activity from reaching criticality. In a precipitation tank, ammonia is added forming a solid product. This tank is meant to capture any remaining nuclear waste contaminants. In the final process, uranium oxide is placed in the dissolving tanks until purified, without enriching the isotopes, in a wet-process technology specialized by Japan.
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A ring of electrorefined plutonium. It has a purity of 99.96%, weighs 5.3 kg, and is about 11 cm in diameter. It is enough plutonium for one bomb core. The ring shape helps with criticality safety. Only microscopic quantities of plutonium were available until the X-10 Graphite Reactor at the Clinton Engineer Works came online on 4 November 1943, but there were already some worrying signs.
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Integrated modular avionics (IMA) are real-time computer network airborne systems. This network consists of a number of computing modules capable of supporting numerous applications of differing criticality levels. In opposition to traditional federated architectures, the IMA concept proposes an integrated architecture with application software portable across an assembly of common hardware modules. An IMA architecture imposes multiple requirements on the underlying operating system.
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The nuclear reactors of K-27 were troublesome from their first criticality, but the K-27 was able to engage in test operations for about five years. On 24 May 1968, the power output of one of her reactors suddenly dropped sharply; radioactive gases were released into her engine room; and the radiation levels throughout K-27 increased dangerously – by 1.5 grays per hour.
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ZED-2 (Zero Energy Deuterium) is a zero-power nuclear research reactor built at the Chalk River Laboratories in Ontario, Canada. It is the successor to the ZEEP reactor. Designed by AECL for CANDU reactor support, the unit saw first criticality on 7 September 1960. The reactor is still operating at Chalk River where it is used for reactor physics and nuclear fuel research.
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The station's four tall cooling towers are local landmarks. They were manufactured in 96 concrete sections each. By March 2009 the containment structure of the new Kalinin Unit 4 reactor was nearly complete.Second layer of the reactor containment of the 4th unit of Kalinin NPP mounted, 13 March 2009, access date: 3 May 2009 The reactor achieved its first criticality on 8 November 2011.
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The Fukui Prefecture governor, Issei Nishikawa asked the METI for additional stimulus to the prefecture including an expansion of the Shinkansen in turn for the restart of the plant. Monju achieved criticality on May 8, at 10:36 AM JST. Test runs were to continue until 2013, at which point the reactor could have started to feed power into the electric grid, beginning "full fledged" operation.
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Intelligence collection caspabilities were considered early in the planning process, not as an afterthought. The criticality of space systems was such that intelligence needed to determine the threat to them, and then develop alternatives (e.g., UAVs) if the space-based systems are disabled. These space-based systems are not limited to pure intelligence; consider the dependence of both fighting and intelligence functions on GPS.
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The reactor containment structure The Commissariat à l'énergie atomique began construction of this experimental reactor moderated with heavy water and cooled with carbon dioxide (HWGCR) in 1962. The reactor had a planned output power of 70 MWe. The plant achieved criticality in December, 1966. In 1971, however, the French government elected to use pressurized water reactor technology developed in the United States as their model design.
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Riots at anti-nuclear demonstrations near Gorleben, Lower Saxony, Germany, 8 May 1996. Several advanced reactor designs in Germany were unsuccessful. Two fast breeder reactors were built, but both were closed in 1991 without the larger ever having achieved criticality. The High Temperature Reactor THTR-300 at Hamm-Uentrop, under construction since 1970, was started in 1983, but was shut down in September 1989.
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President Eisenhower remotely initiated the first scoop of dirt at the ceremony. The reactor achieved first criticality at 4:30 AM on December 2, 1957. Sixteen days later, on December 18, the first electrical power was generated and full power was achieved on December 23, 1957, although the station remained in test mode. Eisenhower opened the Shippingport Atomic Power Station on May 26, 1958.
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Some these parameters are not independent from one another, for example, changing mass will result in a change of volume among others. Mass: The probability of fission increases as the total number of fissile nuclei increases. The relationship is not linear. If a fissile body has a given size and shape but varying density and mass, there is a threshold below which criticality can not occur.
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Such quantities are called self-averaging. Away from criticality, when the larger lattice is built from smaller blocks, then due to the additivity property of an extensive quantity, the central limit theorem guarantees that RX ~ N−1 thereby ensuring self-averaging. On the other hand, at the critical point, the question whether X is self-averaging or not becomes nontrivial, due to long range correlations.
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Atucha II was "pre-started" on September 28, 2011 by President Cristina Fernández de Kirchner and it was scheduled to start commercial service by mid-2013. By April 2014, it was, however, not yet connected to the grid. On June 3, 2014 reached its first criticality,Pusieron en marcha el reactor de la Central Nuclear Atucha IIPower Output and on June 27, 2014 began to produce energy.
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A re-creation of the 1946 experiment. The half-sphere is seen, but the core inside is not. The beryllium hemisphere is held up with a screwdriver. On May 21, 1946, physicist Louis Slotin and seven other Los Alamos personnel were in a Los Alamos laboratory conducting another experiment to verify the closeness of the core to criticality by the positioning of neutron reflectors.
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After the discoveries of fission, moderation and of the theoretical possibility of a nuclear chain reaction, early experimental results rapidly showed that natural uranium could only undergo a sustained chain reaction using graphite or heavy water as a moderator. While the world's first reactors (CP-1, X10 etc.) were successfully reaching criticality, uranium enrichment began to develop from theoretical concept to practical applications in order to meet the goal of the Manhattan Project, to build a nuclear explosive. In May 1944, the first grams of enriched uranium ever produced reached criticality in the low power (LOPO) reactor at Los Alamos, which was used to estimate the critical mass of U235 to produce the atomic bomb. LOPO cannot be considered as the first light-water reactor because its fuel was not a solid uranium compound cladded with corrosion-resistant material, but was composed of uranyl sulfate salt dissolved in water.
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No amount of 238U can be made "critical" since it will tend to parasitically absorb more neutrons than it releases by the fission process. 235U, on the other hand, can support a self-sustained chain reaction, but due to the low natural abundance of 235U, natural uranium cannot achieve criticality by itself. The trick to achieving criticality using only natural or low enriched uranium, for which there is no "bare" critical mass, is to slow down the emitted neutrons (without absorbing them) to the point where enough of them may cause further nuclear fission in the small amount of 235U which is available. (238U which is the bulk of natural uranium is also fissionable with fast neutrons.) This requires the use of a neutron moderator, which absorbs virtually all of the neutrons' kinetic energy, slowing them down to the point that they reach thermal equilibrium with surrounding material.
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Gabrielle then opens the box, which emits a blinding light. The highly unstable radionuclide material inside reaches explosive criticality as it becomes fully exposed, and Gabrielle bursts into flames, with the room and eventually the entire house becoming engulfed. Hammer, wounded, struggles to his feet, then searches for Velda. Together, the pair flee the flaming room and house, helping each other along the beach, away from the house, to the ocean.
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By mid- afternoon the plant workers and surrounding residents were asked to evacuate. Five hours after the start of the criticality, evacuation commenced of some 161 people from 39 households within a 350-meter radius from the conversion building. Twelve hours after the incident, 300,000 surrounding residents of the nuclear facility were told to stay indoors and cease all agricultural production. This restriction was lifted the following afternoon.
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The Lab had instituted a voluntary buyout plan but could not attain the desired staff reduction. It developed a matrix to rank employees based on three factors: performance, flexibility and criticality of their jobs, and added points for years of service. All of the dismissed employees were at least 40 years old. Twenty-eight of those dismissed sued in January 1997 under the Age Discrimination in Employment Act.
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Andrew John Schofield (better known as Andy Schofield) is an academic and administrator who is the Vice-Chancellor of Lancaster University. A theoretical physicist, he was previously a Pro-Vice-Chancellor at the University of Birmingham and Head of its College of Engineering and Physical Sciences. As an academic, his research focus is in the theory of correlated quantum systems, in particular non-Fermi liquids, quantum criticality and high-temperature superconductivity.
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RAC CRTA-FMECA and MIL-HDBK-338 both identify Risk Priority Number (RPN) calculation as an alternate method to criticality analysis. The RPN is a result of a multiplication of detectability (D) x severity (S) x occurrence (O). With each on a scale from 1 to 10, the highest RPN is 10x10x10 = 1000. This means that this failure is not detectable by inspection, very severe and the occurrence is almost sure.
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The Ghana Research Reactor-1 (GHARR-1) is a nuclear research reactor located in Accra, Ghana and is the only nuclear reactor in the country. It is operated by the National Nuclear Research Institute, a sub-division of the Ghana Atomic Energy Commission. The reactor is a commercial version of the Chinese Miniature Neutron Source Reactor (MNSR) design. The reactor had its first criticality on December 17, 1994.
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A thin hollow shell can have more than the bare-sphere critical mass, as can a cylinder, which can be arbitrarily long without ever reaching criticality. A tamper is an optional layer of dense material surrounding the fissile material. Due to its inertia it delays the expansion of the reacting material, increasing the efficiency of the weapon. Often the same layer serves both as tamper and as neutron reflector.
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Due to the shortage of plutonium-238, a new kind of RTG assisted by subcritical reactions has been proposed. In this kind of RTG, the alpha decay from the radioisotope is also used in alpha-neutron reactions with a suitable element such as beryllium. This way a long-lived neutron source is produced. Because the system is working with a criticality close to but less than 1, i.e.
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Due to increased demand in the 1970s on nuclear research and radioisotopes in the country, the installation of a second nuclear research reactor with higher capacity was projected for the production of radioisotopes only. The reactor with an output capacity of 5 MW, called TR-2, went into service in the same building and the existing pool after becoming criticality in December 1981. The reactor started radioisotope production in 1984.
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There is not enough U-235 in natural uranium to reach criticality. Commercial light-water nuclear reactors, the most prevalent power reactors in the world, use nuclear fuel containing uranium enriched to 3 to 5% U-235 while the leftover is U-238. Each fusion event in the D-T fusion reactor gives off an alpha particle and a fast neutron with around 14 MeV of kinetic energy.
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Russia advanced a credit of 6,416 crore (US$0.97 billion) for both the units. Unit 2 attained criticality on 10 July 2016 and was synchronised with the electricity grid on 29 August. In 2015, Nuclear Power Corporation Ltd (NPCIL) announced a price of 4.29/kW·h (6.4 ¢/kW·h) for energy delivered from Kudankulam nuclear power plant. The ground-breaking ceremony for construction of units 3 & 4 was performed on 17 February 2016.
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For all but the simplest of velocity profiles U, numerical or asymptotic methods are required to calculate solutions. Some typical flow profiles are discussed below. In general, the spectrum of the equation is discrete and infinite for a bounded flow, while for unbounded flows (such as boundary-layer flow), the spectrum contains both continuous and discrete parts. The spectrum of the Orr–Sommerfeld operator for Poiseuille flow at criticality.
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According to a 2012 Government Accountability Office report, several technical challenges remained, including how to keep radioactive waste from incurring a criticality accident and exploding before it was vitrified. As of 2017, the project was undergoing "ongoing" reviews by the Government Accounting Office, Office of Inspector General, Defense Nuclear Facilities Safety Board and other agencies, with a re-baselined projected cost of $16.813 billion and completion date in 2023.
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The results showed that, with a lightly enriched uranium, criticality could be reached. This experiment was the first practical step toward the light-water reactor. After World War II and with the availability of enriched uranium, new reactor concepts became feasible. In 1946, Eugene Wigner and Alvin Weinberg proposed and developed the concept of a reactor using enriched uranium as a fuel, and light water as a moderator and coolant.
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A re-creation of the 1945 criticality accident using the Demon core: a plutonium pit is surrounded by blocks of neutron-reflective tungsten carbide. The original experiment was designed to measure the radiation produced when an extra block was added. The mass went supercritical when the block was placed improperly by being dropped. A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction.
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Geophysical sensors have a long history in conventional military and commercial applications, from weather prediction for sailing, to fish finding for commercial fisheries, to nuclear test ban verification. New challenges, however, keep emerging. For first-world military forces opposing other conventional militaries, there is an assumption that if a target can be located, it can be destroyed. As a result, concealment and deception have taken on new criticality.
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Since the assembly was nearly in the critical state, the accidental addition of that brick caused the reaction to go immediately into the prompt critical region of neutronic behavior. This resulted in a criticality accident. Daghlian reacted immediately after dropping the brick and attempted to knock the brick off the assembly without success. He was forced to disassemble part of the tungsten-carbide pile in order to halt the reaction.
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In a model of an electric transmission network, Heiko Hoffmann and David W. Payton demonstrated that either randomly upgrading lines (sort of like preventive maintenance) or upgrading broken lines to a random breakage threshold suppresses self-organized criticality. Apparently, these strategies undermine the self-organization of large critical clusters. Here, a critical cluster is a collection of transmission lines that are near the failure threshold and that collapse entirely if triggered.
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Les Figues Press is an American non-profit literary press that publishes poetry, prose, visual art, conceptual writing, and translation. Based in Los Angeles, California, the press curates and hosts literary events, readings, performances, and art salons. Les Figues upholds a feminist criticality and editorial vision. Their stated mission is to create aesthetic conversations between readers, writers, and artists by publishing innovative/experimental and avant-garde styled work.
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LOPO served the purposes for which it had been intended: determination of the critical mass of a simple fuel configuration and testing of a new reactor concept. LOPO achieved criticality, in May 1944 after one final addition of enriched uranium. Enrico Fermi himself was at the controls. LOPO was dismantled to make way for a second Water Boiler that could be operated at power levels up to 5.5 kilowatts.
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Experimenters produced bursts of gamma rays and neutrons by assembling Godiva I's three parts and dropping a burst rod through the center. This image shows it in the safe, scrammed, state. The Lady Godiva device was an unshielded, pulsed nuclear reactor originally situated at the Los Alamos National Laboratory (LANL), near Santa Fe, New Mexico. It was one of a number of criticality devices within Technical Area 18 (TA-18).
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These theorems would indicate that certain types of Tweedie models should have a role as equilibrium distributions in natural systems. They can be used to explain the origin of Taylor's law as well as 1/f noise and multifractality. Consequent to Jørgensen's work the Tweedie distributions and their convergence theorem have provided mechanistic insight into complicated natural systems that manifest features of self-organized criticality and random fractals.
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This is used to understand depletion rates of materials consumed as a by-product to extraction. Quoting Graedel et al., "One should not regard the result as how long it will be until we run out, but rather as a useful relative indicator of the contemporary balance between supply and demand for the metal in question." In practice, geological, technological, economic, political and other aspects of criticality are interconnected.
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The social and regulatory components of a materials supply risk can impede or expedite the development of mineral resources. Regulations can hinder the reliability of mineral resource supply. Social perceptions towards the negative environmental and socioeconomic effects on communities typically fuel these regulations. Material criticality employs the policy potential index (PPI) and human development index (HDI) indicators to quantify the social and regulatory components of supply risk evaluation.
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As a not for profit organisation, the gallery serves the local and national art community as a venue for exhibiting alternative and non- commercial art work that offers an environment of criticality, support and learning to emerging and experimental artists.Dell, April (11 July 2010). “Blue Oyster Art Project Space”. Critic. Retrieved 9 June 2016. The space opened in 1999 after the project spaces Honeymoon Suite and Everything Incorporated closed down.
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A half life is the time it takes half of the radiation of a specific substance to decay. A large amount of short-lived isotopes such as 97Zr are present in bomb fallout. This isotope and other short-lived isotopes are constantly generated in a power reactor, but because the criticality occurs over a long length of time, the majority of these short lived isotopes decay before they can be released.
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Imry and Wortis showed that quenched disorder can broaden a first-order transition. That is, the transformation is completed over a finite range of temperatures, but phenomena like supercooling and superheating survive and hysteresis is observed on thermal cycling. Second-order phase transitions are also called "continuous phase transitions". They are characterized by a divergent susceptibility, an infinite correlation length, and a power law decay of correlations near criticality.
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Note that moderation comes from collisions; therefore most moderators are also good reflectors. Enrichment: The probability of a neutron reacting with a fissile nucleus is influenced by the relative numbers of fissile and non-fissile nuclei in a system. The process of increasing the relative number of fissile nuclei in a system is called enrichment. Typically, low enrichment means less likelihood of a criticality and high enrichment means a greater likelihood.
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This equation's factors are roughly in order of potential occurrence for a fission born neutron during critical operation. As already mentioned before, k = (Neutrons produced in one generation)/(Neutrons produced in the previous generation). In other words, when the reactor is critical, k = 1; when the reactor is subcritical, k < 1; and when the reactor is supercritical, k > 1. Reactivity is an expression of the departure from criticality.
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Moreover, several optimization problems arising for instance in job scheduling, location analysis, transportation networks, decision making and discrete event dynamical systems can be formulated and solved in the framework of tropical geometry. A tropical counterpart of the Abel–Jacobi map can be applied to a crystal design. The weights in a weighted finite-state transducer are often required to be a tropical semiring. Tropical geometry can show self-organized criticality.
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The Rogers Commission offered nine recommendations on improving safety in the space shuttle program, and NASA was directed by President Reagan to report back within thirty days as to how it planned to implement those recommendations. This is a summary of the chapter of Recommendations:chapter of Recommendations 1. Design and Independent Oversight 2. Shuttle Management Structure, Astronauts in Management and Shuttle Safety Panel 3. Criticality Review and Hazard Analysis 4.
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However, commissioning dates were put back six months in February 2017, with commercial operation expected in the second half of 2017 and the first half of 2018. In December 2017, Hong Kong media reported that a component had cracked during testing, needing to be replaced. In January 2018 commissioning was rescheduled again, with commercial operation expected in 2018 and 2019. In June 2018, Taishan 1 achieved criticality for the first time.
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The identity element of the sandpile group of a rectangular grid. Yellow pixels correspond to vertices carrying three particles, lilac to two particles, green to one, and black to zero. The Abelian sandpile model, also known as the Bak–Tang–Wiesenfeld model, was the first discovered example of a dynamical system displaying self-organized criticality. It was introduced by Per Bak, Chao Tang and Kurt Wiesenfeld in a 1987 paper.
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Sachdev predicted density wave order and 'magnetic' quantum criticality in tilted lattices of ultracold atoms. This was subsequently observed in experiments. The modeling of tilted lattices inspired a more general model of interacting bosons in which a coherent external source can create and annihilate bosons on each site. This model exhibits density waves of multiple periods, along with gapless incommensurate phases, and has been realized in experiments on trapped Rydberg atoms.
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A deal was signed on 21 July 1960, creating the Whiteshell Nuclear Research Establishment (WNRE). The site was selected to host the Organic-Cooled Deuterium-Reactor Experiment (OCDRE), which later became known as WR-1. The design needed to be ready for construction to start in April 1962. General Electric Canada built the reactor over a period of three years ending in June 1965, and the reactor achieved criticality on 1 November 1965. The idea of an oil-cooled version of the CANDU was eventually abandoned in 1972, and from then on the WR-1 was operated at low power settings in a purely experimental program. Whiteshell led the development of the SLOWPOKE reactor, starting in 1967. However, the first example, SLOWPOKE-1, was built at Chalk River and reached criticality in 1970. Over the next decade, several SLOWPOKE-2 reactors were sold around the world. A larger version, SLOWPOKE-3, was designed to supply 10,000 kW of hot water for district heating.
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At a nonzero temperature phase transition, the fluctuations that develop at a critical point are governed by classical physics, because the characteristic energy of quantum fluctuations is always smaller than the characteristic Boltzmann thermal energy k_B T. At a quantum critical point, the critical fluctuations are quantum mechanical in nature, exhibiting scale invariance in both space and in time. Unlike classical critical points, where the critical fluctuations are limited to a narrow region around the phase transition, the influence of a quantum critical point is felt over a wide range of temperatures above the quantum critical point, so the effect of quantum criticality is felt without ever reaching absolute zero. Quantum criticality was first observed in ferroelectrics, in which the ferroelectric transition temperature is suppressed to zero. A wide variety of metallic ferromagnets and antiferromagnets have been observed to develop quantum critical behavior when their magnetic transition temperature is driven to zero through the application of pressure, chemical doping or magnetic fields.
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On 19 April 2016, unit 3 received from NRA the final approval to restarting. On 27 June, Shikoku Electric completed loading 157 fuel assemblies, of which 16 uranium-plutonium mixed oxide (MOX). Unit 3 achieved criticality on 13 August and resumed commercial service on 7 September. However, on 13 December 2017 the Hiroshima High Court revoked the lower court decision, ordering the close of the unit until the end of September 2018.
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Minnema, "Criticality Accidents and the Blue Glow", American Nuclear Society Winter Meeting, 2007. However, this explanation has not been confirmed and may be inconsistent with the intensity of light reported by witnesses compared to the intensity of heat perceived. Further research is hindered by the small amount of data available from the few instances where humans have witnessed these incidents and survived long enough to provide a detailed account of their experiences and observations.
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The international study, which examined young people's ideas before confirmation school in 2008 and then confirmed in the church in 2013, it became clear that young Finns criticality of the church and religious traditions has increased significantly. In 2013, responding to follow-up will continue. The funeral of an irreligious person traditionally includes music, saattopuhe and floral tributes. Irreligious funerals differ in that religious features such as crosses, hymns and religious speeches are gone.
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FMECA usually feeds into both Maintainability Analysis and Logistics Support Analysis, which both require data from the FMECA. FMECA is the most popular tool for failure and criticality analysis of systems for performance enhancement. In the present era of Industry 4.0, the industries are implementing a predictive maintenance strategy for their mechanical systems. The FMECA is widely used for the failure mode identification and prioritization of mechanical systems and their subsystems for predictive maintenance.
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Tokaimura Nuclear Plant The Tōkai Nuclear Power Plant located in Tokai, Ibaraki Prefecture, Japan was founded in 1966. It served as a fuel conversion company and producer of nuclear reactor fuel rods until 1999. The second accident occurred on 30 September 1999 in a JCO plant and was classified a serious criticality accident.IAEA. (1999). Report on the preliminary fact finding mission following the accident at the nuclear fuel processing facility in Tokaimura, Japan (1st ed.
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At high pressure CeRhIn5 becomes superconducting with a maximum Tc slightly above 2 K at a pressure around 2 GPa, and at the same pressure the Fermi surface of CeRhIn5 changes suggesting so-called local quantum criticality. Also the compound PuCoGa5, which is a superconductor with Tc approximately 18.5 K and which can be considered an intermediate between heavy-fermion and cuprate superconductors, has the same crystal structure.J. L. Sarrao et al.
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Uranium is converted to UO3 powder while the plutonium is converted to PuO2 powder and sent to storage. Pulsed columns were chosen to avoid the risk of a criticality incident occurring within the plant. This can happen if sufficient fissile material comes together to start an uncontrolled chain reaction, producing a large release of neutrons. The risks and mechanisms are well understood and the plant design is arranged to prevent its occurrence, i.e.
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Daghlian was estimated to have received a dose of 510 rem (5.1 Sv) of neutron radiation, from a yield of 1016 fissions. Despite intensive medical care, he developed symptoms of severe radiation poisoning, and his mother and sister were flown out to care for him (his father had died in 1943). He fell into a coma and died 25 days after the accident. He was the first known fatality caused by a criticality accident.
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Carlson developed the HOT mechanism in the early 2000s, and has since applied it to complex systems including the immune system, earthquakes, wildfires and neuroscience. HOT represents a unifying framework that can couple with external environments, which differs from self-organized criticality and the edge of chaos. Carlson has used computational systems biology to understand the immune system. She studies how the immune system changes with age, as well as automimmune disease and homeostasis.
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Like thermal reactors, fast- neutron reactors are controlled by keeping the criticality of the reactor reliant on delayed neutrons, with gross control from neutron-absorbing control rods or blades. They cannot, however, rely on changes to their moderators because there is no moderator. So Doppler broadening in the moderator, which affects thermal neutrons, does not work, nor does a negative void coefficient of the moderator. Both techniques are common in ordinary light-water reactors.
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At 11 p.m. on 16 June 1958 a criticality accident occurred in the C-1 Wing of Building 9212 at the facility, then operating under the management of Union Carbide. In the incident, a solution of highly enriched uranium was mistakenly diverted into a steel drum, causing a fission reaction of 15–20 minutes duration. Eight workers were hospitalized for moderate to severe radiation sickness or exposure, but all eventually returned to work.
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He visited the Metallurgical Laboratory for the first time on 5 October. Between 15 September and 15 November 1942, groups under Herbert Anderson and Walter Zinn constructed 16 experimental piles under the Stagg Field stands. Fermi designed a new pile, which would be spherical to maximize k, which was predicted to be around 1.04, thereby achieving criticality. Leona Woods was detailed to build boron trifluoride neutron detectors as soon as she completed her doctoral thesis.
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It achieved criticality in 1974 and began supplying National Grid power in January 1975. There were many delays and reliability problems before reaching full power. It had three cooling circuits. Leaks in the sodium water steam generators shutdown one and then two of the cooling circuits in 1974 and 1975. By August 1976 it had reached 500 MWt (to produce about 166 MWe) and in 1985 it first reached its design output of 250 MWe.
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In addition to the iron arsenides, the 122 crystal structure plays an important role for other material systems as well. Three famous examples from the field of heavy fermions are CeCu2Si2 (the "first unconventional superconductor" discovered 1978), URu2Si2 (which is also a heavy fermion superconductor but is the focus of active present research due to the so-called "hidden-order phase" below 17.5 K), and YbRh2Si2 (one of the prime examples of quantum criticality).
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Phillips, J. C. Proc. Natl. Acad. Sci. 107,1307 (2010) Next he found a wayPhillips, J. C. Phys. Rev. E 80, 051916 (2009) to connect Per Bak’s ideas of Self-Organized Criticality to proteins, which are networks compacted into globules by hydropathic forces, by using a new hydrophobicity scale (similar in precision to his dielectric scale of ionicity) invented in Brazil using bioinformatic methods on more than 5000 structures in the Protein Data Base.
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Albert Wattenberg (April 13, 1917 – June 27, 2007), was an American experimental physicist. During World War II, he was with the Manhattan Project's Metallurgical Laboratory at the University of Chicago. He was a member of the team that built Chicago Pile-1, the world's first artificial nuclear reactor, and was one of those present on December 2, 1942, when it achieved criticality. In July 1945, he was one of the signatories of the Szilard petition.
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These requirements are generally specified in the contract statement of work and depend on how much leeway the customer wishes to provide to the contractor. Reliability tasks include various analyses, planning, and failure reporting. Task selection depends on the criticality of the system as well as cost. A safety-critical system may require a formal failure reporting and review process throughout development, whereas a non-critical system may rely on final test reports.
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A common practice is to apply a double contingency analysis to the operation in which two or more independent, concurrent and unlikely changes in process conditions must occur before a nuclear criticality accident can occur. For example, the first change in conditions may be complete or partial flooding and the second change a re-arrangement of the fissile material. Controls (requirements) on process parameters (e.g., fissile material mass, equipment) result from this analysis.
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INRNE also owns an IRT-2000 research reactor that achieved first criticality in 1961, but has been shut down in 1999 and awaiting reconstruction since then. Until 1992, when the government of Filip Dimitrov ordered an end to uranium mining, Bulgaria was extracting 645 tonnes of uranium annually, and produced yellowcake. The material was shipped to the USSR for processing, and then returned to Bulgaria as fuel for the Kozloduy power plant.
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This was replaced by a stainless steel cladding, but this absorbed enough neutrons to affect criticality, and in turn required the design to operate on slightly enriched uranium rather than the Magnox's natural uranium, driving up fuel costs. Ultimately the economics of the system proved little better than Magnox. Former Treasury Economic Advisor, David Henderson, described the AGR programme as one of the two most costly British government-sponsored project errors, alongside Concorde.
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Construction took place between 1974 and 1981, which cost around 2.5 billion DM. The reactor, a German third-generation pressurized water reactor with an electrical net power output of 1,345 megawatts, achieved first criticality on December 9, 1981. The plant is managed by PreussenElektra GmbH. The two tall cooling towers are visible from far away. As with almost all other nuclear plants, temporary storage facilities for spent nuclear fuel are present on site.
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RCM can be used to create a cost-effective maintenance strategy to address dominant causes of equipment failure. It is a systematic approach to defining a routine maintenance program composed of cost-effective tasks that preserve important functions. The important functions (of a piece of equipment) to preserve with routine maintenance are identified, their dominant failure modes and causes determined and the consequences of failure ascertained. Levels of criticality are assigned to the consequences of failure.
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Miltenberger et al.Miltenberger, P., D. Sornette and C.Vanneste, Fault self-organization as optimal random paths selected by critical spatio-temporal dynamics of earthquakes, Phys.Rev.Lett. 71, 3604-3607 (1993) and Sornette et al. (1994) Sornette, D., P. Miltenberger and C. Vanneste, Statistical physics of fault patterns self-organized by repeated earthquakes, Pure and Applied Geophysics 142, N. 3/4, 491-527 (1994) showed that self-organized criticality in earthquakes and tectonic deformations are related to synchronization of threshold relaxation oscillators.
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Operation Crossroads Test Able, a 23-kiloton air-deployed nuclear weapon detonated on July 1, 1946. This bomb used, and consumed, the infamous Demon core that took the lives of two scientists in two separate criticality accidents. Mushroom-shaped cloud and water column from the underwater nuclear explosion of July 25, 1946, which was part of Operation Crossroads. November 1951 nuclear test at the Nevada Test Site, from Operation Buster, with a yield of 21 kilotons.
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Critical manifolds of dimension d > 1 and d > 2 may have physically reachable borders of dimension d-1 which in turn may have borders of dimension d-2. The system still is critical at these borders. However, criticality terminates for good reason, and the points on the borders normally belong to another universality class than the universality class realized within the critical manifold. All the points on the border of a critical manifold are multicritical points.
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Because of the importance of adaptation in many natural systems, adaptation to the edge of the chaos takes a prominent position in many scientific researches. Physicists demonstrated that adaptation to state at the boundary of chaos and order occurs in population of cellular automata rules which optimize the performance evolving with a genetic algorithm. Another example of this phenomenon is the self-organized criticality in avalanche and earthquake models. The simplest model for chaotic dynamics is the logistic map.
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The core was compressed to prompt super-criticality by the implosion generated by the high explosive lens. This design became known as a "Christy Core" or "Christy pit" after physicist Robert F. Christy, who made the solid pit design a reality after it was initially proposed by Edward Teller. Along with the pit, the whole physics package was also informally nicknamed "Christy['s] Gadget". Of the several allotropes of plutonium, the metallurgists preferred the malleable δ (delta) phase.
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The new design was called Little Boy. A Little Boy unit on Tinian connected to test equipment, possibly to test or charge components within the device After repeated slippages, the first shipment of slightly enriched uranium (13 to 15 percent uranium-235) arrived from Oak Ridge in March 1944. Shipments of highly enriched uranium commenced in June 1944. Criticality experiments and the Water Boiler had priority, so the metallurgists did not receive any until August 1944.
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Sufficient enriched uranium had arrived by May to start it up, and it went critical on 9 May 1944. It was only the third reactor in the world to do so, the first two being the Chicago Pile-1 reactor at the Metallurgical Laboratory and the X-10 Graphite Reactor at the Clinton Engineer Works. Improved cross-section measurements allowed Christy to refine his criticality estimate to 575 grams. In fact, only 565 grams were required.
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It achieved criticality on 1 November 1965 and full power in December 1965. An effort to commercialized the design began in 1971 but ended in 1973 when the heavy water cooled units became the standard. From then on WR-1 operated at reduced power limits for irradiation experiments and heating the WNRE site. WR-1 was shut down for the last time in 1985, was defuelled, and is undergoing decommissioning scheduled to be completed in 2023.
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The Trojan Powder Company had formerly manufactured gunpowder and dynamite on a site on the banks of the Columbia River, from the town of Rainier, Oregon. In 1967 Portland General Electric chose the site for a new nuclear power plant. Construction began on February 1, 1970; first criticality was achieved on December 15, 1975, and grid connection eight days later on December 23. Commercial operation began on May 20, under a 35-year license to expire in 2011.
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Fermi described the apparatus as "a crude pile of black bricks and wooden timbers". The reactor was assembled in November 1942, by a team that included Fermi, Leo Szilard (who had previously formulated an idea for non-fission chain reaction), Leona Woods, Herbert L. Anderson, Walter Zinn, Martin D. Whitaker, and George Weil. The reactor used natural uranium. This required a very large amount of material in order to reach criticality, along with graphite used as a neutron moderator.
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This was the first reactor of the Nuclear Engineering program at Texas A&M;, built in the 1950s and licensed in August 26, 1957. It is going through system upgrades and is not operational for 2017. The reactor is of a negligible thermal power of 5 watts but achieves criticality, making it a critical assembly. The AGN-201M type reactor is also employed at University of New Mexico and another AGN-201 type is used at Idaho State University.
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To ensure predictability, all aperiodic messages must be included in the bandwidth management calculations. Time Triggered Bus Scheduling ensures adequate flexibility for increasing network traffic during the lifetime of the system if growth potential is planned. As an example, system design will allow nodes to be integrated into the network without affecting the existing nodes. Furthermore, the predictable behavior enforced by Time Triggered Bus Scheduling allows systems with different criticality levels to coexist on the same network.
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The critical point is described by a conformal field theory. According to the renormalization group theory, the defining property of criticality is that the characteristic length scale of the structure of the physical system, also known as the correlation length ξ, becomes infinite. This can happen along critical lines in phase space. This effect is the cause of the critical opalescence that can be observed as a binary fluid mixture approaches its liquid–liquid critical point.
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In order to allow criticality, the fuel must be enriched, increasing the amount of 235U to a usable level. In light-water reactors, the fuel is typically enriched to between 2% and 5% 235U (the leftover fraction with less 235U is called depleted uranium). Enrichment facilities are expensive to build and operate. They are also a proliferation concern, as they can be used to enrich the 235U much further, up to weapons-grade material (90% or more 235U).
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RA-1 Enrico Fermi is a research reactor in Argentina and the first nuclear reactor to be built in that country. Construction started April 1957, with first criticality 17 January 1958. It produced the first medical and industrial radioisotopes made in Argentina, and was used to train staff for the first two nuclear power stations there. It is a pool type, with enriched uranium oxide fuel (20% U-235), light water coolant and moderator, and a graphite reflector.
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The facility houses two indigenously built Pressurised Heavy-Water Reactors (PHWRs), MAPS-1 and MAPS-2 designed to produce 235 MW of electricity each. MAPS-1 was completed in 1981, but start-up was delayed due to a shortage of heavy water. After procuring the necessary heavy water, MAPS-1 went critical in 1983 and began operating at full power on 27 January 1984. MAPS-2 obtained criticality in 1985 and began full power operations on 21 March 1986.
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They are also used for devices where gas and liquid are put in contact for purposes of gas absorption, stripping or chemical reaction, and as a support for biofilms in biological reactors. Raschig rings made from borosilicate glass are sometimes employed in the handling of nuclear materials. They are used inside vessels and tanks containing solutions of fissile material, for example solutions of enriched uranyl nitrate. There they act as neutron absorbers to prevent a criticality accident.
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In 1963, FOA halted criticality experiments, and by July 1972, even theoretical research using its acquired plutonium was shut down. Earlier, primarily due to cost, Sweden opted to use U.S.-designed light water reactors using imported enriched uranium in lieu of heavy water reactors operating on indigenous uranium. Also, the Swedish supreme commander announced that the country abandoned the nuclear option in 1965. Another key event was an electrical problem at the Ågesta that jeopardized the reactor's cooling system.
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There were concerns that a reactor so small might not achieve criticality, so zirconium hydride (a good moderator) was added, and the thickness of the beryllium reflector was increased to . There were nine control drums. The whole reactor, including the aluminum pressure vessel, weighed . Pewee 1 was started up three times: for check out on 15 November 1968, for a short duration test on 21 November, and for a full power endurance test on 4 December.
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India has nuclear power plants operating in the following states: Maharashtra, Gujarat, Rajasthan, Uttar Pradesh, Tamil Nadu and Karnataka. These reactors have an installed electricity generation capacity of between 100 MW and 540 MW each. The Kudankulam nuclear power plant (KNPP) is the single largest nuclear power station in India. KNPP Unit 1 with a capacity of 1,000 MWe was commissioned in July 2013, while Unit 2, also with a capacity of 1,000 MWe, attained criticality in 2016.
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Two additional units are under construction. The plant has suffered multiple shutdowns, leading to calls for an expert panel to investigate. First 700 MW PHWR unit under phase II of Kakrapar Atomic Power Station achieved first criticality in July 2020. In 2011, uranium was discovered in the Tummalapalle uranium mine, the country's largest uranium mine and possibly one of the world's largest. The reserves were estimated at 64,000 tonnes, and could be as large as 150,000 tonnes.
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Thomas TelfordInternational Commission on Large Dams (ICOLD) (2003) Risk Assessment in Dam Safety Management. ICOLD, ParisBritish Standards Institution (BSIA) (1991) BC 5760 Part 5: Reliability of systems equipment and components – Guide to failure modes effects and criticality analysis (FMEA and FMECA). Many engineers use computers to produce and analyze designs, to simulate and test how a machine, structure, or system operates, to generate specifications for parts, to monitor the quality of products, and to control the efficiency of processes.
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For energy production purposes, one might use a container located inside a solenoid. The container is filled with gaseous uranium hexafluoride, where the uranium is enriched, to a level just short of criticality. Afterward, the uranium hexafluoride is compressed by external means, thus initiating a nuclear chain reaction and a great amount of heat, which in turn causes an expansion of the uranium hexafluoride. Since the UF6 is contained within the vessel, it can't escape and thus compresses elsewhere.
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This is however of little use on the surface of a planet, where a NSWR would eject massive quantities of superheated steam, still containing fissioning nuclear salts. Terrestrial testing might be subject to reasonable objections; as one physicist wrote, "Writing the environmental impact statement for such tests [...] might present an interesting problem ...". It is also not certain that fission in a NSWR could be controlled: "Whether fast criticality can be controlled in a rocket engine remains an open question".
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Unit One took 16 years to build, completed in 1996. It produces 705.6 MW2007 News Releases - Second CANDU Unit in European Union Officially In Service of electricity. Unit Two took 27 years to build, achieving initial criticality in 2007Cernavoda 2 achieves initial criticality and produces 706 MW of electricity. Unit Three and Unit Four were expected to be operational by the year 2015 (thirty-five years after the start of construction) and the total electricity production of the units was to be around 1,500 MW. The total cost of the units is expected to be around US$ 6 billion. On 7 March 2008, Nuclearelectrica, ArcelorMittal, CEZ, Electrabel, Enel, Iberdrola and RWE agreed to set up a company dedicated to the completion, commissioning and operation of Units 3 and 4. The company is expected to be registered in May 2008. When four of the five reactors were to be fully functional the Cernavodă Nuclear Power Plant would have produced around 40% of Romania's total electricity needs. In 2002 and 2006, Romania made efforts to complete unit 3 and 4, respectively.
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Reports of 13 observations of neutron beams 1.5 km "southwest of the plant's No. 1 and 2 reactors" from 13 to 16 March raised the possibility that nuclear chain reactions could have occurred after the initial SCRAMing of the reactors at Fukushima Daiichi. 16 March reports that fuel rods in the spent fuel pool at Unit 4 could have been exposed to air appeared to indicate that uncontrolled fission may have occurred in that fuel pool. Later reports of exceptionally high iodine-134 levels appeared to confirm this theory because very high levels of iodine-134 would be indicative of criticality. The same report also showed high measurements of chlorine-38, which some nuclear experts used to calculate that self-propagating fission must be occurring in Unit 1. Despite TEPCO suggesting the iodine-134 report was inaccurate, the IAEA appeared to accept the chlorine-based analysis as a valid theory suggesting criticality when it stated at a press conference that "melted fuel in the No. 1 reactor building may be causing isolated, uncontrolled nuclear chain reactions".
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In a nuclear setting, Cherenkov radiation is instead seen in dense media such as water or in a solution such as uranyl nitrate in a reprocessing plant. Cherenkov radiation could also be responsible for the "blue flash" experienced in an excursion due to the intersection of particles with the vitreous humour within the eyeballs of those in the presence of the criticality. This would also explain the absence of any record of blue light in video surveillance of the more recent incidents.
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The second reactor attained criticality on March 21, 1977 and commercial operation began on July 1. Following a decision in the Riksdag in 1997, the Government of Sweden decided that the first reactor was to close July 1, 1998, and the second July 1, 2001. Due to the operator's appeal of the decision and lack of emission-free replacement, the closure was postponed. The demolition of the facility will await the construction of a storage facility, scheduled to be ready in the 2020s.
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Stricken from the Naval Vessel Register on 31 July 1989, she arrived at the Naval Nuclear Prototype Training Unit at Goose Creek, South Carolina, in August 1989 after achieving initial criticality in her new role on 29 July 1989. Her modifications included special mooring arrangements, including Water Brake, a mechanism to absorb power generated by her main propulsion shaft. She is scheduled to operate as a moored training ship until 2020 while undergoing shipyard availabilities for repairs and alterations at five-year intervals.
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If the fuel assemblies would fall, this could lead to re- criticality. In the meantime preparative works began to install a recirculation cooling system at the fuel pool, that should be operational in the first weeks of July. On 14 July, TEPCO began injecting nitrogen into the containment vessel, which was expected to reduce the likelihood of further hydrogen explosions. On 1 July, the spent fuel pool was switched from the water-injection cooling system to a circulatory cooling system.
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Two types of mistakes were deemed most serious: errors committed during field operations, such as maintenance and testing, that can cause an accident; and human errors made during small accidents that cascade to complete failure. In 1946 Canadian Manhattan Project physicist Louis Slotin performed a risky experiment known as "tickling the dragon's tail"Jungk, Robert. Brighter than a Thousand Suns. 1956. p.194 which involved two hemispheres of neutron-reflective beryllium being brought together around a plutonium core to bring it to criticality.
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The use of the low- and high-speed explosives again results in a spherical converging detonation wave to compress the physics package. The original Gadget device used in the Trinity test and Fat Man dropped on Nagasaki used Baratol as the low-VoD explosive and Composition B as the fast, but other combinations can be used. "Trinity" gadget. The alternating high and slow explosives (in purple) are the explosive lens which forces the spherical core to compress into prompt criticality.
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KAPS-2 was shut down after a coolant channel leak in July 2015 and a similar issue forced the shutdown of KAPS-1 in March 2016. After a replacement of coolant channels and feeder tubes, KAPS-2 attained criticality in September 2018. Maintenance on KAPS-1 was completed ahead of schedule and was brought to operation on 19 May 2019. The construction costs were originally estimated to be ₹382.52 crore; the plant was finally finished at a price of ₹1,335 crore.
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Several epidemiological studies and toxicological reports provide evidence of chloroprene's capability to inflict occupational health and safety concerns. However, varying reviews of the degree to which chloroprene should be held responsible for health concerns highlight the criticality of sound scientific research. Nonetheless, health and safety practices should always be implemented in the workplace. Some of these occupational concerns include: cleaning equipment or unclogging pipes coated with chloroprene, inhaling chloroprene off-gas, chloroprene spontaneously reacting with other chemicals and chloroprene inducing a workplace fire.
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Alvin Cushman Graves (November 4, 1909 – July 28, 1965) was an American nuclear physicist who served at the Manhattan Project's Metallurgical Laboratory and the Los Alamos Laboratory during World War II. After the war, he became the head of J (Test) Division at Los Alamos, and was director or assistant director of numerous nuclear weapons tests during the 1940s and 1950s. Graves was badly injured in the 1946 laboratory criticality accident in Los Alamos that killed Louis Slotin, but recovered.
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The result of this is that, when dealing with crises and extremes, power law tails are the "normal" case. The unique property of power laws is that they are scale-invariant, self-similar and fractal. This property implies that all events—both large and small—are generated by the same mechanism, and thus there will be no distinct precursors by which the largest events may be predicted. A well-known conceptual framework for events of this type is self-organized criticality.
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Detonation risks can be reduced by the use of catalytic hydrogen recombiners. Brief re-criticality (resumption of neutron-induced fission) in parts of the corium is a theoretical but remote possibility with commercial reactor fuel, due to low enrichment and the loss of moderator. This condition could be detected by presence of short life fission products long after the meltdown, in amounts that are too high to remain from the pre-meltdown reactor or be due to spontaneous fission of reactor-created actinides.
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This increases the size of the reactor core and the leakage of neutrons. It is also the practical reason for the calandria design, otherwise, a very large pressure vessel would be needed.B. Rouben, "Basic CANDU Design" , University Network for Excellence in Nuclear Engineering, 2005. The low 235U density in natural uranium also implies that less of the fuel will be consumed before the fission rate drops too low to sustain criticality, because the ratio of 235U to fission products + 238U is lower.
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Indeed, after 1943, he built and maintained all the radium and beryllium neutron sources used by the entire Manhattan Project. He assisted in the construction of Chicago Pile-1, the world's first artificial nuclear reactor, and was one of those present on December 2, 1942, when it achieved criticality. Afterwards, Eugene Wigner opened a bottle of Chianti to celebrate, which those present drank from paper cups. The bottle was signed by those present, and kept as a souvenir by Wattenberg.
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Both fixed-source and criticality calculations can be solved using deterministic methods or stochastic methods. In deterministic methods the transport equation (or an approximation of it, such as diffusion theory) is solved as a differential equation. In stochastic methods such as Monte Carlo discrete particle histories are tracked and averaged in a random walk directed by measured interaction probabilities. Deterministic methods usually involve multi-group approaches while Monte Carlo can work with multi-group and continuous energy cross-section libraries.
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This creates efficient, tamper-proof, and non-bypassable virtual machines. Hardware resources are robustly partitioned into almost zero overhead VMs populated with a mix of OSes, RTOSes and bare-metal applications. Mixed criticality safety systems can be constructed that minimize high Design Assurance Levels (DAL) source lines of code (SLOC) counts to reduce certification costs and technical risks of future programs. LynxSecure supports paravirtualized Linux and LynxOS real-time operating systems, as well as full virtualization of the Windows operating system.
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The 3 MW SL-1 was a U.S. Army experimental nuclear power reactor at the National Reactor Testing Station, Idaho National Laboratory. It was derived from the Borax Boiling water reactor (BWR) design and it first achieved operational criticality and connection to the grid in 1958. For reasons unknown, in 1961 a technician removed a control rod about 22 inches farther than the prescribed 4 inches. This resulted in a steam explosion which killed the three crew members and caused a meltdown.
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It has been proposed that some biological systems might lie near critical points. Examples include neural networks in the salamander retina, bird flocks gene expression networks in Drosophila, and protein folding. However, it is not clear whether or not alternative reasons could explain some of the phenomena supporting arguments for criticality. It has also been suggested that biological organisms share two key properties of phase transitions: the change of macroscopic behavior and the coherence of a system at a critical point.
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She has received a DAAD (Deutscher Akademischer Austausch Dienst) grant and a Rhizome commission grant and was shortlisted for the artraker prize. Amin has had teaching positions at the University of Minnesota, American University in Cairo, and the University of Applied Sciences in Berlin. She has given various lectures and workshops worldwide. Her work titled The Earth Is an Imperfect Ellipsoid (2016) was featured in Mizna's Summer'16 Issue, where she was also interviewed in Lana Barkawi's essay "Criticality and Dissent".
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Post-work order quality checks involve one of two methods: 100% audit of all work orders or statistical sampling of randomly selected work orders. Randomly selected work orders should place more stringent statistical controls based on the clinical criticality of the device involved. For example, 100% of items critical to patient treatment but only 50% of ancillary items may be selected for sampling. In an ideal setting, all work orders are checked, but available resources may dictate a less comprehensive approach.
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The molasses tank, date unknown Several factors might have contributed to the disaster. The tank was constructed poorly and tested insufficiently, and carbon dioxide production might have raised the internal pressure due to fermentation in the tank. Warmer weather the previous day would have assisted in building this pressure, as the air temperature rose from over that period. The failure occurred from a manhole cover near the base of the tank, and a fatigue crack there possibly grew to the point of criticality.
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The solution is then simulated by the simulation engine while the trainee exercises monitoring and control throughout the execution. A planned project can be simulated using Monte Carlo simulation. This is done in automatic mode (without a human decision maker involved) and shows the probability to finish the project at any time period or at any cost. Furthermore, based on the Monte Carlo simulation the probability of each activity to be on the critical path is estimated (the criticality index).
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These Gen IV MSR concepts are often more accurately termed an epithermal reactor than a thermal reactor due to the average speed of the neutrons that would cause the fission events within its fuel being faster than thermal neutrons. Fast spectrum MSR concept designs (eg MCSFR) do away with the graphite moderator. They achieve criticality by having a sufficient volume of salt with sufficient fissile material. Being fast spectrum they can consume much more of the fuel and leave only short lived waste.
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In his early career, he worked on problems in statistical physics, dynamical system and complex systems. In 1987, along with Per Bak and Kurt Wiesenfeld, he proposed the concept and developed the theory for self-organized criticality, which had and continues to have broad applications in complex systems with scale invariance. The model they used to illustrate the idea is referred to as the Bak-Tang-Wiesenfeld "sandpile" model. His current research interest is at the interface between physics and biology.
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Conventional fission power plants rely on the chain reaction caused when nuclear fission events release neutrons that cause further fission events. This process is known as a chain reaction. Each fission event in uranium releases two or three neutrons, so by careful arrangement and the use of various absorber materials the system can be balanced such that one of those neutrons causes another fission event while the other one or two are lost. This careful balance is known as criticality.
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Due to the high core temperatures, however, on the return trip the neutrons are up scattered in the fuel region, which leads to a significant negative reactor worth. To achieve criticality, this reactor is operated at very high pressure and the exterior radial wall is made up of a moderator of some sort, generally beryllium oxide. Moderation can also come from introducing moderating particles into either the fuel or propellant streams, but by doing so, the benefits in neutronics is canceled by loss of rocket performance.
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350px For both the Trinity device and the Fat Man, the Nagasaki bomb, nearly identical plutonium fission through implosion designs were used. The Fat Man device specifically used , about in volume, of Pu-239, which is only 41% of bare-sphere critical mass. (See Fat Man article for a detailed drawing.) Surrounded by a U-238 reflector/tamper, the Fat Man's pit was brought close to critical mass by the neutron-reflecting properties of the U-238. During detonation, criticality was achieved by implosion.
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Against operating procedures, the hemispheres were separated only by a screwdriver. The screwdriver slipped and set off a chain reaction criticality accident filling the room with harmful radiation and a flash of blue light (caused by excited, ionized air particles returning to their unexcited states). Slotin reflexively separated the hemispheres in reaction to the heat flash and blue light, preventing further irradiation of several co-workers present in the room. However, Slotin absorbed a lethal dose of the radiation and died nine days later.
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In December 1961, the major construction phase was concluded and system testing was in full swing. Criticality was first attained on April 11, 1962, and first steam of nuclear origin was produced on May 8. The first electrical power was fed to the system on June 4, and on June 28 first full-power generation of 20 MW(e) gross was attained. NPD began operation in 1962 and was operational until 1987, long after vastly more powerful and modern CANDU units came on-line.
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Mismanagement or control rod failure have often been blamed for nuclear accidents, including the SL-1 explosion and the Chernobyl disaster. Homogeneous neutron absorbers have often been used to manage criticality accidents which involve aqueous solutions of fissile metals. In several such accidents, either borax (sodium borate) or a cadmium compound has been added to the system. The cadmium can be added as a metal to nitric acid solutions of fissile material; the corrosion of the cadmium in the acid will then generate cadmium nitrate in situ.
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This resulted in fuel exhaustion to all engines. His > inattention resulted from preoccupation with a landing gear malfunction and > preparations for a possible landing emergency. The NTSB also determined the following contributing factor: > The failure of the other two flight crewmembers either to fully comprehend > the criticality of the fuel state or to successfully communicate their > concern to the captain The fuel situation was known to be on the minds of the pilot and crew to some degree. Transcripts of cockpit recordings confirm this.
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Some spacecraft flight systems such as that of the SpaceX Dragon consider Byzantine fault tolerance in their design. Byzantine fault tolerance mechanisms use components that repeat an incoming message (or just its signature) to other recipients of that incoming message. All these mechanisms make the assumption that the act of repeating a message blocks the propagation of Byzantine symptoms. For systems that have a high degree of safety or security criticality, these assumptions must be proven to be true to an acceptable level of fault coverage.
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Another piece in the puzzle is work on computational complexity, specifically that critical points have been shown to exist in NP-complete problems, where near-optimum solutions are widely dispersed and separated by barriers in the search space causing local search algorithms to get stuck or severely hampered. It was the evolutionary self-organised criticality model by Bak and Sneppen and the observation of critical points in combinatorial optimisation problems that lead to the development of Extremal Optimization by Stefan Boettcher and Allon Percus.
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In the 1990s, researchers at the KEK particle physics laboratory near Tokyo began developing the FFA concept, culminating in a 150 MeV machine in 2003. A non-scaling machine, dubbed PAMELA, to accelerate both protons and carbon nuclei for cancer therapy has been designed. Meanwhile, an ADSR operating at 100 MeV was demonstrated in Japan in March 2009 at the Kyoto University Critical Assembly (KUCA), achieving "sustainable nuclear reactions" with the critical assembly's control rods inserted into the reactor core to damp it below criticality.
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The child was a healthy daughter, Marilyn Edith. Graves was badly injured in the 1946 laboratory criticality accident at Los Alamos that killed Louis Slotin. Slotin, who was training Graves to replace him in his position as chief bomb assembler for Los Alamos, was demonstrating the dangerous "tickling the dragon's tail" test to Graves and several other scientists when the accident occurred. Graves, who was nearest to Slotin, suffered an estimated dose of 390 roentgens, and was given a 50 percent chance of survival.
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A report by Deloitte in Jan 2020, titled Mental health and employers - Refreshing the case for investment detailed a 'deep dive' into Leaveism. It modelled numerous studies conducted over recent years and highlighted the criticality of the phenomena in understanding employees workplace responses to stress and ill-health. The report concluded that younger employees were more susceptible to leaveism and, as such, required more support. The report also made recommendations about what organisations could practically do to reduce the associated risks of Leaveism behaviours.
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Supply risk is one of three dimensions that determine a material's criticality. Supply risk can be evaluated for the medium term (5–10 years, typically most appropriate for corporations and governments) and the long term (multiple decades, usually considered by long- range planners, futurists, and sustainability scholars). Supply risk consists of three components: Geological, Technological, and Economic; Social and Regulatory; Geopolitical. The first component focuses on the availability of the material's supply and the last two focus on how access to that supply could be restricted.
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Antimony has consistently been ranked high in European and US risk lists concerning criticality of the element indicating the relative risk to the supply of chemical elements or element groups required to maintain the current economy and lifestyle. With most of the antimony imported into Europe and the US coming from China, Chinese production is critical to supply. As China is revising and increasing environmental control standards, antimony production is becoming increasingly restricted. Additionally Chinese export quotas for antimony have been decreasing in the past years.
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Upon taking over leadership responsibilities, TEPCO's new president issued a public commitment that the company would take all the countermeasures necessary to prevent fraud and restore the nation's confidence. By the end of 2005, generation at suspended plants had been restarted, with government approval. In 2007, however, the company announced to the public that an internal investigation had revealed a large number of unreported incidents. These included an unexpected unit criticality in 1978 and additional systematic false reporting, which had not been uncovered during the 2002 inquiry.
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The Experimental Breeder Reactor II Experimental Breeder Reactor-II (EBR-II) is a sodium-cooled fast reactor designed, built and operated by Argonne National Laboratory at the National Reactor Testing Station in Idaho.Experimental Breeder Reactor II, Argonne National Laboratory It was shut down in 1994. Custody of the reactor was transferred to Idaho National Laboratory after its founding in 2005. Initial operations began in July 1964 and it achieved criticality in 1965 at a total cost of more than US$32 million (US$ million in 2019 dollars).
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The FME(C)A is a design tool used to systematically analyze postulated component failures and identify the resultant effects on system operations. The analysis is sometimes characterized as consisting of two sub- analyses, the first being the failure modes and effects analysis (FMEA), and the second, the criticality analysis (CA). Successful development of an FMEA requires that the analyst include all significant failure modes for each contributing element or part in the system. FMEAs can be performed at the system, subsystem, assembly, subassembly or part level.
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The Kundu-Ekchaus equation is associated with a Lax pair, higher conserved quantity, exact soliton solution, rogue wave solution etc. Over the years various aspects of this equation, its generalizations and link with other equations have been studied. In particular, relationship of Kundu-Ekchaus equation with the Johnson's hydrodynamic equation near criticality is established, its discretizations, reduction via Lie symmetry, complex structure via Bernoulli subequation, bright and dark soliton solutions via Bäcklund transformation and Darboux transformation with the associated rogue wave solutions, are studied.
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This increased flux and attendant fission rate produces radiation that contains both a neutron and gamma ray component and is extremely dangerous to any unprotected nearby life-form. The rate of change of neutron population depends on the neutron generation time, which is characteristic of the neutron population, the state of "criticality", and the fissile medium. A nuclear fission creates approximately 2.5 neutrons per fission event on average. Hence, to maintain a stable, exactly critical chain reaction, 1.5 neutrons per fission event must either leak from the system or be absorbed without causing further fissions.
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On 15 July 2010, China's first CPR-1000 nuclear power plant, Ling Ao-3, was connected to the grid, having started criticality testing on 11 June 2010. It started commercial operations on 27 September 2010, with Ling Ao-4 starting commercial operation on 7 August 2011. 18 CPR-1000 reactors have been built as of December 2019. Besides Ling Ao unit 3 & 4, the CPR-1000 reactor has been realised in Fangchenggang (unit 1 & 2), Fangjiashan (unit 1 & 2), Hongyanhe (unit 1-4), Ningde (unit 1-4), Yangjiang (unit 1-4).
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Simply piling enough pebbles together in a critical geometry will allow for criticality. The pebbles are held in a vessel, and an inert gas (such as helium, nitrogen or carbon dioxide) circulates through the spaces between the fuel pebbles to carry heat away from the reactor. Pebble-bed reactors need fire-prevention features to keep the graphite of the pebbles from burning in the presence of air if the reactor wall is breached, although the flammability of the pebbles is disputed. Ideally, the heated gas is run directly through a turbine.
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At its peak in 1979, the construction project employed 3,500 workers and 108 individual contracts out of 139, were granted to local businesses. Point Lepreau was licensed for operation on 21 July 1982, achieved criticality four days later and began commercial operations on 1 February 1983. Tense labour relations on the worksite and skyrocketing construction costs, a common trait among large infrastructure projects built in that period, tripled the early forecasts. The estimated price tag of C$466 million in 1974 increased to C$684 two years later and to C$895 in 1978.
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Just because a task is on the Critical Path all of the time, does not always mean that the task is going to be significant to the project completion date. For example, a task that is only 1 day long is unlikely to affect the project finish but it can still have a 100% Criticality Index. To avoid this problem one must also measure the correlation between the duration of a task and the duration of the project. Spearman's Rank correlation or Pearson's Product Moment can be used to measure the correlation.
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Eight years later, a Reserve Communications Officer Indoctrination Course was added to provide instruction to the Fleet Marine Forces Reserve. On 2 February 1954, ground was broken for a new, $300,000 building on the edge of the Potomac in Quantico. After a year- and-a-half of construction, the building was dedicated on 12 December 1955 and named “Edson Hall” in honor of Major General Merritt A. Edson, a World War II Marine hero and leader of the famed “Edson’s Raiders” and a vocal proponent of the criticality of communications in combat.
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Vishwanath has made important contributions to several areas in condensed matter physics. In particular, his most important contributions have been in deconfined quantum criticality (with T. Senthil, Matthew P. A. Fisher, Subir Sachdev and Leon Balents), Dirac and Weyl semimetals, iron-based high-temperature superconductors, magnetic skyrmion phases, and topological insulators where, in particular and more recently, he has explored several aspects and field theories of symmetry protected topological phases and Floquet topological phases. He has also done important works on quantum magnetic systems and quantum entanglement properties of spin liquids and related topological orders.
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The China Experimental Fast Reactor (CEFR) is China's first fast nuclear reactor, and is located outside Beijing at the China Institute of Atomic Energy. It aims to provide China with fast-reactor design, construction, and operational experience, and will be a key facility for testing and researching components and materials to be used in subsequent fast reactors. The reactor achieved first criticality on July 21, 2010 and started generating power a year later on July 21, 2011. On October 2012 Xinhua announced that the CEFR has passed official checks.
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Following Operation Desert Storm, the criticality and shortage of electronic attack assets was finally recognized. The decision was made to reorganize back to the original three electronic warfare squadrons. In addition, a fourth squadron was gained by activating the reserve Marine Tactical Electronic Warfare Squadron Four (VMAQ-4). While deployed to MCAS Iwakuni, Japan, VMAQ-2 detachment X-ray was re-commissioned as Marine Tactical Electronic Warfare Squadron 1 on July 1, 1992 with the mission to conduct electronic warfare in support of Marine Forces and Joint/Combined operations.
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The critical mass of an uncompressed sphere of bare metal is for uranium-235 and for delta-phase plutonium-239. In practical applications, the amount of material required for criticality is modified by shape, purity, density, and the proximity to neutron-reflecting material, all of which affect the escape or capture of neutrons. To avoid a chain reaction during handling, the fissile material in the weapon must be sub-critical before detonation. It may consist of one or more components containing less than one uncompressed critical mass each.
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It is inherently dangerous to have a weapon containing a quantity and shape of fissile material which can form a critical mass through a relatively simple accident. Because of this danger, the propellant in Little Boy (four bags of cordite) was inserted into the bomb in flight, shortly after takeoff on August 6, 1945. This was the first time a gun-type nuclear weapon had ever been fully assembled. If the weapon falls into water, the moderating effect of the water can also cause a criticality accident, even without the weapon being physically damaged.
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A steady-state (constant power) reactor is operated so that it is critical due to the delayed neutrons, but would not be so without their contribution. During a gradual and deliberate increase in reactor power level, the reactor is delayed-supercritical. The exponential increase of reactor activity is slow enough to make it possible to control the criticality factor, k, by inserting or withdrawing rods of neutron absorbing material. Using careful control rod movements, it is thus possible to achieve a supercritical reactor core without reaching an unsafe prompt-critical state.
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By careful arrangement and the use of various absorber materials, designers can balance the system so one of those neutrons causes another fission event while the other one or two are lost. This balance is known as criticality. Natural uranium is a mix of three isotopes; mainly U-238, with some U-235, and trace amounts of U-234. The neutrons released in the fission of either of the main isotopes will cause fission in U-235, but not in U-238, which requires higher energies around 5 MeV.
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Also, they release on average too few new neutrons per fission, so that with a fuel containing a high fraction of them, criticality cannot be reached. The accelerator driven reactor is independent of this parameter and thus can utilize these nuclides. The three most important long-term radioactive isotopes that could advantageously be handled that way are neptunium-237, americium-241 and americium-243. The nuclear weapon material plutonium-239 is also suitable although it can be expended in a cheaper way as MOX fuel or inside existing fast reactors.
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The neutron balance can be regulated or indeed shut off by adjusting the accelerator power so that the reactor would be below criticality. The additional neutrons provided by the spallation neutron source provide the degree of control as do the delayed neutrons in a conventional nuclear reactor, the difference being that spallation neutron source-driven neutrons are easily controlled by the accelerator. The main advantage is inherent safety. A conventional nuclear reactor's nuclear fuel possesses self-regulating properties such as the Doppler effect or void effect, which make these nuclear reactors safe.
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Not everyone agreed with the decision to use helium. Szilard, in particular, was an early proponent of using liquid bismuth; but the major opponent was Wigner, who argued forcefully in favor of a water-cooled reactor design. He realized that since water absorbed neutrons, k would be reduced by about 3 percent, but had sufficient confidence in his calculations that the water-cooled reactor would still be able to achieve criticality. From an engineering perspective, a water-cooled design was straightforward to design and build, while helium posed technological problems.
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Examiners assess the credit union's risk analysis, policies, and oversight of this area based on the size and complexity of the credit union and the type and volume of e-Commerce services' offered. Examiners consider the criticality of e-Commerce systems and services in their assessment of the overall IS&T; plan. Prompt corrective action may require the development of a net worth restoration plan ("NWRP") in the event the credit union becomes less than adequately capitalized. A NWRP addresses the same basic issues associated with a business plan.
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At 20:05 JST on 12 March, the Japanese government ordered seawater to be injected into Unit 1 in a new effort to cool the reactor core. The treatment had been held as a last resort since it ruins the reactor.SkyNewsHD. Radiation Leaks After Third Japanese Blast TEPCO started seawater cooling at 20:20, adding boric acid as a neutron absorber to prevent a criticality accident. The water would take five to ten hours to fill the reactor core, after which the reactor would cool down in around ten days.
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In applied physics, the concept of controlling self-organized criticality refers to the control of processes by which a self-organized system dissipates energy. The objective of the control is to reduce the probability of occurrence of and size of energy dissipation bursts, often called avalanches, of self-organized systems. Dissipation of energy in a self-organized critical system into a lower energy state can be costly for society, since it depends on avalanches of all sizes usually following a kind of power law distribution and large avalanches can be damaging and disruptive.
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So far, most fast-neutron reactors have used either MOX (mixed oxide) or metal alloy fuel. Soviet fast-neutron reactors use (high enriched) uranium fuel. The Indian prototype reactor uses uranium-carbide fuel. While criticality at fast energies may be achieved with uranium enriched to 5.5 (weight) percent uranium-235, fast reactor designs have been proposed with enrichments in the range of 20 percent for reasons including core lifetime: if a fast reactor were loaded with the minimal critical mass, then the reactor would become subcritical after the first fission.
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Conventional fission power plants rely on the chain reaction caused when nuclear fission events release neutrons that cause further fission events. Each fission event in uranium releases two or three neutrons, so by careful arrangement and the use of various absorber materials, you can balance the system so one of those neutrons causes another fission event while the other one or two are lost. This careful balance is known as criticality. Natural uranium is a mix of several isotopes, mainly a trace amount of U-235 and over 99% U-238.
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Slotin was rushed to the hospital, and died nine days later on 30 May, the victim of the second criticality accident in history, following the death of Harry Daghlian, who had been exposed to radiation by the same core that killed Slotin. Slotin was hailed as a hero by the United States government for reacting quickly enough to prevent the deaths of his colleagues. Some physicists argue that this was a preventable accident. The accident and its aftermath have been dramatized in several fictional and non-fiction accounts.
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The core involved was intended to be used in the Able detonation, during the Crossroads series of nuclear weapon testing. Slotin's experiment was said to be the last conducted before the core's detonation and was intended to be the final demonstration of its ability to go critical. After the criticality accident it needed time to cool. It was therefore rescheduled for the third test of the series, provisionally named Charlie, but this was cancelled due to the unexpected level of radioactivity after the underwater Baker test and the inability to decontaminate the target warships.
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The event was recounted in Dexter Masters' 1955 novel The Accident, a fictional account of the last few days of the life of a nuclear scientist suffering from radiation poisoning. Depictions of the criticality incident include the 1989 film Fat Man and Little Boy, in which John Cusack plays a fictional character named Michael Merriman based on Slotin, and the Louis Slotin Sonata, a 2001 off-Broadway play directed by David P. Moore.Weber, Bruce. A Scientist's Tragic Hubris Attains Critical Mass Onstage (theatre review), The New York Times, 10 April 2001.
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Slotin was the first to propose the name dollar for the interval of reactivity between delayed and prompt criticality; 0 is the point of self-sustaining chain reaction, a dollar is the point at which slowly released, delayed neutrons are no longer required to support chain reaction, and enters the domain called "prompt critical". Stable nuclear reactors operate between 0 and a dollar; excursions and nuclear explosives operate above a dollar. The hundredth part of a dollar is called a cent.Hugh C. Paxton: A History of Critical Experiments at Pajarito Site.
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Given that one of the primary uses of online health communities is the exchange of health information between untrained individuals. In many cases, people do not use the best judgment when sharing and relying on information in online communities, but the consequences of poor information depends on what the information is and how it is used. Medical information can have grave consequences when poor advice is taken or is erroneously applied; or when professional treatment is not sought. The criticality of health-related information necessitates careful consideration of how to design for usability and sociability.
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To prevent any possible nuclear criticality, TEPCO planned to dump boric acid into the reactor and to increase the volume of cooling water by 3 tons per hour.NHK-world (12 February 2012)Temperature rising at No.2 reactor Since only one of the temperature- sensors showed fluctuating readings between 70 °C and 90 °C, TEPCO and NISA thought this sensor was malfunctioning. The sensor works on the principle of changing resistance between the surface of two different metals as the temperature changes. TEPCO planned measurements on this sensor.
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On May 11, 2008, the Nuclear Regulatory Commission released information on emergency notification of two 2006 incidents at the Erwin plant. The first incident involved a leak of liquid containing highly enriched uranium, which could have resulted in a criticality incident. The second incident involved an unmanaged 'accumulation point' - where a critical mass of uranium could have accumulated - was discovered while reacting to the first incident. In other words, no system protections were in place to prevent a solution leak from entering the bottom of an elevator shaft in the plant.
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Article III stipulated that the "reactor and any products resulting from its use will be employed for peaceful purposes only;" at the time, however, there were no effective safeguards to ensure this clause. A further agreement was made with the United States government to supply 21 tons of heavy water for the reactor. Construction of the reactor began later in 1956, with Indian technical personnel sent to Chalk River for training. CIRUS was completed in early 1960 and after achieving criticality in July 1960, was inaugurated by Nehru in January 1961.
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Since the rate of release of these neutrons depends on fission events taking place some time earlier, there is a delay between any power spikes and the later criticality event. This time gives the operators leeway; if a spike in the prompt neutron flux is seen, they have several minutes before this causes a runaway reaction. If a neutron absorber, or neutron poison, is injected at any time during this period, the reactor will shut down. Consequently, the reaction can be controlled with electromechanical control systems such as control rods.
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Upon the first time the Dimona reactor reached criticality in 1963, making it operational, Pazy left his work at the Nuclear Center and continued his studies at the Hebrew University of Jerusalem. Studying mathematics, he conducted his doctoral thesis studies under the guidance of Professor Shmuel Agmon. After completing his PhD studies he accepted a postdoctoral position as an assistant professor at Stanford University and later on at New York University. He returned to Israel in 1969 accepting a position at the Einstein Institute of Mathematics at the Hebrew University of Jerusalem.
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Construction started on 1 January 1951. First criticality was achieved on 6 May 1954, and the first grid connection was made on 27 June 1954. For around four years, until the opening of the Siberian Nuclear Power Station, Obninsk remained the only nuclear power reactor in the Soviet Union; the power plant remained active until 29 April 2002 when it was finally shut down. According to Kotchetkov, in its 48 years of operation there were no significant incidents resulting in personnel overdose or mortality, or radioactive release to the environment exceeding permissible limits.
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Copper Mine The burden that various materials impose on the environment is considered in material criticality. There are numerous negative effects that materials can have on the environment due to either their toxicity, the amounts of energy and water used in processing, and their emissions into the air, water and the land. The purpose of including an evaluation of environmental implications is to transfer information on potential impacts of using a specific material to product designers, government officials, and nongovernmental agencies. The environmental implication evaluation can use data from a source like the Ecoinvent Database.
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Abstract Such small critical mass is favorable for portable nuclear weapons, but those based on 242mAm are not known yet, probably because of its scarcity and high price. The critical masses of two other readily available isotopes, 241Am and 243Am, are relatively high – 57.6 to 75.6 kg for 241Am and 209 kg for 243Am.Institut de Radioprotection et de Sûreté Nucléaire, "Evaluation of nuclear criticality safety data and limits for actinides in transport", p. 16. Scarcity and high price yet hinder application of americium as a nuclear fuel in nuclear reactors.
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Eventually the build-up of fission products that are even more neutron- absorbing than 238U slows the reaction and calls for refuelling. Light water makes an excellent moderator: the light hydrogen atoms are very close in mass to a neutron and can absorb a lot of energy in a single collision (like a collision of two billiard balls). Light hydrogen is also fairly effective at absorbing neutrons, and there will be too few left over to react with the small amount of 235U in natural uranium, preventing criticality.
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This is one of the many reasons for the cooler mass of moderator in the calandria, as even a serious steam incident in the core would not have a major impact on the overall moderation cycle. Only if the moderator itself starts to boil, would there be any significant effect, and the large thermal mass ensures that this will occur slowly. The deliberately "sluggish" response of the fission process in CANDU allows controllers more time to diagnose and deal with problems. The fuel channels can only maintain criticality if they are mechanically sound.
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Because these rods are inserted into the low-pressure calandria, not the high-pressure fuel tubes, they would not be "ejected" by steam, a design issue for many pressurized-water reactors. There are two independent, fast-acting safety shutdown systems as well. Shutoff rods are held above the reactor by electromagnets and drop under gravity into the core to quickly end criticality. This system works even in the event of a complete power failure, as the electromagnets only hold the rods out of the reactor when power is available.
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They were unique in their abandonment of nuclear weapons, and probably also by building gun-type weapons rather than implosion- type weapons. There are also safety problems with gun-type weapons. For example, it is inherently dangerous to have a weapon containing a quantity and shape of fissile material that can form a critical mass through a relatively simple accident. Furthermore, if the weapon is dropped from an aircraft into the sea, then the moderating effect of the seawater can also cause a criticality accident without the weapon even being physically damaged.
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Foster has been critical of the field of visual culture, accusing it of "looseness". In a 1999 article in Social Text, Crimp rebutted Foster, criticizing his notion of the avant-garde and his treatment in The Return of the Real of sexual identity in Andy Warhol's work. Furthermore, this criticality spreads to both the practice and the field of design in his book Design and Crime (2002). Foster views his roles as art critic and art historian as complementary rather than mutually opposed, in accordance with his adherence to postmodernism.
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Criticality in nature is uncommon. At three ore deposits at Oklo in Gabon, sixteen sites (the so-called Oklo Fossil Reactors) have been discovered at which self-sustaining nuclear fission took place approximately 2 billion years ago. Unknown until 1972 (but postulated by Paul Kuroda in 1956), when French physicist Francis Perrin discovered the Oklo Fossil Reactors, it was realized that nature had beaten humans to the punch. Large-scale natural uranium fission chain reactions, moderated by normal water, had occurred far in the past and would not be possible now.
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Fermi then persuaded Compton that he could build the reactor in the squash court under the stands of the University of Chicago's Stagg Field. Construction of the pile began on 6 November 1942, and Chicago Pile-1 went critical on 2 December. The shape of the pile was intended to be roughly spherical, but as work proceeded Fermi calculated that criticality could be achieved without finishing the entire pile as planned. This experiment was a landmark in the quest for energy, and it was typical of Fermi's approach.
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According to the institute's official website, its origins can be traced to as early as 1978 when a group of scholars at Stanford University emphasized the criticality of strengthening the United States-Asia relationship. They stressed that it was necessary to create a hub for the research and study of Asia in regional and global contexts, thus, the Walter H. Shorenstein Asia-Pacific Research Center was founded in 1983. At the time of its founding, it was rendered as a counterpart of the Freeman Spogli Institute for International Studies.
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The Metallurgical Laboratory supplied two large 40-kilowatt reduction furnaces. The Ames Project supplied two tons of uranium metal to the Metallurgical Laboratory for the construction of Chicago Pile-1, the world's first nuclear reactor, which achieved criticality on 2 December 1942. The Ames Project would later supply over 90 percent of the uranium for the X-10 Graphite Reactor at the Clinton Engineer Works in Oak Ridge, Tennessee. Production rose from of uranium metal per day in December 1942 to per day by the middle of January 1943.
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The villages of Muramatsu and Ishigami were created with the establishment of the modern municipalities system on April 1, 1889. On March 31, 1955 the two villages merged to form the village of Tōkai. In 1956, Japan Atomic Energy Research Institute was established at Tōkai. After JRR-1, the first nuclear reactor in Japan, reached criticality, many nuclear-related facilities such as Japan Atomic Energy Agency, Japan Atomic Power Company Tokai Power Station and Tokai No. 2 Power Station have been concentrated in the village, which became the base of the Japanese nuclear industry.
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The highest priority for flood management involved the Los Alamos Critical Experiments Facility (LACEF), a remote site for conducting research in nuclear criticality safety that housed substantial quantities of special nuclear material. The LACEF laboratories were in the bottom of Pajarito Canyon. To protect LACEF, a large, temporary "dry dam" was constructed in the canyon upstream of LACEF to temporarily contain flash floods that might result if an intense thunderstorm happened to rain heavily on the terrain drained by Pajarito Canyon. Runoff was monitored at multiple stations in the headwater streams above Pajarito Canyon.
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Clementine was designed and built in 1945–1946 and first achieved criticality in 1946 and full power in 1949. The reactor was named after the song "Oh My Darling, Clementine." The similarities to the song were that the reactor was located in a deep canyon and the reactor operators were 49'ers, as 49 (last digits of element 94, isotope 239) was one of the code names for plutonium at the time. The primary goal of Clementine was to determine nuclear properties of materials for nuclear weapons research after the Manhattan project.
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Pool design Sodium-Cooled Fast Reactor (SFR) The two largest commercial sodium cooled fast reactors are both in Russia, the BN-600 and the BN-800(800 MW). The largest ever operated was the Superphenix reactor at over 1200 MW of electrical output, successfully operating for a number of years in France before being decommissioned in 1996. In India, the Fast Breeder Test Reactor reached criticality in October 1985. In September 2002, fuel burn up efficiency in the FBTR for the first time reached the 100,000 megawatt-days per metric ton uranium (MWd/MTU) mark.
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In supersymmetric theory of SDEs, stochastic dynamics is defined via stochastic evolution operator acting on the differential forms on the phase space of the model. In this exact formulation of stochastic dynamics, all SDEs possess topological supersymmetry which represents the preservation of the continuity of the phase space by continuous time flow. The spontaneous breakdown of this supersymmetry is the mathematical essence of the ubiquitous dynamical phenomenon known across disciplines as chaos, turbulence, self-organized criticality etc. and the Goldstone theorem explains the associated long-range dynamical behavior, i.e.
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Past pilot and demonstration projects have all used thermal designs with graphite moderators. As such, no true gas-cooled fast reactor design has ever been brought to criticality. The main challenges that have yet to be overcome are in-vessel structural materials, both in-core and out-of-core, that will have to withstand fast-neutron damage and high temperatures (up to 1600 °C). Another problem is the low thermal inertia and poor heat removal capability at low helium pressures, although these issues are shared with thermal reactors which have been constructed.
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On 15 October 1958, there was a criticality accident at one of the research reactors. Six workers received large doses of radiation; one died shortly afterwards. The other five received the first ever bone marrow transplants in Europe.Vinca reactor accident, 1958, compiled by Wm. Robert JohnstonNuove esplosioni a Fukushima: danni al nocciolo. Ue: “In Giappone l’apocalisse”, 14 marzo 2011 Six young researchers, all between 24 and 26 years, were conducting an experiment on the reactor, and the results were to be used by one student for his thesis.
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The other technicians found him there in the snow in a state of ataxia (uncoordinated muscle movement) and only able to say to them, "I'm burning up! I'm burning up!"Event of the excursion during Cecil Kelley criticality accident. Because the possibility of an excursion taking place in a mixing tank had been considered to be virtually non-existent, the technicians decided that Kelley must have somehow been exposed to either alpha radiation, the acid bath, or both, and one of them took him to a chemical shower while the other switched off the mixer.
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Alpha activity would have been widespread if any of the plutonium mixture had escaped from the tank, but none was found. Eighteen minutes later, the team began searching for gamma radiation, and were surprised to find intense gamma radiation near the mixing tank, on the order of tens of rads per hour. Such intense gamma radiation could only be produced by significant amounts of fission product; this, combined with the otherwise inexplicable flash of light reported by the other two technicians, was sufficient to confirm that a criticality accident had occurred.
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In August 2011, a near criticality incident happened with eight rods of plutonium placed close to each other to take a photo. In the aftermath, 12 of 14 of the lab's safety staff left in anger about their advice being dismissed by the management. Without safety management, the Plutonium Facility PF-4 was shut down in 2013 and is still closed in 2017 because the lab fails to meet expectations.The Center for Public Integrity, Patrick Malone: Repeated safety lapses hobble Los Alamos National Laboratory’s work on the cores of U.S. nuclear warheads.
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It is considered unlikely that a reactor's fuel elements would be spread over a wide area, as they are composed of materials such as carbon composites or carbides and are normally coated with zirconium hydride. Before criticality occurs, solid core NTR fuel is not particularly hazardous. Once the reactor has been started for the first time, extremely radioactive short- life fission products are produced, as well as less radioactive but extremely long-lived fission products. Additionally, all engine structures are exposed to direct neutron bombardment, resulting in their radioactive activation.
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Critical Pedagogy Primer is a book by Joe L. Kincheloe published by Peter Lang. Like other "primers" published by Peter Lang, it is an introductory text on the topic of critical pedagogy aimed at a wider audience with its use of more accessible language. The book has wide margins suitable for reader annotations, and many terms and their definitions are included in these margins for accessibility. Kincheloe not only introduces the topic of critical pedagogy, but he makes efforts to visualize the future of critical pedagogy through his notion of "evolving criticality" and the ever-changing field of critical theory.
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In some cases, the heat released by the chain reaction will cause the fissile (and other nearby) materials to expand. In such cases, the chain reaction can either settle into a low power steady state or may even become either temporarily or permanently shut down (subcritical). In the history of atomic power development, at least 60 criticality accidents have occurred, including 22 in process environments, outside nuclear reactor cores or experimental assemblies, and 38 in small experimental reactors and other test assemblies. Although process accidents occurring outside reactors are characterized by large releases of radiation, the releases are localized.
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If a steam explosion occurs in a confined tank of water due to rapid heating of the water, the pressure wave and rapidly expanding steam can cause severe water hammer. This was the mechanism that, in Idaho, USA, in 1961, caused the SL-1 nuclear reactor vessel to jump over in the air when it was destroyed by a criticality accident. In the case of SL-1, the fuel and fuel elements vaporized from instantaneous overheating. Events of this general type are also possible if the fuel and fuel elements of a liquid-cooled nuclear reactor gradually melt.
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The Berkeley Research Reactor was a TRIGA (Training, Research, Isotope production, General Atomics) Mark III open pool reactor with a steady rated thermal power of 1 MW, capable of being pulsed to 2,000 MW. Professor Lawrence Ruby was the chairman of the Nuclear Engineering Reactor Committee and held key roles in the design and analysis of Etcheverry Hall to support reactor licensing, then served as the first reactor supervisor after it was completed. It first achieved criticality on August 10, 1966, and was used for irradiation of various items, as a teaching tool, and to generate radionuclides.
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For this reason the spent fuel storage pools are above the reactor in typical installations. They are shielded by water several times their height, and stored in rigid arrays in which their geometry is controlled to avoid criticality. In the Fukushima reactor incident this became problematic because water was lost from one or more spent fuel pools and the earthquake could have altered the geometry. The fact that the fuel rods' cladding is a zirconium alloy was also problematic since this element can react with steam at extreme temperatures to produce hydrogen, which can ignite with oxygen in the air.
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For the first fifty years after 1945, every published description and drawing of the Little Boy mechanism assumed that a small, solid projectile was fired into the center of a larger, stationary target. However, critical mass considerations dictated that in Little Boy the larger, hollow piece would be the projectile. The assembled fissile core had more than two critical masses of uranium-235. This required one of the two pieces to have more than one critical mass, with the larger piece avoiding criticality prior to assembly by means of shape and minimal contact with the neutron-reflecting tungsten carbide tamper.
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At approximately 14:30 TEPCO announces its belief that the fuel rod storage pool of unit 4 – which is located outside the containment area — may have begun boiling, raising the possibility that exposed rods could reach criticality. By midday NHK TV is reporting white smoke rising from the Fukushima I plant, which officials suggest is likely coming from reactor 3. Shortly afterwards all but a small group of remaining workers at the plant are placed on standby because of the radiation rising to a dangerous level of up to 1 Sv/h. TEPCO temporarily suspended operations at the facility.
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In 1995-1997 publications, Scientific American journalist John Horgan "ridiculed" the movement as being the fourth C among the "failed fads" of "complexity, chaos, catastrophe, and cybernetics". In 1997, Horgan wrote that the approach had "created some potent metaphors: the butterfly effect, fractals, artificial life, the edge of chaos, self organized criticality. But they have not told us anything about the world that is both concrete and truly surprising, either in a negative or in a positive sense."Horgan, John, The End of Science: Facing the Limits of Knowledge in the Twilight of the Scientific Age.
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Neither of these effects is likely with implosion weapons since there is normally insufficient fissile material to form a critical mass without the correct detonation of the lenses. However, the earliest implosion weapons had pits so close to criticality that accidental detonation with some nuclear yield was a concern. On August 9, 1945, Fat Man was loaded onto its airplane fully assembled, but later, when levitated pits made a space between the pit and the tamper, it was feasible to use in-flight pit insertion. The bomber would take off with no fissile material in the bomb.
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Prompt- critical assemblies are created by design in nuclear weapons and some specially designed research experiments. When differentiating between a prompt neutron versus a delayed neutron, the difference between the two has to do with the source from which the neutron has been released into the reactor. The neutrons, once released, have no difference except the energy or speed which have been imparted to them. A nuclear weapon relies heavily on prompt- supercriticality (to produce a high peak power in a fraction of a second), whereas nuclear power reactors use delayed-criticality to produce controllable power levels for months or years.
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Because of its remote location, Fort Greely was chosen as one of the first US military posts to have a compact, nuclear power reactor to generate heat and electricity, under the auspices of the Army Nuclear Power Program. A nuclear power plant, designated the SM-1A was flown in and installed between 1960–62, and was based on the Army's first prototype reactor, the SM-1 at Fort Belvoir, Virginia. SM-1A pressurized-water reactor reached initial criticality on 13 March 1962, and was shut down in 1972: the reactor core was removed and sent to the Savannah River nuclear site.
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The CANDU design addresses the moderation problem by replacing the normal water with heavy water. Heavy water already has an extra neutron, so the chance that a fission neutron will be absorbed during moderation is largely eliminated. Additionally, it is subject to other reactions that further increase the number of neutrons released during operation. The neutron economy is improved to the point where even unenriched natural uranium will maintain criticality, which greatly reduces the complexity and cost of fueling the reactor, and also allows it to use a number of alternative fuel cycles that mix in even less reactive elements.
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However, in fact the vast majority of wooden aircraft built in recent decades (mostly amateur-built aircraft) instead use other types of adhesives (primarily epoxy resin systems), which offer greater strength and, even more importantly, much less criticality in perfect application technique. Most newer adhesives are much more tolerant to typical construction mistakes (such as small gaps or misalignments between parts) than resorcinol, which offers virtually no tolerance for such everyday construction situations. This can pose major difficulties, especially in complex assemblies. Resorcinol is, however, still used by some builders/restorers, and is commonly seen in vintage aircraft.
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In any case, criticality then depends upon a typical neutron "seeing" an amount of nuclei around it such that the areal density of nuclei exceeds a certain threshold. This is applied in implosion-type nuclear weapons where a spherical mass of fissile material that is substantially less than a critical mass is made supercritical by very rapidly increasing ρ (and thus Σ as well) (see below). Indeed, sophisticated nuclear weapons programs can make a functional device from less material than more primitive weapons programs require. Aside from the math, there is a simple physical analog that helps explain this result.
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Several strategies have been proposed to deal with the issue of controlling self- organized criticality: #The design of controlled avalanches. Daniel O. Cajueiro and Roberto F. S. Andrade show that if well-formulated small and medium avalanches are exogenously triggered in the system, the energy of the system is released in a way that large avalanches are rarer. # The modification of the degree of interdependence of the network where the avalanche spreads. Charles D. Brummitt, Raissa M. D'Souza and E. A. Leicht show that the dynamics of self-organized critical systems on complex networks depend on connectivity of the complex network.
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HVAC commissioning, historically, didn't include other, interactive, supporting, or supplemental building systems that did not directly affect the performance of the HVAC systems. Through energy and water conservation, occupant comfort, life-safety, systems criticality, and technology improvements of building systems became more in demand, and expanded the Owner's performance and technical capability expectation. The need to improve, integrate, and commission other (and more) systems expanded the scope of Building Commissioning. In modern facilities, buildings, and systems many of the systems are integrated (directly or indirectly) in operation, affect, need for proper operation, function, control, and sequencing.
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The combination of reduced weight in relation to yield and immunity to radiation has ensured that most modern nuclear weapons are fusion-boosted. The fusion reaction rate typically becomes significant at 20 to 30 megakelvins. This temperature is reached at very low efficiencies, when less than 1% of the fissile material has fissioned (corresponding to a yield in the range of hundreds of tons of TNT). Since implosion weapons can be designed that will achieve yields in this range even if neutrons are present at the moment of criticality, fusion boosting allows the manufacture of efficient weapons that are immune to predetonation.
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Senator Tom Harkin highlighted the criticality of the issue, stating: "...we need Rory's Regulations in every state so that they can recognize sepsis." On September 17, 2014, The Rory Staunton Foundation held the first ever Sepsis Forum in Washington D.C. attended by Senator Charles Schumer (D-NY); Thomas Frieden M.D., Director CDC; Patrick Conway, M.D., CMS Chief Medical Officer; Congressman Joseph Crowley; and Kevin Tracey M.D. Director, Feinstein Institute. In November 2014, the Staunton family met with U.S. Health Secretary, Sylvia Mathews Burwell and addressed the opening session of the CMS Health Conference in Baltimore, Maryland.
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These rods are normally held out of the critical region by the upward pressure of the pumped salt in circulation but will drop into place to stop criticality if pumped circulation is lost due to a power outage or pump failure. As with other molten salt reactors, the reactor can also be shut down by draining the fuel salt from the Core-unit into storage tanks. A failsafe backup is provided in the form of meltable cans, filled with a liquid neutron absorbing material that will permanently shut down the reactor in the event of a severe overheating event.
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The Internet, a short form of the word Internetwork, is an international ubiquitous network of networks. Given the amount of data traversing it, its criticality to personal, corporate and national security cannot be over- emphasized. The Internet infrastructure comprises software-driven networked switches, routers, firewalls, servers and storage hardware that switch, route, protect and store all voice, video and text data intelligently across the world. Internet equipment manufacturers like Cisco Systems, Hewlett-Packard, etc.. have a quasi monopoly on the multi-Billion dollar software maintenance services market for networking equipment through their own maintenance contracts and authorized third party maintenance.
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It was assembled by plutonium rings and had a hollow volume inside that measured about 0.5 cm in diameter. This central volume was lined with copper, which like the liner in the primary's fissile core prevented DT gas diffusion in plutonium. The spark plug's boosting charge contained about 4 grams of tritium and, imploding together with the secondary's compression, was timed to detonate by the first generations of neutrons that arrived from the primary. Timing was defined by the geometric characteristics of the sparkplug (its uncompressed annular radius), which detonated when its criticality, or k, transcended 1.
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The experiment was originally located at the Los Alamos National Laboratory Critical Experiments Facility (LACEF) located at the Los Alamos Pajarito Site, otherwise known as Technical Area 18. In 2005 the Pajarito Site started to shut down and nuclear material was moved to the National Criticality Experiments Research Center (NCERC) which is located at the Nevada National Security Site. However, NCERC continues to be operated by the Los Alamos National Laboratory. The core capabilities at NCERC include Flattop along with three other critical assemblies, Comet, Planet, and Godiva- IV and a significant inventory of nuclear material items available for experimental use.
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While Einstein equations seem to appear somewhat out of place, nevertheless this result is surely striking showing as a background two-dimensional model could produce higher-dimensional physics. An interesting point here is that such a string theory can be formulated without a requirement of criticality at 26 dimensions for consistency as happens on a flat background. This is a serious hint that the underlying physics of Einstein equations could be described by an effective two-dimensional conformal field theory. Indeed, the fact that we have evidence for an inflationary universe is an important support to string cosmology.
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SL-1 - Dismantling of the foundation piers Idaho National Laboratory near Arco, Idaho was founded in 1949 as a nuclear reactor testing laboratory. Some consider it to be the site of the first fatal accident in the nuclear military/industrial sector when the SL-1 boiling water reactor melted down, killing two reactor operators, a third operator died shortly thereafter. When a control rod in the reactor was removed manually causing a power surge and ensuing criticality, a steam explosion occurred in the reactor vessel. The event caused the reactor lid to be blown nine feet into the air.
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This means that cooling the core with water from nearby sources will not add to the reactivity of the fuel mass. Normally the rate of fission is controlled by light-water compartments called liquid zone controllers, which absorb excess neutrons, and by adjuster rods, which can be raised or lowered in the core to control the neutron flux. These are used for normal operation, allowing the controllers to adjust reactivity across the fuel mass, as different portions would normally burn at different rates depending on their position. The adjuster rods can also be used to slow or stop criticality.
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What a SIS shall do (the functional requirements) and how well it must perform (the safety integrity requirements) may be determined from Hazard and operability studies (HAZOP), layers of protection analysis (LOPA), risk graphs, and so on. All techniques are mentioned in IEC 61511 and IEC 61508. During SIS design, construction, installation, and operation, it is necessary to verify that these requirements are met. The functional requirements may be verified by design reviews, such as failure modes, effects, and criticality analysis (FMECA) and various types of testing, for example factory acceptance testing, site acceptance testing, and regular functional testing.
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The Swendsen-Wang algorithm is the first non-local or cluster algorithm for Monte Carlo simulation for large systems near criticality. It has been introduced by Robert Swendsen and Jian-Sheng Wang in 1987 at Carnegie Mellon. The original algorithm was designed for the Ising and Potts models, and it was later generalized to other systems as well, such as the XY model by Wolff algorithm and particles of fluids. The key ingredient was the random cluster model, a representation of the Ising or Potts model through percolation models of connecting bonds, due to Fortuin and Kasteleyn.
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IP PBX is primarily a software hosted on a regular desktop or server as per the requirement demands based on the expected traffic & criticality. Till 2019 IP PBX were deployed primarily as inbound and outbound call center solutions for large corporate and commercial cloud telephony operators worldwide cloud communications. Most of the IP PBX installation uses Asterisk (PBX) for its telephony support, built on LAMP (Linux-Apache-MySQL-PHP). With telecom service providers across the world is slowly preferring SIP Trunks over Primary Rate Interface as main enterprise communication delivery, the IP PBXs will now be in demand extensively.
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If the heat cannot be removed from the reactor, the fuel rods may overheat and release radioactive materials. Thirdly, a criticality accident (a rapid increase of the reactor power) is possible in certain reactor designs if the chain reaction cannot be controlled. These three characteristics have to be taken into account when designing nuclear reactors. All modern reactors are designed so that an uncontrolled increase of the reactor power is prevented by natural feedback mechanisms: if the temperature or the amount of steam in the reactor increases, the fission rate inherently decreases by designing in a negative void coefficient of reactivity.
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Believed at first to be a running joke at the precinct, "the Rumor" was blamed for unexplained events or used as a transparent excuse ("I was waiting for the Rumor to show up"). When Toybox was trapped under a collapsed part of the station, however, he appeared to her as a translucent, featureless humanoid. Five years after the Ultima incident, the Rumor eventually reveals his ultimate role as multiversal "criticality adjuster," applying slight adjustments to pivotal moments to effect a positive outcome. He can access superspace, the underlying connective region of the multiverse, to traverse great distances.
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Traditional criticality analyses assume that the fissile material is in its most reactive condition, which is usually at maximum enrichment, with no irradiation. For spent nuclear fuel storage and transport, burnup credit may be used to allow fuel to be more closely packed, reducing space and allowing more fuel to be handled safely. In order to implement burnup credit, fuel is modeled as irradiated using pessimistic conditions which produce an isotopic composition representative of all irradiated fuel. Fuel irradiation produces actinides consisting of both neutron absorbers and fissionable isotopes as well as fission products which absorb neutrons.
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Daniel P. MeuserDaniel P. Meuser Resumé and Biography (born February 10, 1964) is an American businessman and politician who serves as the U.S Representative in Pennsylvania's 9th congressional district. A Republican, he previously served as the Secretary of Revenue in the cabinet of Pennsylvania Governor Tom Corbett. He was previously President of the Pride Mobility Corporation, a manufacturer of motorized wheelchairs in the Wilkes-Barre/Scranton metro area of Pennsylvania, and currently serves the company as a board member and consultant. He has previously testified before Congress regarding the criticality for federal practices surrounding rights and caring for the disabled.
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The Shearon Harris Nuclear Power Plant is a nuclear power plant with a single Westinghouse designed pressurized-water nuclear reactor operated by Duke Energy. It was named in honor of W. Shearon Harris, former president of Carolina Power & Light (predecessor of Progress Energy Inc.). Located in New Hill, North Carolina, in the United States, about 20 miles (30 km) southwest of Raleigh, it generates 900 MWe, has a 523-foot (160 m) natural draft cooling tower, and uses Harris Lake for cooling. The reactor achieved criticality in January 1987 and began providing power commercially on May 2 of that year.
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The electricity produced was more expensive than that of a conventional coal-fired plant, but this was offset by the value of the plutonium produced, which was about £100 per gram (£3,100 per ounce). Construction of the first PIPPA commenced at Calder Hall in March 1953. For cost reasons PIPPA was to operate in such a way that there would be a higher proportion of plutonium-240 present with the plutonium-239 product than in the Windscale-produced material. Since plutonium-240 is prone to spontaneous fission, this increased the risk of criticality accident and a fizzle that would reduce the yield.
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He finishes by bringing together two bars of plutonium he has removed from Northmoor, causing a criticality accident and irradiating himself and the nearby Grogan. Emma's ghost appears to Craven and tells him of a time when black flowers grew, warming the Earth and preventing life from becoming extinct. She tells him that the black flowers have returned and will melt the polar icecaps, destroying mankind so that life can continue. Craven goes to dissuade Jedburgh from the next step in his plan, which is to cause a nuclear explosion in Scotland with the rest of the plutonium.
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Joint work with Richard Bagley produced a simulation of an autocatalytic set of polymers in which a few species are maintained at high concentration, with many of the properties of a metabolism; the autocatalytic set evolved through time in a manner resembling the evolution of living systems, but without a genetic code. James Keeler and Farmer demonstrated that a system of coupled logistic maps could produce fluctuations with a 1/f power spectrum. They showed that this occurred because the system continually tunes itself to stay near a critical point, a property that was later dubbed self-organized criticality by Per Bak.
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Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed the first atomic bombs. The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores. Human radiation experiments studying plutonium were conducted without informed consent, and several criticality accidents, some lethal, occurred after the war. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern.
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The original interest behind the model stemmed from the fact that in simulations on lattices, it is attracted to its critical state, at which point the correlation length of the system and the correlation time of the system go to infinity, without any fine tuning of a system parameter. This contrasts with earlier examples of critical phenomena, such as the phase transitions between solid and liquid, or liquid and gas, where the critical point can only be reached by precise tuning (e.g., of temperature). Hence, in the sandpile model we can say that the criticality is self-organized.
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A criticality accident occurred on December 30, 1958, at the Los Alamos National Laboratory in Los Alamos, New Mexico, in the United States. It is one of only ten such events that have occurred outside a nuclear reactor, though it was the third such event that took place in 1958 after events on 16 June Y-1234. at the Y-12 Plant in Oak Ridge, Tennessee, and on 15 October at the Vinča Nuclear Institute in Vinča, Yugoslavia. The accident involved plutonium compounds dissolved in liquid chemical reagents; within 35 hours, it killed chemical operator Cecil Kelley by severe radiation poisoning.
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Practical engineering designs must first take into account safety as the primary goal. All designs should incorporate passive cooling in combination with refractory materials to prevent melting and reconfiguration of fissionables into geometries capable of un-intentional criticality. Blanket layers of Lithium bearing compounds will generally be included as part of the design to generate Tritium to allow the system to be self-supporting for one of the key fuel element components. Tritium, because of its relatively short half-life and extremely high radioactivity, is best generated on site to obviate the necessity of transportation from a remote location.
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In a topological transcriptome analysis, researchers profiled important proteins of the non-small cell lung cancer regulatory network and determined that TMEM125 exhibited different topological characteristics across cancerous and normal conditions, suggesting its criticality in lung cancer networks. This is consistent with post- translational modification analysis; TMEM125 phosphorylation suggests it may be involved in a signal transduction pathway or as a receptor protein. Additionally, its myristoylation sites suggests its involvement in signal transduction, apoptosis, and alternative extracellular protein export. TMEM125 was identified as a tetraspanin cell adhesion molecule enriched in oligodendrocytes, suggesting it may play a role in myelination.
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Under normal circumstances, a critical or supercritical fission reaction (one that is self- sustaining in power or increasing in power) should only occur inside a safely shielded location, such as a reactor core or a suitable test environment. A criticality accident occurs if the same reaction is achieved unintentionally, for example in an unsafe environment or during reactor maintenance. Though dangerous and frequently lethal to humans within the immediate area, the critical mass formed would not be capable of producing a massive nuclear explosion of the type that fission bombs are designed to produce. This is because all the design features needed to make a nuclear warhead cannot arise by chance.
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Rostov Nuclear Power Plant ( []), also known as Volgodonsk Nuclear Power Plant ( []), is a Russian nuclear power plant located on the left bank of the Tsimlyansk reservoir in the lower stream of the Don River near Volgodonsk, Rostov Oblast. Construction of Rostov reactor No. 1 began in 1977 and operations began in 2001. Construction of reactor No. 2 commenced in 1983 and finished in 2010. Unit 3 was connected to the electrical grid for the first time in December 2015. Unit 4 underwent first criticality on 7 December 2017, and put into commercial operation on 28 September 2018. Units No. 3 and 4 are of an upgraded VVER-1000/320 subtype.
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Zirconium crystal bar and cube During his early years at the DAE, Sundaram was in charge of the production of zirconium, beryllium, titanium, tantalum and other refractory metals and he contributed to the establishment of a production facility at Nuclear Fuel Complex which produced zirconium sponge, niobium and tantalum metal products. He oversaw the project from research to production, including the setting up of a pilot plant. Later, when he moved to IGCAR, he took over the Fast Breeder Test Reactor (FBTR) project and it was during his tenancy as the director, the reactor reached criticality, in 1985. Subsequently, he guided the Prototype Fast Breeder Reactor project until his retirement.
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Rather, they opted to keep the problem within their reporting channels with the SRBs' contractor, Thiokol. Even after the O-rings were redesignated as "Criticality 1"—meaning that their failure would result in the destruction of the Orbiter—no one at Marshall suggested that the shuttles be grounded until the flaw could be fixed. As a result, no one in NASA's senior management knew about the dimensions of the problem until a NASA auditor discovered a contract for a redesigned SRB in a 1985 budget report. Following the Challenger tragedy, a longtime Marshall Center manager, known as "Apocalypse," wrote a letter to the center's inspector general detailing Lucas' management style.
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Richard Palais (right) and Chuu-Lian Terng (wife) at Oberwolfach, 2010 Richard Sheldon Palais (born May 22, 1931) is a mathematician working in geometry who introduced the Principle of Symmetric Criticality, the Mostow–Palais theorem, the Lie–Palais theorem, the Morse–Palais lemma, and the Palais–Smale compactness condition. From 1965 to 1967 Palais was a Sloan Fellow. In 1970 he was an invited speaker (Banach manifolds of fiber bundle sections) at the International Congress of Mathematicians in Nice. From 1965 to 1982 he was an editor for the Journal of Differential Geometry and from 1966 to 1969 an editor for the Transactions of the American Mathematical Society.
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Strengths of FMECA include its comprehensiveness, the systematic establishment of relationships between failure causes and effects, and its ability to point out individual failure modes for corrective action in design. Weaknesses include the extensive labor required, the large number of trivial cases considered, and inability to deal with multiple-failure scenarios or unplanned cross-system effects such as sneak circuits. According to an FAA research report for commercial space transportation, :Failure Modes, effects, and Criticality Analysis is an excellent hazard analysis and risk assessment tool, but it suffers from other limitations. This alternative does not consider combined failures or typically include software and human interaction considerations.
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This led to a renewal of physiology in the 1980s through the application of chaos theory, for example, in the study of pathological cardiac cycles. In 1987, Per Bak, Chao Tang and Kurt Wiesenfeld published a paper in Physical Review Letters However, the conclusions of this article have been subject to dispute. . See especially: describing for the first time self- organized criticality (SOC), considered one of the mechanisms by which complexity arises in nature. Alongside largely lab-based approaches such as the Bak–Tang–Wiesenfeld sandpile, many other investigations have focused on large-scale natural or social systems that are known (or suspected) to display scale-invariant behavior.
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Typically, control rods contain neutron poisons (substances, for example boron or hafnium, that easily capture neutrons without producing any additional ones) as a means of altering k-effective. With the exception of experimental pulsed reactors, nuclear reactors are designed to operate in a delayed- critical mode and are provided with safety systems to prevent them from ever achieving prompt criticality. In a delayed-critical assembly, the delayed neutrons are needed to make k-effective greater than one. Thus the time between successive generations of the reaction, T, is dominated by the time it takes for the delayed neutrons to be released, on the order of seconds or minutes.
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In December, the regents awarded the construction contract to Jentoft & Forbes, paying $308,082 (equivalent to $ in dollars) for the project. A site at the eastern edge of the campus was chosen for its proximity to various academic engineering buildings and its visibility to the public. The AEC granted an operating license for the reactor to the university in April 1961, and the reactor began operating with a self- sustained nuclear reaction on April 10. It was officially dedicated on June 1, in a ceremony attended by Argonne National Laboratory director Norman Hilberry, a physicist who worked on Chicago Pile-1, the world's first nuclear reactor to achieve criticality.
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The Pentagon's SOF developed the CARVER matrix to target weaknesses in enemy and friendly targets The CARVER matrix was developed by the United States Army Special Forces during the Vietnam War. CARVER is an acronym that stands for Criticality, Accessibility, Recuperability, Vulnerability, Effect and Recognizability and is a system to identify and rank specific targets so that attack resources can be efficiently used. CARVER was developed in World War II by the OSS for the French field agents as a simple, uniformly and somewhat quantifiable means of selecting targets for possible interdiction. CARVER can be used from an offensive (what to attack) or defensive (what to protect) perspective.
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It first reached criticality in October 1985, making India the seventh nation to have the technology to build and operate a breeder reactor after United States, UK, France, Japan, Germany, and Russia. The reactor was designed to produce 40 MW of thermal power and 13.2 MW of electrical power. The FBTR has rarely operated at its designed capacity and had to be shut down between 1987 and 1989 due to technical problems. From 1989 to 1992, the reactor operated at 1 MW. In 1993, the reactor's power level was raised to 10.5 MW. The initial nuclear fuel core used in the FBTR consisted of approximately 50 kg of weapons-grade plutonium.
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The CHF condition (or simply the CHF) is the most widely used today, though it may mislead one to think that there exists a criticality in the heat flux. The terms denoting the value of heat flux at the CHF occurrence are CHF, dryout heat flux, burnout heat flux, maximum heat flux, DNB heat flux, etc. The term peak pool boiling heat flux is also used to denote the CHF in pool boiling. Post-CHF is used to denote the general heat transfer deterioration in flow boiling process, and liquid could be in the form of dispersed spray of droplets, continuous liquid core, or transition between the former two cases.
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Often the simplest moderator to use is normal water; when a neutron collides with a water molecule it transfers some of its energy to it, increasing the temperature of the water and slowing the neutron. The main problem with using normal water as a moderator is that it also absorbs some of the neutrons. The neutron balance in the natural isotopic mix is so close that even a small number being absorbed in this fashion means there are too few to maintain criticality. In most reactor designs this is addressed by slightly increasing the amount of 235U relative to 238U, a process known as enrichment.
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A nuclear fuel pellet Nuclear fuel pellets that are ready for fuel assembly completion The use of ordinary water makes it necessary to do a certain amount of enrichment of the uranium fuel before the necessary criticality of the reactor can be maintained. The light-water reactor uses uranium 235 as a fuel, enriched to approximately 3 percent. Although this is its major fuel, the uranium 238 atoms also contribute to the fission process by converting to plutonium 239; about one- half of which is consumed in the reactor. Light-water reactors are generally refueled every 12 to 18 months, at which time, about 25 percent of the fuel is replaced.
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The power plant was built by Siemens and went online on May 19, 1972 shortly after having reached the first criticality on January 8, 1972.Power Reactor Information System der IAEA: „Germany, Federal Republic of: Nuclear Power Reactors“ (englisch) Between March, 1972 and November, 2003 the plant supplied electrical power of 662 MW (internal) / 630 MW (external), as well as 1,892 MW thermal power. Until September 7, 2005, the power plant ran in "post- operational" mode, and has been in "residual" mode since then. In 31 years of operation, 157 fuel elements were consumed, including, from December 15, 1988 onwards, fuel elements containing 4% uranium.
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In parallel with the planning of Beznau 1, the then Bernische Kraftwerke AG decided to build a second nuclear power plant in the canton of Berne. Mühleberg was identified as possible location and the Swiss Federal Office of Energy (SFOE) approved this choice on 21 July 1965. Two years later, on 21 March 1967, a first partial construction permit was issued, followed on 7 March 1968 by the final one. The reactor entered criticality in March 1971 but, due to a fire in the turbine housing, the plant had to be shut down for repairs. It started commercial operation on 6 November 1972.. In German.
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In a smaller scale accident at Sarov a technician working with highly enriched uranium was irradiated while preparing an experiment involving a sphere of fissile material. The Sarov accident is interesting because the system remained critical for many days before it could be stopped, though safely located in a shielded experimental hall. This is an example of a limited scope accident where only a few people can be harmed, while no release of radioactivity into the environment occurred. A criticality accident with limited off site release of both radiation (gamma and neutron) and a very small release of radioactivity occurred at Tokaimura in 1999 during the production of enriched uranium fuel.
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Scientists from LANL and VNIIEF have cooperated on various arms control and nuclear safeguards programs, under which the Los Alamos scientists learned, to their amusement, that their Russian colleagues paid homage to their American rivals by irreverently calling their own laboratory "Los Arzamas." Boris Yeltsin changed the town's name back to Sarov at the request of the residents in August 1995. On June 17, 1997, a Russian Federal Nuclear Center senior researcher Alexandr Zakharov received a fatal dose of 4850 rem in a criticality accident. During the 2010 Russian wildfires the Russian Army took preventive forest fire measures and radioactive material was reported to have been secured elsewhere.
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Sampling in 1994 revealed concentrations of uranium that created a potential for a nuclear criticality accident, as well as a potentially dangerous build-up of fluorine gas – the environment above the solidified salt was approximately one atmosphere of fluorine. The ensuing decontamination and decommissioning project was called "the most technically challenging" activity assigned to Bechtel Jacobs under its environmental management contract with the U.S. Department of Energy's Oak Ridge Operations organization. In 2003, the MSRE cleanup project was estimated at about $130 million, with decommissioning expected to be completed in 2009.R. Cathey Daniels, Elegant experiment puts wallop on cleanup, The Oak Ridger, April 8, 2003.
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Until 1955 known under a secret name "Laboratory No. 2 of the USSR Academy of Sciences", the Kurchatov Institute was founded in 1943 with the initial purpose of developing nuclear weapons. The majority of Soviet nuclear reactors were designed in the Institute, including the on-site F-1, which was the first nuclear reactor outside North America to sustain criticality. Since 1955 it was also the host for major scientific experimental work in the fields of thermonuclear fusion and plasma physics. In particular, the first tokamak systems were developed there, the most successful of them being T-3 and its larger version T-4.
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When they undergo fission, both of these isotopes release fast neutrons with an energy distribution peaking around 1 to 2 MeV. This energy is too low to cause fission in U-238, which means it cannot sustain a chain reaction. U-235 will undergo fission when struck by neutrons of this energy, so it is possible for U-235 to sustain a chain reaction, as is the case in a nuclear bomb. However, there is too little U-235 in a mass of natural uranium, and the chance any given neutron will cause fission in these isolated atoms is not high enough to reach criticality.
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Because Falb proceeded to claim each of these days to be preceded and followed by 2–3 days which he also considered critical (though less so), about a third of all days of the year met some criteria of "criticality" according to the lunisolar hypothesis. Moreover, by stating the actual occurrence of the predicted events not to be mandatory, Falb immunized himself against failures while he could (and would) always claim successes as being in support of his hypothesisBrückner E. Weather prophets. In: The Sources and Consequences of Climate Change and Climate Variability in Historical Times, p. 246–248. Ed.: Kluwer Academic Publishers—a characteristic hallmark of predictions in pseudoscience.
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Self- organized criticality (SOC) is a statistical physics concept to describe a class of dynamical systems that have a critical point as an attractor. Specifically, these are non-equilibrium systems that evolve through avalanches of change and dissipations that reach up to the highest scales of the system. SOC is said to govern the dynamics behind some natural systems that have these burst-like phenomena including landscape formation, earthquakes, evolution, and the granular dynamics of rice and sand piles. Of special interest here is the Bak–Sneppen model of SOC, which is able to describe evolution via punctuated equilibrium (extinction events) – thus modelling evolution as a self-organised critical process.
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In early November, Fermi came to Compton with a proposal to build the experimental pile under the stands at Stagg Field. CP-1 under construction: 4th layer The risk of building an operational reactor running at criticality in a populated area was a significant issue, as there was a danger of a catastrophic nuclear meltdown blanketing one of the United States' major urban areas in radioactive fission products. But the physics of the system suggested that the pile could be safely shut down even in the event of a runaway reaction. When a fuel atom undergoes fission, it releases neutrons that strike other fuel atoms in a chain reaction.
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The lid was laid incorrectly and had to be lifted again with the control rods attached. A beam was supposed to prevent the lid from being lifted too far, but this beam was positioned incorrectly, and the lid with control rods was lifted up too far. At 10:55 AM the starboard reactor became prompt critical, resulting in a criticality excursion of about 5·1018 fissions and a thermal/steam explosion. The explosion expelled the new load of fuel, destroyed the machine enclosures, ruptured the submarine's pressure hull and aft bulkhead, and partially destroyed the fuelling shack, with the shack's roof falling 70 metres away in the water.
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Software criticality levels range from A to E, corresponding to the severity of Catastrophic to No Safety Effect. Higher levels of rigor are required for level A and B software and corresponding functional tasks and work products is the system safety domain are used as objective evidence of meeting safety criteria and requirements. Recently a leading edge commercial standard was promulgated based on decades of proven system safety processes in DoD and NASA. ANSI/GEIA-STD-0010-2009 (Standard Best Practices for System Safety Program Development and Execution) is a demilitarized commercial best practice that uses proven holistic, comprehensive and tailored approaches for hazard prevention, elimination and control.
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These were then mixed with the graphite and pressed together to form blocks of various shapes and sizes. Criticality is only possible when the blocks are placed together in certain configurations within a neutron reflector, allowing additional fuel to be held in a ready area and loaded on- the-fly. Helium was used due to its low nuclear cross section which led to higher neutron economy, as well as its chemical inertness allowing it to operate at higher temperatures without fear of eroding the reactor materials. Higher temperatures also allow for more efficient steam turbine operation and make it more suitable for direct use as process heat.
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Masters co-edited with nuclear physicist Katharine Way (1903-1995) the 1946 New York Times bestseller One World or None: a Report to the Public on the Full Meaning of the Atomic Bomb. The book included essays by Niels Bohr, Albert Einstein, and J. Robert Oppenheimer, and sold over 100,000 copies. In 1955, Masters published a novel, The Accident, detailing the last eight days of a nuclear physicist dying from radiation sickness after a criticality accident, based on the death of physicist Louis Slotin who died after such an accident in 1946. The novel was so controversial the US banned a movie version of it.
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During operation of a reactor the amount of fuel contained in the core decreases monotonically. If the reactor is to operate for a long period of time, fuel in excess of that needed for exact criticality must be added when the reactor is fueled. The positive reactivity due to the excess fuel must be balanced with negative reactivity from neutron-absorbing material. Movable control rods containing neutron-absorbing material is one method, but control rods alone to balance the excess reactivity may be impractical for a particular core design as there may be insufficient room for the rods or their mechanisms, namely in submarines, where space is particularly at a premium.
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The key to maintaining a nuclear chain reaction within a nuclear reactor is to use, on average, exactly one of the neutrons released from each nuclear fission event to stimulate another nuclear fission event (in another fissionable nucleus). With careful design of the reactor's geometry, and careful control of the substances present so as to influence the reactivity, a self-sustaining chain reaction or "criticality" can be achieved and maintained. Natural uranium consists of a mixture of various isotopes, primarily 238U and a much smaller amount (about 0.72% by weight) of 235U. 238U can only be fissioned by neutrons that are relatively energetic, about 1 MeV or above.
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They also present a nuclear proliferation concern; the same systems used to enrich the 235U can also be used to produce much more "pure" weapons-grade material (90% or more 235U), suitable for producing a nuclear weapon. This is not a trivial exercise by any means, but feasible enough that enrichment facilities present a significant nuclear proliferation risk. An alternative solution to the problem is to use a moderator that does not absorb neutrons as readily as water. In this case potentially all of the neutrons being released can be moderated and used in reactions with the 235U, in which case there is enough 235U in natural uranium to sustain criticality.
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Though the Schrödinger group is defined as symmetry group of the free particle Schrödinger equation, it is realized in some interacting non-relativistic systems (for example cold atoms at criticality). The Schrödinger group in d spatial dimensions can be embedded into relativistic conformal group in d+1 dimensions SO(2,d+2). This embedding is connected with the fact that one can get the Schrödinger equation from the massless Klein–Gordon equation through Kaluza–Klein compactification along null-like dimensions and Bargmann lift of Newton–Cartan theory. This embedding can also be viewed as the extension of the Schrödinger algebra to the maximal parabolic sub-algebra of SO(2,d+2).
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The core characteristic of the entities targeted by ISO/IEC 29110 is size, however there are other aspects and characteristics of VSEs that may affect profile preparation or selection, such as: Business Models (commercial, contracting, in-house development, etc.); Situational factors (such as criticality, uncertainty environment, etc.); and Risk Levels. Creating one profile for each possible combination of values of the various dimensions introduced above would result in an unmanageable set of profiles. Accordingly, VSE's profiles are grouped in such a way as to be applicable to more than one category. Profile Groups are a collection of profiles which are related either by composition of processes (i.e.
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Einsteinium has a high rate of nuclear fission that results in a low critical mass for a sustained nuclear chain reaction. This mass is 9.89 kilograms for a bare sphere of 254Es isotope, and can be lowered to 2.9 by adding a 30-centimeter-thick steel neutron reflector, or even to 2.26 kilograms with a 20-cm-thick reflector made of water. However, even this small critical mass greatly exceeds the total amount of einsteinium isolated thus far, especially of the rare 254Es isotope.Institut de Radioprotection et de Sûreté Nucléaire, "Evaluation of nuclear criticality safety data and limits for actinides in transport", p. 16.
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Its critical mass is relatively high at 192 kg; it can be reduced with a water or steel reflector but would still exceed the world production of this isotope.Institut de Radioprotection et de Sûreté Nucléaire: "Evaluation of nuclear criticality safety. data and limits for actinides in transport" , p. 16 Berkelium-247 can maintain chain reaction both in a thermal-neutron and in a fast-neutron reactor, however, its production is rather complex and thus the availability is much lower than its critical mass, which is about 75.7 kg for a bare sphere, 41.2 kg with a water reflector and 35.2 kg with a steel reflector (30 cm thickness).
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The standardized interfaces within the FACE Reference Architecture are the Operating System Segment Interface (OSS Interface), the Input/Output Services Interface (IOS Interface), the Transport Services Interfaces, and Component-Oriented Support Interfaces. The FACE Reference Architecture defines three FACE OSS Profiles tailoring the Operating System (OS) Application Programming Interfaces (APIs), programming languages, programming language features, run-times, frameworks, and graphics capabilities to meet the requirements of software components for differing levels of criticality. The three Profiles are Security, Safety, and General Purpose. The Security Profile constrains the OS APIs to a minimal useful set allowing assessment for high-assurance security functions executing as a single process.
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" Development of the CFDI was planned in three phases, on an annual and ongoing basis. The first phase was identification, beginning with "the first-ever National Critical Foreign Dependencies List in FY2008". This was done by the DHS working with "other Federal partners", in a process that "includes input from public and private sector CIKR community partners." Next comes prioritization, in which "DHS, in collaboration with other CIKR community partners and, in particular, DOS, prioritized the National Critical Foreign Dependencies List based on factors such as the overall criticality of the CIKR to the United States and the willingness and capability of foreign partners to engage in collaborative risk management activities.
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PRR-1 dome, 2019 The Philippine Research Reactor-1 was built under the Atoms for Peace nuclear research exchange program of the United States. The reactor which had its first criticality in August 26, 1963, was built by U.S. firm General Atomics and was originally a 1 MW MTR-type open pool general-purpose reactor. It was successfully operated from 1964-1984 and was utilized for training and research in nuclear science as well as for isotope production. In 1984, the Philippine Atomic Energy Commission (PAEC; then name of the Philippine Nuclear Research Institute (PNRI) decided to convert and upgrade the reactor into a 3 MW TRIGA Mark III reactor.
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Museum Tower (Dallas), Dallas, completed January 2013 Scott Johnson (born February 1, 1951) is an American architect. Educated at Stanford University, the University of California at Berkeley and the Harvard Graduate School of Design, Johnson has travelled widely and, in his early years, worked in a number of seminal firms. He is the co-founder and Design Partner of Johnson Fain, an international architecture, planning and interior design firm located in Los Angeles. Johnson is the author of several books, the most recent including Performative Skyscraper Tall Building Design Now, The Big Idea: Criticality & Practice in Contemporary Architecture and Tall Building: Imagining the Skyscraper.
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Slotin, who was leaving Los Alamos, was showing the technique to Alvin C. Graves, who would use it in a final test before the Operation Crossroads nuclear tests scheduled a month later at Bikini Atoll. It required the operator to place two half-spheres of beryllium (a neutron reflector) around the core to be tested and manually lower the top reflector over the core using a thumb hole on the top. As the reflectors were manually moved closer and farther away from each other, scintillation counters measured the relative activity from the core. The experimenter needed to maintain a slight separation between the reflector halves in order to stay below criticality.
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Temperature is also a factor. Calculations can be performed to determine the conditions needed for a critical state, mass, geometry, concentration etc. Where fissile materials are handled in civil and military installations, specially trained personnel are employed to carry out such calculations, and to ensure that all reasonably practicable measures are used to prevent criticality accidents, during both planned normal operations and any potential process upset conditions that cannot be dismissed on the basis of negligible likelihoods (reasonably foreseeable accidents). The assembly of a critical mass establishes a nuclear chain reaction, resulting in an exponential rate of change in the neutron population over space and time leading to an increase in neutron flux.
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As of June 2019, Canadian reactors had produced 2.9 million spent fuel bundles or around 52,000 tonnes of high-level waste, the second largest amount in the world behind the USA. This number could grow to 5.5 million bundles (103,000 tonnes) at the end of the planned life of the current reactors fleet. Spent fuel is stored at each reactor sites either in fuel pools (58% of the total) or dry cask storage (42%) when it is cool enough. Although more spent fuel is produced by CANDU reactors, dry storage costs for a given electricity production are comparable with costs for PWR reactors because the spent fuel is more easily handled (no fuel criticality).
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The Soviet submarine K-27 was scuttled in Stepovogo Bay with its two reactors filled with spent nuclear fuel. At a seminar in February 2012 it was revealed that the reactors on board the submarine could re-achieve criticality and explode (a buildup of heat leading to a steam explosion vs. nuclear). The catalogue of waste dumped at sea by the Soviets, according to documents seen by Bellona, includes some 17,000 containers of radioactive waste, 19 ships containing radioactive waste, 14 nuclear reactors, including five that still contain spent nuclear fuel; 735 other pieces of radioactively contaminated heavy machinery, and the K-27 nuclear submarine with its two reactors loaded with nuclear fuel.
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Schreiber with a Project Rover poster in 1959 After the war, Schreiber remained at Los Alamos, where he became a group leader in the Weapon (W) Division. His first assignment was to ready bombs for the Operation Crossroads nuclear tests at Bikini Atoll in the Pacific. During the preparations, he witnessed the accident in which Louis Slotin was exposed to a fatal dose of neutron radiation when a screwdriver Slotin was using during a criticality experiment with one of the plutonium pits for Operation Crossroads slipped and the core went critical. Slotin would die from radiation poisoning nine days later but his quick reaction saved the lives of Schreiber and the others in the room (see also: demon core).
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The sphere of plutonium surrounded by neutron-reflecting tungsten carbide blocks in a re- enactment of Daghlian's 1945 experiment During an experiment on August 21, 1945, Daghlian was attempting to build a neutron reflector manually by stacking a set of tungsten carbide bricks in an incremental fashion around a plutonium core. The purpose of the neutron reflector was to reduce the mass required for the plutonium core to attain criticality. He was moving the final brick over the assembly, but neutron counters alerted Daghlian to the fact that the addition of that brick would render the system supercritical. As he withdrew his hand, he inadvertently dropped the brick onto the center of the assembly.
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It is difficult to quantify the risk in a system, due to the stochastic nature of the events. However, it is possible to use other sources of information, such as gathered intelligence, economic and social drivers and data mining to assess the potential weaknesses and entry points of a system, along with the scale of consequences related to a breach in that system. Tools being developed for this purpose by the National Center for Food Protection and Defense include Focused Integration of Data for Early Signals (FIDES) and Criticality Spatial Analysis (CRISTAL). Food industry stakeholders can perform a vulnerability assessment to understand the vulnerabilities of their system, the consequences of an event and the potential threats and agents.
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Ling Ao phase I has two nuclear reactors, 950 MWe PWRs Ling Ao I-1 and I-2, based on the French 900 MWe three cooling loop design (M310), which started commercial operation in 2002 and 2003. The planned investment sum for phase I was ca 4 billion USD. In a Phase II development two CPR-1000 reactors, Ling Ao II-1 and II-2 (alternatively, units 3 and 4), were constructed in conjunction with Areva, based on the French three cooling loop design. Ling Ao II-1, China’s first domestic CPR-1000 nuclear power plant, was first connected to the grid on 15 July 2010, having started criticality testing on 11 June 2010.
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Worst-case circuit analysis (WCCA or WCA) is a cost-effective means of screening a design to ensure with a high degree of confidence that potential defects and deficiencies are identified and eliminated prior to and during test, production, and delivery. It is a quantitative assessment of the equipment performance, accounting for manufacturing, environmental and aging effects. In addition to a circuit analysis, a WCCA often includes stress and derating analysis, failure modes and effects criticality (FMECA) and reliability prediction (MTBF). The specific objective is to verify that the design is robust enough to provide operation which meets the system performance specification over design life under worst-case conditions and tolerances (initial, aging, radiation, temperature, etc.).
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Boric-acid was poured into the reactor in an attempt to stop the fission-reactions. No significant change in temperature or pressure was found by TEPCO, so there was no sign of large-scale criticality. The reactor-cooling was continued, but TEPCO would examine the situation at reactor 1 and 3 also.NHK-world (2 November 2011) TEPCO: Reactor may have gone critical The Mainichi Daily News (2 November 2011) TEPCO finds sign of fresh nuclear fission at Fukushima reactor Businessweek (2 November 2011) Professor Koji Okamoto of the University of Tokyo Graduate School made the comment that localized and temporary fission might still happen, and that the melted fuel could undergo fission, but the fuel was probably scattered around.
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In physics, Hamilton's principle is William Rowan Hamilton's formulation of the principle of stationary action. (See that article for historical formulations.) It states that the dynamics of a physical system are determined by a variational problem for a functional based on a single function, the Lagrangian, which contains all physical information concerning the system and the forces acting on it. The variational problem is equivalent to and allows for the derivation of the differential equations of motion of the physical system. Although formulated originally for classical mechanics, Hamilton's principle also applies to classical fields such as the electromagnetic and gravitational fields, and plays an important role in quantum mechanics, quantum field theory and criticality theories.
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However, when Kraft retired in 1982, former Apollo flight director Gerry Griffin was offered the position instead. In 1985, Lunney decided to leave NASA, feeling that the Space Shuttle program had worn him out physically and mentally and that he was ready for a new type of challenge. Although he had retired from NASA the year before, he was called to testify before the U.S. House Committee on Science and Technology in the aftermath of the Challenger accident. While still manager of the shuttle program, he had signed the "Criticality 1" waiver that allowed Challenger to launch even though the joints of its solid rocket boosters had recently been redefined as non-redundant systems.
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The technician can collect data samples from a number of machines, then download the data into a computer where the analyst (and sometimes artificial intelligence) can examine the data for changes indicative of malfunctions and impending failures. For larger, more critical machines where safety implications, production interruptions (so-called "downtime"), replacement parts, and other costs of failure can be appreciable (determined by the criticality index), a permanent monitoring system is typically employed rather than relying on periodic handheld data collection. However, the diagnostic methods and tools available from either approach are generally the same. Recently also on-line condition monitoring systems have been applied to heavy process industries such as pulp, paper, mining, petrochemical and power generation.
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The time between absorbing the neutron and undergoing fission is measured in nanoseconds. Szilard had noted that this reaction leaves behind fission products that may also release neutrons, but do so over much longer periods, from microseconds to as long as minutes. In a slow reaction like the one in a pile where the fission products build up, these neutrons account for about three percent of the total neutron flux. Fermi argued that by using the delayed neutrons, and by carefully controlling the reaction rates as the power is ramped up, a pile can reach criticality at fission rates slightly below that of a chain reaction relying solely on the prompt neutrons from the fission reactions.
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Fermi divided the square of the radius of the pile by the intensity of the radioactivity to obtain a metric that counted down to one as the pile approached criticality. At the 15th layer, it was 390; at the 19th it was 320; at the 25th it was 270 and by the 36th it was only 149. The original design was for a spherical pile, but as work proceeded, it became clear that this would not be necessary. The new graphite was purer, and of very pure metallic uranium began to arrive from the Ames Project at Iowa State University, where a team under Frank Spedding had developed a new process to produce uranium metal.
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Re-creation of Slotin's experiment with the "demon core" The occupational health studies of the Los Alamos National Laboratory and surrounding communities show elevated levels of certain disease rates among workers. A plutonium core for a nuclear weapon, nicknamed the "Demon Core" was involved in two accidents at LANL in 1945 and 1946, leading to the acute radiation poisoning and later the deaths of scientists Harry Daghlian and Louis Slotin. The first criticality incident occurred on August 21, 1945 when physicist Harry Daghlian accidentally dropped the core, causing a burst of neutron radiation that contaminated him and a security guard, Private Robert J. Hemmerly. The second incident caused the death of physicist, Louis Slotin, and contaminated seven other employees.
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The equivalence of power laws with a particular scaling exponent can have a deeper origin in the dynamical processes that generate the power-law relation. In physics, for example, phase transitions in thermodynamic systems are associated with the emergence of power-law distributions of certain quantities, whose exponents are referred to as the critical exponents of the system. Diverse systems with the same critical exponents—that is, which display identical scaling behaviour as they approach criticality—can be shown, via renormalization group theory, to share the same fundamental dynamics. For instance, the behavior of water and CO2 at their boiling points fall in the same universality class because they have identical critical exponents.
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Important standard features that make MCNP very versatile and easy to use include a powerful general source, criticality source, and surface source; both geometry and output tally plotters; a rich collection of variance reduction techniques; a flexible tally structure; and an extensive collection of cross-section data. MCNP contains numerous flexible tallies: surface current & flux, volume flux (track length), point or ring detectors, particle heating, fission heating, pulse height tally for energy or charge deposition, mesh tallies, and radiography tallies. The key value MCNP provides is a predictive capability that can replace expensive or impossible- to-perform experiments. It is often used to design large-scale measurements providing a significant time and cost savings to the community.
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Testing of nuclear weapons on live hogs at skin-searing distances, the Priscilla Test, and U.S. military troops at safer ranges are also featured. The film closes by highlighting anti-nuclear protest activities directed at the Diablo Canyon Power Plant on the California coast in the USA. The protesters contend, and the movie supports, the assertion that the protests were responsible for delaying the licensing of the Diablo Canyon Power Plant and, as a result of the delay, the uncovering of serious construction errors was made public just before the plant went online and started producing power. Discovered by a 25-year-old engineer prior to initial criticality, earthquake supports for nuclear piping had been installed backwards.
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A matching-critical graph is a graph for which the removal of any vertex does not change the size of a maximum matching; by Gallai's characterization, the matching-critical graphs are exactly the graphs in which every connected component is factor-critical.. The complement graph of a critical graph is necessarily matching-critical, a fact that was used by Gallai to prove lower bounds on the number of vertices in a critical graph.. As cited by . Beyond graph theory, the concept of factor-criticality has been extended to matroids by defining a type of ear decomposition on matroids and defining a matroid to be factor-critical if it has an ear decomposition in which all ears are odd..
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H. Boussier, S. Delpech, V. Ghetta et Al. : The Molten Salt Reactor (MSR) in Generation IV: Overview and Perspectives, GIF SYMPOSIUM PROCEEDINGS/2012 ANNUAL REPORT, NEA No. 7141, pp95 Current concept designs include thermal spectrum reactors (eg IMSR) as well as fast spectrum reactors (eg MCSFR). The early thermal spectrum concepts and many current ones rely on nuclear fuel, perhaps uranium tetrafluoride (UF4) or thorium tetrafluoride (ThF4), dissolved in molten fluoride salt. The fluid would reach criticality by flowing into a core where graphite would serve as the moderator. Many current concepts rely on fuel that is dispersed in a graphite matrix with the molten salt providing low pressure, high temperature cooling.
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Dr. Rafi Muhammad Chaudhry with English physicist, Thomas Allibone, Naeem Syed (in middle) and his other students in 1964, Government College, Lahore In 1960, Chaudhry joined the Pakistan Atomic Energy Commission, where he engaged nuclear technology research. He was the first director of the Pakistan Institute of Nuclear Science and Technology (PINSTECH), and was instrumental in the installation of nuclear particle accelerator there. Chaudhry published 42 research papers while at PINSTECH, and due to the sensitivity of the work, the papers were highly classified. Chaudhry was an administrative and influential figure in the establishment of PARR-I reactor as well, as being part team that supervised the first reactor criticality at PINSTECH.
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Heavy water is used in certain types of nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238, which captures neutrons without fissioning. The CANDU reactor uses this design. Light water also acts as a moderator, but because light water absorbs more neutrons than heavy water, reactors using light water for a reactor moderator must use enriched uranium rather than natural uranium, otherwise criticality is impossible. A significant fraction of outdated power reactors, such as the RBMK reactors in the USSR, were constructed using normal water for cooling but graphite as a moderator.
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The heating of the core and shells stopped the criticality within seconds of its initiation, while Slotin's reaction prevented a recurrence and ended the accident. The position of Slotin's body over the apparatus also shielded the others from much of the neutron radiation, but he received a lethal dose of neutron and gamma radiation in under a second and died nine days later from acute radiation poisoning. The nearest person to Slotin, Graves, who was watching over Slotin's shoulder and was thus partially shielded by him, received a high but non-lethal radiation dose. Graves was hospitalized for several weeks with severe radiation poisoning and developed chronic neurological and vision problems as a result of the exposure.
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The nuclear power plant was jointly designed by the engineers of Pakistan Atomic Energy Commission and the Canada's General Electric to provide distinction and difference from the India's nuclear research reactors such as CIRUS and Dhruva reactors that uses the same CANDU technology. The decision-making factor that was taken under consideration to sell the CANDU technology to Pakistan by Canada was seen as maintaining a balance of power between India and Pakistan. In 1966, the civil engineering and construction started by the Montreal Engineering Co. which finished its construction in 1971. The nuclear power plant attained criticality on 1 August 1971, and commenced on producing full power generation on 2 October 1972.
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CANDU type reactors operating in Canada have the particularity of being able to use natural uranium as fuel because of their high neutron economy. Therefore, the costly fuel enrichment step required by the more prevalent light-water reactor types can be avoided. However this comes at the cost of heavy water usage which, for example, represented 11% ($1.5 billion) of the capital costs of the Darlington plant. The low uranium-235 density in natural uranium (0.7% 235U) compared with enriched uranium (3-5% 235U) implies that less fuel can be consumed before the fission rate drops too low to sustain criticality, explaining why fuel burn-up in CANDU reactors (7.5 to 9 GW.day/tonnes) is far lower than in PWR reactors (50 GW.d/t).
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Maintain data link, inertial navigation, tactical network, message routing, digital production/projection, calibration, fiber optics, micro-miniature module test and repair, computer-based, and peripheral computer systems; analyze equipment operation, establish computer and network configurations, and troubleshoot and repair computer-based equipment to the lowest replaceable unit; execute casualty control procedures, restoring operability for all assigned electronic equipment, recognizing mission criticality and redundancies within systems; perform administrative functions that include the updating of casualty reporting messages, technical manuals, equipment maintenance records, and managing test equipment calibration requirements; complete fiber optic and basic soldering repair, electrical safety checks, and test equipment calibration; and supervise personnel who complete maintenance, conduct tool, MAM, and test equipment inventories, logistics support, and operational verification testing of new systems or equipment.
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Maintain surface search, air search, and weather radar systems, radar video switchboards, synchros, Identification Friend or Foe (IFF) equipment, tactical air navigation equipment, including all associated cabling, cooling water and dry air systems; analyze equipment operation and align, troubleshoot, and repair equipment to the lowest replaceable unit; execute casualty control procedures, restoring operability for all assigned electronic equipment, recognizing mission criticality and redundancies within systems; perform administrative functions that include managing test equipment calibration requirements and the updating of casualty reporting messages, technical manuals, and equipment maintenance records; complete, fiber optic and basic soldering repair, electrical safety checks, and test equipment calibration; and supervise personnel who complete maintenance, conduct tool, MAM, and test equipment inventories, logistics support, and operational verification testing of new systems or equipment.
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With Giuseppe Longo and Maël Montévil, he wrote (January 2012) "No Entailing Laws, But Enablement in the Evolution of the Biosphere", which argued that evolution is not "law entailed" like physics. Kauffman's work is posted on Physics ArXiv, including "Beyond the Stalemate: Mind/Body, Quantum Mechanics, Free Will, Possible Panpsychism, Possible Solution to the Quantum Enigma" (October 2014) and "Quantum Criticality at the Origin of Life" (February 2015). Kauffman has contributed to the emerging field of cumulative technological evolution by introducing a mathematics of the adjacent possible. He has published over 350 articles and 6 books: The Origins of Order (1993), At Home in the Universe (1995), Investigations (2000), Reinventing the Sacred (2008), Humanity in a Creative Universe (2016), and A World Beyond Physics (2019).
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Construction was completed in 18-months, the SM-1 reactor achieved first criticality on 8 April 1957, and the plant was formally opened in a public ceremony on 29 April 1957. Designed as a small- scale, pressurized-water, commercial nuclear power plant the power output from the SM-1 was connected to the local electrical grid. Thus, the SM-1 and Fort Belvoir hold the distinction of delivering the first nuclear generated electricity for public use in America, coming online several months before the (much larger, $55 million) Shippingport Reactor (in December 1957.)The Bulletin of the Atomic Scientists, February 1958 (Vol.14, issue 2: page 94); "News Roundup: Shippingport Reactor Generates Power" prepared by Helen C. Allison; accessed 11 March 2012.
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The Brookhaven National Laboratory (BNL) Graphite Research Reactor was the first nuclear reactor to be constructed in the United States following World War II. Led by Lyle Benjamin Borst, the reactor construction began in 1947 and reached criticality for the first time on August 22, 1950. The reactor consisted of a , cube of graphite fueled by natural uranium. Its primary mission was applied nuclear research in medicine, biology, chemistry, physics and nuclear engineering. One of the most significant discoveries at this facility was the development of production of molybdenum-99/technetium-99m, used today in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope. The BNL Graphite Research Reactor was shut down in 1969 and fully decommissioned in 2012.
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India published about twice the number of papers on thorium as its nearest competitors, during each of the years from 2002 to 2006. The Indian nuclear establishment estimates that the country could produce 500 GWe for at least four centuries using just the country's economically extractable thorium reserves. , India's first Prototype Fast Breeder Reactor had been delayed – with first criticality expected in 2015 – and India continued to import thousands of tonnes of uranium from Russia, Kazakhstan, France, and Uzbekistan. The 2005 Indo–US Nuclear Deal and the NSG waiver, which ended more than three decades of international isolation of the Indian civil nuclear programme, have created many hitherto unexplored alternatives for the success of the three-stage nuclear power programme.
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In the Chernobyl disaster, the moderator was not responsible for the primary event. Instead, a massive power excursion during a mishandled test caused the catastrophic failure of the reactor vessel and a near-total loss of coolant supply. The result was that the fuel rods rapidly melted and flowed together while in an extremely high power state, causing a small portion of the core to reach a state of runaway prompt criticality and leading to a massive energy release, resulting in the explosion of the reactor core and the destruction of the reactor building. The massive energy release during the primary event superheated the graphite moderator, and the disruption of the reactor vessel and building allowed the superheated graphite to come into contact with atmospheric oxygen.
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The relevant statement in the epilog reads as follows: "Indeed, the Germans were the first physicists in the world, with their Leipzig pile L-IV, to achieve positive neutron production, in the first half of 1942." At the end of July of the same year, the group around Fermi also succeeded in the neutron increase within a reactor-like arrangement. In June 1942, some six months before the American Chicago Pile-1 achieved man-made criticality for the first time anywhere, Döpel's "Uran-Maschine" was destroyed by a chemical explosion introduced by oxygen,This was the first accident that disrupted a nuclear energy assembly; cf. Reinhard Steffler, Reaktorunfälle und die Handlungen der Feuerwehr: Leipzig, Tschernobyl und Fukushima – eine erste Analyse.
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Ricardo Miranda Zúñiga (born 1971 in San Francisco) is an American new media artist who approaches art as a social practice that establishes dialogue in public spaces. Themes such as immigration, discrimination, gentrification and the effects of globalization extend from his experience and observations into works that tactically engage viewers through populist metaphors while maintaining criticality. He has said, "I have always felt very strongly that for art to matter its need to be socially relevant and exist outside of the gallery and museum amongst people at large." Zúñiga has shown his works in New York City; Berlin; Madrid; Valencia,Linz, Austria; Quebec; St. Petersburg; Chile; Washington, D.C.; Miami; São Paulo; Mexico; Tennessee; Chicago; Madison, Wisconsin; Buffalo; Philadelphia; and numerous times in California, including in San Francisco.
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The Water Boiler group was headed by Donald W. Kerst from the University of Illinois, and the group designed and built the Water Boiler, which achieved its criticality in May 1944 under the control of Enrico Fermi, after one final addition of uranium enriched to 14% uranium 235. It was the world's third reactor but the first reactor to use enriched uranium as a fuel, using most of the world's supply at the time, and the first to use liquid nuclear fuel in the form of soluble uranium sulfate dissolved in water. Holloway studied the safety of the Little Boy bomb, particularly what would happen if the active material became immersed in water. He was also involved in experiments to measure the critical mass of plutonium.
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Two CANDU fuel bundles: each is about 50 cm in length and 10 cm in diameter, and can generate about of electricity during its time in a CANDU reactor Bruce Nuclear Generating Station, operating eight CANDU reactors, is the largest nuclear power plant in the world by net operating capacity Natural uranium is a mix of isotopes, mainly uranium-238, with 0.72% fissile uranium-235 by weight. A reactor aims for a steady rate of fission over time, where the neutrons released by fission cause an equal number of fissions in other fissile atoms. This balance is referred to as criticality. The neutrons released in these reactions are fairly energetic and don't readily react with (get "captured" by) the surrounding fissile material.
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The "demon core": re-creation of the configuration used in the fatal 1945 criticality accident with a sphere of plutonium surrounded by neutron- reflecting tungsten carbide blocks. Precision plutonium foundry mold, 1959 The pit, named after the hard core found in fruits such as peaches and apricots, is the core of an implosion nuclear weapon – the fissile material and any neutron reflector or tamper bonded to it. Some weapons tested during the 1950s used pits made with U-235 alone, or in composite with plutonium,"Restricted Data Declassification Decisions from 1945 until Present" – "Fact that plutonium and uranium may be bonded to each other in unspecified pits or weapons." but all-plutonium pits are the smallest in diameter and have been the standard since the early 1960s.
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Monte Carlo N-Particle Transport (MCNP) is a general-purpose, continuous- energy, generalized-geometry, time-dependent, Monte Carlo radiation transport code designed to track many particle types over broad ranges of energies and is developed by Los Alamos National Laboratory. Specific areas of application include, but are not limited to, radiation protection and dosimetry, radiation shielding, radiography, medical physics, nuclear criticality safety, detector design and analysis, nuclear oil well logging, accelerator target design, fission and fusion reactor design, decontamination and decommissioning. The code treats an arbitrary three-dimensional configuration of materials in geometric cells bounded by first- and second-degree surfaces and fourth-degree elliptical tori. Point-wise cross section data are typically used, although group-wise data also are available.
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It has been defined to mean the accidental melting of the core of a nuclear reactor, however, and is in common usage a reference to the core's either complete or partial collapse. A core meltdown accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. This differs from a fuel element failure, which is not caused by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exceeds its design limits.
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The criticality resulting in the end of life is an intrinsic biological property of an organism that is independent of stress factors and signifies a fundamental or absolute limit of human lifespan. Average and commonly accepted maximum lifespans correspond to the extremums of the body mass (1, 2) and mass normalized to height (3, 4) of men (1, 3) and women (2, 4). A theoretical study suggested the maximum human lifespan to be around 125 years using a modified stretched exponential function for human survival curves. The analysis of dynamics of the body mass in human population indicates extremums, which correspond to mean (70–75 years), the commonly accepted maximum (100–110 years) and maximum known (140–160 years) lifespan.
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In September, Fermi assembled his first nuclear "pile" or reactor, in an attempt to create a slow neutron-induced chain reaction in uranium, but the experiment failed to achieve criticality, due to lack of proper materials, or not enough of the proper materials which were available. Producing a fission chain reaction in natural uranium fuel was found to be far from trivial. Early nuclear reactors did not use isotopically enriched uranium, and in consequence they were required to use large quantities of highly purified graphite as neutron moderation materials. Use of ordinary water (as opposed to heavy water) in nuclear reactors requires enriched fuel — the partial separation and relative enrichment of the rare 235U isotope from the far more common 238U isotope.
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December 7, 2014. Bernstein's article-turned- book "Notes on Post-Conceptual Poetry" is a critical and ambivalent survey of language poetry, conceptual poetry and the art in their lineage. Bernstein's central argument is that there has been a shift from language poetry's death of the author to conceptual poetry's death of the writerly to post-conceptual poetry's death of reading. The Goldsmith aesthetic, along with that of postpostmodernism in general (Queer Theory, Speculative Realism, Metamodernism, Gaga Feminism, Alternative literature, New Sincerity), has brought a decline in incisive and dialectical criticality, an overemphasis on social networks, slapdash viral superstars, and a hyper-mediated institutionalization of affect through an unconscious structuralism that masks itself as a romantic return to sheer materiality and the great outdoors.
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EMMA is a proof-of-principle machine; the experience gained in building this machine will be useful for future muon accelerators (which could be used in neutrino factories), and also for proton and carbon ion particle accelerators, which have applications for cancer therapy. Non-scaling FFAGs are a good candidate for use in an accelerator-driven subcritical reactor system in which a non- critical fission core is driven to criticality by a small accelerator. Future electrical power generation could be influenced heavily by the use power stations consisting of a sub-critical core containing a material such as thorium, and a small accelerator capable of providing extra neutrons via a spallation target. EMMA was funded by the BASROC consortium, under the CONFORM umbrella.
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A graph is said to be -factor-critical if every subset of vertices has a perfect matching. Under this definition, a hypomatchable graph is 1-factor-critical.. Even more generally, a graph is -factor-critical if every subset of vertices has an -factor, that is, it is the vertex set of an -regular subgraph of the given graph. A critical graph (without qualification) is usually assumed to mean a graph for which removing each of its vertices reduces the number of colors it needs in a graph coloring. The concept of criticality has been used much more generally in graph theory to refer to graphs for which removing each possible vertex changes or does not change some relevant property of the graph.
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In the early 1960s, it started the design and construction of AVR at the Jülich Research Centre. First criticality was attained in 1966, and the AVR was in operation for more than 22 years. Despite the fuel feed and discharge system showed excellent availability, the AVR was shut down for political reasons in 1988. The AVR was designed to breed uranium-233 from thorium-232. Thorium-232 is over 100 times as abundant in the Earth's crust as uranium-235. In 1965, before the AVR started operation, a basic design for a commercial demonstration HTGR reactor using thorium was started, the THTR-300. The HTGR, rated at 300 MWe, synchronized with the grid in 1985. Six months later a fuel pebble became lodged in the reactor core.
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While in a power reactor plenty of time exists for the decay of the isotopes in the isobar to form 133Cs, the 133Cs thus formed can then be activated to form 134Cs only if the time between the start and the end of the criticality is long. According to Jiri Hala's textbook, the radioactivity in the fission product mixture in an atom bomb is mostly caused by short-lived isotopes such as iodine-131 and barium-140. After about four months, cerium-141, zirconium-95/niobium-95, and strontium-89 represent the largest share of radioactive material. After two to three years, cerium-144/praseodymium-144, ruthenium-106/rhodium-106, and promethium-147 are responsible for the bulk of the radioactivity.
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Criticality accidents have occurred in the past, some of them with lethal consequences. Careless handling of tungsten carbide bricks around a 6.2 kg plutonium sphere resulted in a fatal dose of radiation at Los Alamos on August 21, 1945, when scientist Harry Daghlian received a dose estimated to be 5.1 sievert (510 rems) and died 25 days later. Nine months later, another Los Alamos scientist, Louis Slotin, died from a similar accident involving a beryllium reflector and the same plutonium core (the so-called "demon core") that had previously claimed the life of Daghlian. In December 1958, during a process of purifying plutonium at Los Alamos, a critical mass was formed in a mixing vessel, which resulted in the death of a chemical operator named Cecil Kelley.
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For example, while one of a set of collocated MSL OS may be configured to affix the character string "SECRET" to all output, that OS has no understanding of how the data compares in sensitivity and criticality to the data processed by its peer OS that affixes the string "UNCLASSIFIED" to all of its output. Operating across two or more security levels then, must use methods extraneous to the purview of the MSL "operating systems" per se, and needing human intervention, termed "manual review". For example, an independent monitor (not in Brinch Hansen's sense of the term) may be provided to support migration of data among multiple MSL peers (e.g., copying a data file from the UNCLASSIFIED peer to the SECRET peer).
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"History of Argonne Reactor Operations", p. 6. With Albert Wattenberg, Lichtenberger designed and tested the first pressurized heavy-water reactor, Chicago Pile-3, and with Walter Zinn performed a number of other reactor experiments at the Argonne National Laboratory, including the first breeder reactor, EBR-1, and the boiling water reactor BORAX-III, the first reactor to supply power to an entire city (Arco, Idaho, in 1955 with 500 kW). He became director of the Idaho Division of the Metallurgical Laboratory and Argonne National Laboratory, where new reactors were tested. In 1954, Lichtenberger was also in charge of experiments at the proving ground in Idaho in which experimental reactors were systematically taken beyond criticality and caused to explode by manipulation of the control rods.
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Following the 2011 Fukushima nuclear disaster, Duncan remained optimistic about the prospect of nuclear power in Australia. In 2013, he wrote that "if the economics for electricity generation is impacted by a carbon tax or a compulsory carbon capture and sequestration, then nuclear generation will be economically competitive." At a conference entitled "Nuclear Power for Australia?" held by ATSE in July of that year, he argued that if Australia were to aspire to produce electricity with nuclear power plants, a new Commonwealth agency 'inspectorate' with regulatory control over the choice of technology, siting, construction and operation should be established by 2016. He proposed the working title Nuclear Installations Regulator for Australia (NIRA) and presented a detailed timeline of potential milestones to achieve between 2013 and criticality for the first reactor in 2030.
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Scheduling MSE in an optimal way is a complex multi- faceted problem. Each "observing matrix" (one observation made at a single telescope pointing and suite of associated fibre positions) targets spectra from more than 4300 fibres pointing at objects selected from a few simultaneous surveys as well as calibration targets and targets of opportunity, and with spectrographs and indeed arms of spectrographs configured differently in each observing matrix. Objects are selected to be included in any observing matrix on the bases of science priority, time criticality, observing conditions, source brightness, sky brightness, calibration needs, and fibre yield (the fraction of fibre tips that can be placed on useful science objects). Software tools are being defined to automate steps in the operations sequence, going from survey definition to the delivery of science data.
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Therefore, the reaction will increase slowly, with a long time constant. This is slow enough to allow the reaction to be controlled with electromechanical control systems such as control rods, and as such all nuclear reactors are designed to operate in the delayed-criticality regime. In contrast, a critical assembly is said to be prompt-critical if it is critical (k=1) without any contribution from delayed neutrons and prompt-supercritical if it is supercritical (the fission rate growing exponentially, k>1) without any contribution from delayed neutrons. In this case the time between successive generations of the reaction, T, is only limited by the fission rate from the prompt neutrons, and the increase in the reaction will be extremely rapid, causing a rapid release of energy within a few milliseconds.
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The role or size of the third party is not as important as the nature of the relationship, the criticality of its activities, the level of access it has to sensitive data or property, and a company's accountability for inappropriate actions of its third parties. A cleaning company with access to a CEO's filing cabinet represents a different but still significant risk relative to a supplier who provides a critical component to the production line. A non-critical service provider – such as an air-conditioning contractor – operating in a country with low corruption risk may erroneously be considered a low risk. However, if that contractor has poor cyber-security and is able to submit invoices to a customer electronically across the customer's firewall, this may represent a high cyber risk to the customer company.
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In a nuclear reactor, criticality is achieved when the rate of neutron production is equal to the rate of neutron losses, including both neutron absorption and neutron leakage. When a uranium-235 atom undergoes fission, it releases an average of 2.4 neutrons. In the simplest case of an unreflected, homogeneous, spherical reactor, the critical radius was calculated to be approximately: ,}} where M is the average distance that a neutron travels before it is absorbed, and k is the average neutron multiplication factor. The neutrons in succeeding reactions will be amplified by a factor k, the second generation of fission events will produce k2, the third k3 and so on. In order for a self-sustaining nuclear chain reaction to occur, k must be at least 3 or 4 percent greater than 1.
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For evacuating Power from the gas based 726.6 MW power Project Generators, a trunk transmission line is being developed by another Special Purpose Vehicle (SPV), jointly promoted by Power Grid Corporation Ltd., OTPC and the North Eastern Region (NER) states. Inter- state and intrastate sub-transmission system and the distribution system within NER states shall be developed by Power Grid Corporation as the Central Transmission Utility (CTU) The Transmission Project was initially envisaged to be domiciled in a separate SPV, North-East Power Transmission Company Limited ("NEPTC") and developed through a BOOT operator. However given the criticality of timely completion of the Transmission System to the operations of the Generation Plant, a decision was taken to develop the transmission system as a component of the composite Project within OTPC.
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Since 1990, Egypt started to search for a new research reactor to replace the aging ETRR-1 and the Israeli press claimed that Egypt was cooperating with Pakistan, Iraq and Argentina to build a plutonium- producing reactor for nuclear weapons. Finally, Egypt announced international tender and among the bidders were the Canadian Atomic Energy of Canada Limited, the French Framatome and the Argentinian INVAP. On September 1992, a contract was signed between INVAP and the Egyptian Atomic Energy Authority (AEA) and a branch office of INVAP in Nasr City was established to oversee the project with the construction works began in 1993 jointly by Argentina and Egypt. On November 1997, ETRR-2 achieved initial criticality, and was inaugurated by the former Egyptian president Hosni Mubarak and the Argentine president Carlos Menem on February 1998.
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Since power in a reactor is proportional to the number of neutrons present in the nuclear fuel material (material in which fission can occur), the power produced by such a subcritical core will also be proportional to the subcritical multiplication factor and the external source strength. As a measurement technique, subcritical multiplication was used during the Manhattan Project in early experiments to determine the minimum critical masses of 235U and of 239Pu. It is still used today to calibrate the controls for nuclear reactors during startup, as many effects (discussed in the following sections) can change the required control settings to achieve criticality in a reactor. As a power-generating technique, subcritical multiplication allows generation of nuclear power for fission where a critical assembly is undesirable for safety or other reasons.
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On 8 February 1959, reactor No. 2 achieved initial criticality, while reactor No 1 achieved this milestone on 3 April 1959. Two shipboard accidents occurred during Tritons post-launch fitting-out. On 2 October 1958, prior to the nuclear reactor fuel being installed, a steam valve failed during testing, causing a large cloud of steam that filled the number two reactor compartment, and on 7 April 1959, a fire broke out during the testing of a deep-fat fryer and spread from the galley into the ventilation lines of the crew's mess. Both incidents, neither nuclear related, were quickly handled by ship personnel, with Lt. Commander Leslie D. Kelly, the prospective chief engineering officer, being awarded the Navy and Marine Corps Medal for his quick action during the incident on 2 October.
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Contrary to NASA regulations, the Marshall Center did not report this problem to senior management at NASA, but opted to keep the problem within their reporting channels with Thiokol. Even after the O-rings were redesignated as "Criticality 1"—meaning that their failure would result in the destruction of the Orbiter, no one at Marshall suggested that the shuttles be grounded until the flaw could be fixed. After the 1984 launch of STS-41-D, flown by Discovery, the first occurrence of hot gas "blow-by" was discovered beyond the primary O-ring. In the post-flight analysis, Thiokol engineers found that the amount of blow-by was relatively small and had not impinged upon the secondary O-ring, and concluded that for future flights, the damage was an acceptable risk.
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This process only occurs with higher-energy neutrons than would be found in a moderated reactor, so a conventional reactor only produces small amounts of Pu when the neutron is captured within the fuel mass before it is moderated. More typically, special reactors are used that are designed specifically for the breeding of Pu-239. The simplest way to achieve this is to further enrich the original U-235 fuel well beyond what is needed for use in a moderated reactor, to the point where the U-235 maintains criticality even with the fast neutrons. The extra fast neutrons escaping the fuel load can then be used to breed fuel in a U-238 assembly surrounding the reactor core, most commonly taken from the stocks of depleted uranium.
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The demon core was intended to be used in the Operation Crossroads nuclear tests, but after the criticality accident, time was needed for its radioactivity to decline and for it to be re-evaluated for the effects of the fission products it held, some of which could be very poisonous to the desired level of fission. The next two cores were shipped for use in Able and Baker, and the demon core was scheduled to be shipped later for the third test of the series, provisionally named Charlie, but that test was cancelled due to the unexpected level of radioactivity resulting from the underwater Baker test and the inability to decontaminate the target warships. The core was later melted down and the material recycled for use in other cores.
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This is embodied in the initial part of the RCM process which is to identify the operating context of the machinery, and write a Failure Mode Effects and Criticality Analysis (FMECA). The second part of the analysis is to apply the "RCM logic", which helps determine the appropriate maintenance tasks for the identified failure modes in the FMECA. Once the logic is complete for all elements in the FMECA, the resulting list of maintenance is "packaged", so that the periodicities of the tasks are rationalised to be called up in work packages; it is important not to destroy the applicability of maintenance in this phase. Lastly, RCM is kept live throughout the "in-service" life of machinery, where the effectiveness of the maintenance is kept under constant review and adjusted in light of the experience gained.
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Nuclear data represents measured (or evaluated) probabilities of various physical interactions involving the nuclei of atoms. It is used to understand the nature of such interactions by providing the fundamental input to many models and simulations, such as fission and fusion reactor calculations, shielding and radiation protection calculations, criticality safety, nuclear weapons, nuclear physics research, medical radiotherapy, radioisotope therapy and diagnostics, particle accelerator design and operations, geological and environmental work, radioactive waste disposal calculations, and space travel calculations It groups all experimental data relevant for nuclear physics and nuclear applications. It includes a large number of physical quantities, like scattering and reaction cross sections (which are generally functions of energy and angle), nuclear structure and nuclear decay parameters, etc. It can involve neutrons, protons, deuterons, alpha particles, and virtually all nuclear isotopes which can be handled in a laboratory.
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While 235U is sensitive to these neutrons, the reaction rate is greatly improved if the neutrons are slowed from their original relativistic speeds to much lower energies, the so-called thermal neutron velocities. In a mass of pure natural uranium, the number and energy of the neutrons being released through natural decay are too low to cause appreciable fission events in the few 235U atoms present. In order to increase the rate of neutron capture to the point where a chain reaction can occur, known as criticality, the system has to be modified. In most cases, the fuel mass is separated into a large number of smaller fuel pellets and then surrounded by some form of neutron moderator that will slow the neutrons, thereby increasing the chance that the neutrons will cause fission in 235U in other pellets.
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Stochastic (partial) differential equations (SDEs) are the foundation for models of everything in nature above the scale of quantum degeneracy and coherence and are essentially Witten-type TQFTs. All SDEs possess topological or BRST supersymmetry, \delta, and in the operator representation of stochastic dynamics is the exterior derivative, which is naturally commutative with the stochastic evolution operator, defined as the pullback induced by phase space diffeomorphisms as specified by the SDEs and averaged over noise configurations. This supersymmetry preserves the continuity of phase space by continuous flows, and the phenomenon of supersymmetric spontaneous breakdown by a global non- supersymmetric ground state encompasses such well-established physical concepts as chaos, turbulence, 1/f and crackling noises, self-organized criticality etc. The topological sector of the theory for any SDE can be recognized as a Witten-type TQFT.
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Basic tools of econophysics are probabilistic and statistical methods often taken from statistical physics. Physics models that have been applied in economics include the kinetic theory of gas (called the kinetic exchange models of markets ), percolation models, chaotic models developed to study cardiac arrest, and models with self-organizing criticality as well as other models developed for earthquake prediction. Moreover, there have been attempts to use the mathematical theory of complexity and information theory, as developed by many scientists among whom are Murray Gell-Mann and Claude E. Shannon, respectively. For potential games, it has been shown that an emergence- producing equilibrium based on information via Shannon information entropy produces the same equilibrium measure (Gibbs measure from statistical mechanics) as a stochastic dynamical equation, both of which are based on bounded rationality models used by economists.
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During the regime of president Marcos Pérez Jiménez, Venezuela became member of the International Atomic Energy Agency after purchasing the RV-1 reactor from General Electric in 1956. The project was supported by the administration of United States President Dwight D. Eisenhower, to help promote the Atoms for Peace program, with the United States donating US$300,000 for the construction of the reactor. The reactor was constructed in the grounds of the Venezuelan Institute of Neurology and Brain Research (IVNIC, now known as IVIC - Venezuelan Institute for Scientific Research) under the supervision of Humberto Fernández-Morán; he never saw the project finished, as he went into exile after the Pérez Jiménez regime fell in 1958. The reactor reached criticality in 1960 and was used for several decades to perform physics research, radiochemistry, production of radioisotopes and as neutron source.
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It can be used as a solvent (in the purely chemical sense rather than the solvent extraction sense) to dissolve an extractant which is a solid and so render it suitable for use in a liquid–liquid extraction process. In other cases such as PUREX nuclear reprocessing the diluent (kerosene) is used to reduce the maximum metal loading which the organic layer can reach. If the organic layer was to acquire too much metal then a solid metal complex might form, or more worryingly in a nuclear process the potential for a criticality accident if the fissile metal concentration in the organic phase becomes too high. Water is probably the most common and familiar diluent, but many substances, such as oils, do not dissolve well in water and therefore require different diluents to be diluted effectively without separating into parts.
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Scientific American The l'Aquila Verdict. A Judgment Not Against Science, but Against A Failure of Science Communication During the trial, other scientists attacked the scientific conduct of the commission. Professor Francesco Giovanni Maria Stoppa, a member of the commission until 2003, said: "They should have given information proportional to our knowledge, which in 2009 spotlighted a criticality in L'Aquila. Under those conditions, there were 5–6 days before the quake to give information, and this doesn't mean forecasting earthquakes."«Avrebbero dovuto dare una informazione proporzionata alle nostre conoscenze, che nel 2009 mettevano in luce una criticità all'Aquila. Nelle condizioni che c'erano 5 – 6 giorni prima del terremoto bisognava dare informazioni e questo non-vuol dire prevedere i terremoti» Il Capoluogo In protest over the prison sentences handed to his seven colleagues, Luciano Maiani, the head of Italy's disaster body, resigned.
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135Xe buildup in a reactor core makes it extremely dangerous to operate the reactor a few hours after it has been shut down. Because the 135Xe absorbs neutrons strongly, starting a reactor in a high-Xe condition requires pulling the control rods out of the core much farther than normal. However, if the reactor does achieve criticality, then the neutron flux in the core becomes high and 135Xe is destroyed rapidly—this has the same effect as very rapidly removing a great length of control rod from the core, and can cause the reaction to grow too rapidly or even become prompt critical. 135Xe played a large part in the Chernobyl accident: about eight hours after a scheduled maintenance shutdown, workers tried to bring the reactor to a zero power critical condition to test a control circuit.
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Fisher is one of the leading figures in condensed matter physics, and has made important contributions to many areas in condensed matter physics. Some of his most important works have been in the theories of quantum phase transitions, in particular superconductor-insulator transitions (with Daniel Fisher, Steven Girvin and others) and deconfined quantum criticality (with Subir Sachdev, T. Senthil, Ashvin Vishwanath and Leon Balents). He has also made important contributions to superconductivity, in particular, introducing vortex-glass superconductivity as a possible new phase of matter and using bosonic particle-vortex dualities to describe the properties of superconductors (with Dung-Hai Lee). He has also made significant advances in the transport and other aspects of the physics of Luttinger liquids (with Charles Kane) and other one-dimensional problems in condensed matter such as the edges of quantum Hall states.
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Conversely, reduction beyond the size of the W54 means that linear implosion designs must be employed and neutron reflectors dispensed with ("bare core"), so a much larger mass of fissile material is required and explosive yield is reduced dramatically. Taylor's figures represent the minimum size and mass to sustain a prompt criticality but the duration without tamper or neutron reflection would be short. The slope of exponential growth, estimated number of fissions, and specific fissile material are not recorded. Neptunium-236 is fissile and possesses the smallest and lightest critical mass, but isolation of the specific radionuclide makes it an impractical choice. Several other novel fissile materials are known, but U-235 and Pu-239 are the only practical options although two US tests using U-233 (critical mass some 32% less than U235) have taken place.
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The S1W was a pressurized water reactor that utilized water as the coolant and neutron moderator in its primary system, and enriched Uranium-235 in its fuel elements. The S1W reactor reached criticality on March 30, 1953. In May of that year, it began power operations, performing a 100-hour run that simulated a submerged voyage from the east coast of the United States to Ireland. This test run clearly demonstrated the revolutionary impact that nuclear propulsion would have upon the submarine, which prior to that time was greatly limited in its ability to conduct continuous underwater operations by battery life and by the oxygen requirement of diesel propulsion systems. The heated, pressurized water of the S1W reactor power plant was circulated through heat exchangers in order to generate high pressure saturated steam in a separate water loop.
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This > is because it needs to maintain a certain sense of criticality and > experimental research among a minority, but must take care to channel this > activity into narrowly compartmentalized utilitarian disciplines, dismissing > all comprehensive critique and research. In the domain of culture, the > bourgeoisie strives to divert the taste for the new, which has become > dangerous for it, toward certain degraded forms of novelty that are harmless > and confused. [...] The people within avant-garde tendencies who > distinguished themselves are generally accepted on an individual basis, at > the price of vital renunciations: the fundamental point of debate is always > the renunciation of comprehensive demands, and the acceptance of a > fragmentary work, susceptible to multiple interpretations. This is what > makes the very term avant-garde, which in the end is always defined and > manipulated by the bourgeoisie, somewhat suspicious and ridiculous.
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On the day of the accident, the mixing tank was supposed to contain what nuclear chemists call a "lean" concentration of dissolved plutonium (≤0.1 g of plutonium per liter of solution) in a bath of highly corrosive nitric acid and a caustic, stabilized, aqueous, organic emulsion. However, as a result of at least two "improper transfers" of plutonium waste to the tank (the sources of which were never determined, about which Kelley had neither reason to suspect nor ability to observe), the concentration of plutonium in the mixing tank on this particular occasion was nearly 200 times higher. Worse, it was also distributed unevenly: the upper layer of solution had especially high concentrations and contained a total of over 3 kg of plutonium, which was already close to criticality before Kelley acted. When Kelley switched on the mixer, a vortex began to form.
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It also allows for a higher ratio of UF4 to helium, which in the terrestrial version would be kept just high enough to ensure criticality in order to increase the efficiency of direct conversion. The terrestrial version is designed for a vapor core inlet temperature of about 1,500 K and exit temperature of 2,500 K and a UF4 to helium ratio of around 20% to 60%. It is thought that the outlet temperature could be raised to that of the 8,000 K to 15,000 K range where the exhaust would be a fission-generated non-equilibrium electron gas, which would be of much more importance for a rocket design. A terrestrial version of the VCR's flow schematic can be found in reference 2 and in the summary of non-classical nuclear systems in the second external link.
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USS San Antonio Maintain shore-based, ship-based, portable communications equipment, and portable Mechatronic equipment, including all associated cabling, computer, multiplexing, motor, switching, cryptographic, recording, cooling water and dry air systems; analyze equipment operation and align, troubleshoot using digital multimeters, oscilloscopes, thermal couples and repair equipment to the lowest replaceable unit; execute casualty control procedures, restoring operability for all assigned electronic equipment, recognizing mission criticality and redundancies within systems; perform administrative functions that include the updating of casualty reporting messages, technical manuals, equipment maintenance records, and managing test equipment calibration requirements;Motors and motor controls for satellite antennas, radar cooling motor control pumps mechanical knowledge of electrical motor characteristics brush and brushless, complete fiber optic and basic soldering repair, electrical safety checks, and test equipment calibration; and supervise personnel who complete maintenance, conduct tool, MAM, and test equipment inventories, logistics support, and operational verification testing of new systems or equipment.
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GSN Community Standard Safety Cases are becoming more popular on civil/commercial aircraft and Department of Defense (DoD) weapon systems as complexity and criticality increase. A paradigm shift is often necessary to accept Safety Cases as traditional system safety and software safety analysis and verification approaches and processes are not adequately structured to present an effective safety argument on some more modern architectures using modern development tools and formal methods. Some major programs in the US Department of Defense, such as the F-35 Vehicle Management System (VMS) are using Model Based System Engineering (MBSE) effectively on highly complex, software intensive and safety-critical airborne system functions, along with Goal Structuring Notation (GSN). Safety Assessments and more elaborate and comprehensive Safety Cases with GSN are effective so long as Refuting Arguments and much scrutiny using traditional hazard analyses and safety approaches are included and models used to depict system behavior.
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These nanoflares might themselves resemble very tiny flares, close one to each other, both in time and in space, effectively heating the corona and underlying many of the phenomena of solar magnetic activity. Episodic heating often observed in active regions, including major events such as flares and coronal mass ejections could be provoked by cascade effects, similar to those described by the mathematical theories of catastrophes. In the hypothesis that the solar corona is in a state of self-organized criticality, the stressing of the magnetic field should be enhanced until a small perturbation switches on many small instabilities, happening together as it occurs in avalanches. One of the experimental results often cited in supporting the nanoflare theory is the fact that the distribution of the number of flares observed in the hard X-rays is a function of their energy, following a power law with negative spectral index.
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The inspector general of the Department of Homeland Security (DHS) found that the list of terrorist target sites contained in the DHS "National Asset Database," the sites that are supposed to receive extra security in response to heightened terror alerts, included many sites “whose criticality is not readily apparent” and should not be included on the list. For example, the list included a beach at the end of a street, a popcorn factory, a doughnut shop, and a petting zoo. By July 2006, the list included 77,069 target sites. The inspector general's report found other wild discrepancies, for example, that the State of Indiana had 8,591 potential terrorist targets, 50% more targets than New York State with 5,687 targets, and more than twice as many as the State of California, which had only 3,212, even though New York and California are larger than Indiana and include more prominent American landmarks.
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Fission of uranium normally produces five known isotopes of the fission-product gas xenon; all five have been found trapped in the remnants of the natural reactor, in varying concentrations. The concentrations of xenon isotopes, found trapped in mineral formations 2 billion years later, make it possible to calculate the specific time intervals of reactor operation: approximately 30 minutes of criticality followed by 2 hours and 30 minutes of cooling down to complete a 3-hour cycle. A key factor that made the reaction possible was that, at the time the reactor went critical 1.7 billion years ago, the fissile isotope made up about 3.1% of the natural uranium, which is comparable to the amount used in some of today's reactors. (The remaining 96.9% was non-fissile .) Because has a shorter half-life than , and thus decays more rapidly, the current abundance of in natural uranium is about 0.70–0.72%.
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In the United States, where Fermi and Szilárd had both emigrated, the discovery of the nuclear chain reaction led to the creation of the first man-made reactor, the research reactor known as Chicago Pile-1, which achieved criticality on December 2, 1942. The reactor's development was part of the Manhattan Project, the Allied effort to create atomic bombs during World War II. It led to the building of larger single-purpose production reactors, such as the X-10 Pile, for the production of weapons-grade plutonium for use in the first nuclear weapons. The United States tested the first nuclear weapon in July 1945, the Trinity test, with the atomic bombings of Hiroshima and Nagasaki taking place one month later. The first light bulbs ever lit by electricity generated by nuclear power at EBR-1 at Argonne National Laboratory-West, December 20, 1951.
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This raised hopes that pure uranium would yield a suitable value of k. By December 1942, Zinn and Anderson had the new configuration ready at Stagg Field. Some long, wide and high, it contained of graphite and of uranium metal and uranium oxide. When the experiment was carried out on the afternoon of December 2, 1942, the reactor, known as Chicago Pile-1, reached criticality without incident. Since the reactor had no radiation shield, it was run at a maximum power of only 200 W, enough to power a light bulb, and ran for only three months. It was shut down on February 28, 1943, because the US Army did not want to risk an accident near densely populated downtown Chicago. The Army leased a of the Cook County Forest Preserves known as "Site A" to the Manhattan Project, and "the Country Club" to the hundred or so scientists, guards and others who worked there.
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Haroutune Krikor Daghlian Jr. (; May 4, 1921 – September 15, 1945) was an American physicist with the Manhattan Project, which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico, and died 25 days later from the resulting radiation poisoning. Herbert Lehr (left) and Harry Daghlian, Jr. (right), loading the assembled tamper plug containing the plutonium pit and initiator into a sedan for transport from the McDonald ranch house to the shot tower on July 13, 1945. Daghlian was irradiated as a result of a criticality accident that occurred when he accidentally dropped a tungsten carbide brick onto a 6.2 kg plutonium–gallium alloy bomb core. This core, subsequently nicknamed the "demon core", was later involved in the death of another physicist, Louis Slotin.
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Furthermore, both hydrophobicity and icephobicity can lead to quite complex phenomena, such as self-organized criticality-driven complexity as a result of hydrophobic interactions (during wetting of rough/heterogeneous surfaces or during polypeptide chain folding and looping) or ice crystallization (fractal snowflakes). Note that thermodynamically both the hydrophobic interactions and ice formation are driven by the minimization of the surface Gibbs energy, ΔG = ΔH − TΔS, where H, T, and S are the enthalpy, temperature, and entropy, respectively. This is because in the hydrophobic interactions large positive value of TΔS prevails over a small positive value of ΔH making spontaneous hydrophobic interaction energetically profitable. The so-called surface roughening transition governs the direction of ice crystal growth and occurs at the critical temperature, above which the entropic contribution into the Gibbs energy, TΔS, prevails over the enthalpic contribution, ΔH, thus making it more energetically profitable for the ice crystal to be rough rather than smooth.
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Reactivating the battleships would have required a wide range of battleship modernization improvements, according to the navy's program management office. At a minimum, these modernization improvements included command and control, communications, computers, and intelligence equipment; environmental protection (including ozone-depleting substances); a plastic-waste processor; pulper/shredder and wastewater alterations; firefighting/fire safety and women-at-sea alterations; a modernized sensor suite (air and surface search radar); and new combat and self-defense systems. The navy's program management office also identified other issues that would strongly discourage the Navy from reactivating and modernizing the battleships. For example, personnel needed to operate the battleships would have been extensive, and the skills needed might not have been available or easily reconstituted.The U.S. Navy reported in the April 1987 edition of All Hands that while battleships had larger crews than other vessels the level of training required and the criticality of that training were less than that required of a crew aboard an .
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The Shippingport Atomic Power Station was (according to the US Nuclear Regulatory Commission) the world's first full-scale atomic electric power plant devoted exclusively to peacetime uses.Though Obninsk Nuclear Power Plant was connected to the Moscow Grid in 1954 and was the first nuclear reactor that produced commercial electricity, it can still be considered a small scale station designed principally to carry out nuclear experiments. The first British Magnox reactor at Calder Hall was connected to the grid on 27 August 1956, its primary purpose was to produce plutonium for military uses.The Vallecitos Nuclear Center started producing electric power in October 1957, but it served as a test or pilot plant. It was located near the present-day Beaver Valley Nuclear Generating Station on the Ohio River in Beaver County, Pennsylvania, United States, about 25 miles (40 km) from Pittsburgh. The reactor reached criticality on December 2, 1957, and aside from stoppages for three core changes, it remained in operation until October 1982.
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Even in a subcritical assembly such as a shut-down reactor core, any stray neutron that happens to be present in the core (for example from spontaneous fission of the fuel, from radioactive decay of fission products, or from a neutron source) will trigger an exponentially decaying chain reaction. Although the chain reaction is not self-sustaining, it acts as a multiplier that increases the equilibrium number of neutrons in the core. This subcritical multiplication effect can be used in two ways: as a probe of how close a core is to criticality, and as a way to generate fission power without the risks associated with a critical mass. If k is the neutron multiplication factor of a subcritical core and S_0 is the number of neutrons coming per generation in the reactor from an external source, then at the instant when the neutron source is switched on, number of neutrons in the core will be S_0.
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Among other ideal characteristics, the ideal shape for any fissile substance to become supercritical is the shape of least surface area, a sphere. Although the plutonium-rich solution was not spherical, the vortex made it thicker in the center, and this, along with the corresponding increase in density and the neutron reflectivity of the aqueous layer surrounding it, caused the dissolved plutonium to reach and cross the criticality threshold in approximately one second: neutrons within the mixture began to bombard the nuclei of the solution's plutonium atoms with sufficient frequency to cause these atoms to break apart and release other neutrons in a sustained nuclear chain reaction lasting only 200 microseconds but releasing a huge burst of neutrons and gamma radiation. Such an uncontrolled release of nuclear energy is often referred to as an excursion. Within 3 seconds, the layers in the mixture had become dispersed, and no further excursions were possible.
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Crucially, however, the paper emphasized that the complexity observed emerged in a robust manner that did not depend on finely tuned details of the system: variable parameters in the model could be changed widely without affecting the emergence of critical behavior: hence, self- organized criticality. Thus, the key result of BTW's paper was its discovery of a mechanism by which the emergence of complexity from simple local interactions could be spontaneous--and therefore plausible as a source of natural complexity--rather than something that was only possible in artificial situations in which control parameters are tuned to precise critical values. The publication of this research sparked considerable interest from both theoreticians and experimentalists, producing some of the most cited papers in the scientific literature. Due to BTW's metaphorical visualization of their model as a "sandpile" on which new sand grains were being slowly sprinkled to cause "avalanches", much of the initial experimental work tended to focus on examining real avalanches in granular matter, the most famous and extensive such study probably being the Oslo ricepile experiment.
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Even a small increase of the mechanical strength of the ceramic body would lead to a reduction in the weight of the ceramic article with a deepreduction of the above pollution effects. Consequently, the set-up of manufacturing processes is very costly and time consuming and not yet optimal in terms of quality of the final piece. There is therefore a strong interest from the ceramic industry in the availability of tools capable of modelling and simulating: i) the powder compaction process and ii) the criticality of defects possibly present in the final piece after sintering. Recently, an EU IAPP research project has been financed with the aim of enhance mechanical modelling of ceramic forming in view of industrial applications. During cold powder compaction, a granular material is made cohesive through mechanical densification, a process for which modelling requires the description of the transition from a granular to a dense and even a fully dense state (Fig. 2). Fig. 3 The hardening process during hydrostatic powder compaction described with the Bigoni & Piccolroaz yield surface.
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April 19, 2009. First concrete for Sanmen 2 was poured on December 15, 2009. In June 2014, China First Heavy Industries completed the first domestically produced AP1000 reactor pressure vessel for the second AP1000 unit. The units were originally projected to begin operation in 2014 and 2015. In April 2015, a start date of 2016 was projected for both. One month later, the start date was put back to 2017. In January 2017 China National Nuclear Corporation (CNNC) announced that the final reactor coolant pump had been installed with start of operations still foreseen for 2017. , Sanmen 1 had completed pre-fuelling safety checks but was not expected to be connected to the grid until the fall of 2018 at the earliest. Hot testing of Sanmen 1 was completed in June 2017, and fuel loading started on April 25, 2018. It subsequently became the first AP1000 reactor in the world to achieve first criticality at 2:09 AM on June 21, 2018, and was connected to the grid on June 30, 2018.
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The project was approved by the National Development and Reform Commission in April 2006, and projected to cost 23 billion Renminbi for the first two units. The cost will be shared between the China Power Investment Corporation, the China General Nuclear Power Group and two Liaoning companies. Liaoning Hongyanhe Nuclear Power Co., Ltd., a joint venture, is managing the construction and will be the operator of the plant once it goes online. The operator is a 45–45–10 joint venture of China Power Investment Corporation (now State Power Investment Corporation), China General Nuclear Power Group and Dalian Construction Investment Group. Construction started in summer of 2006 with excavation of two large holes that will have the reactors put in them and a containment built around them. 'First concrete' for the first unit was poured in August 2007. 'Ground breaking' ceremony was held on 28 July 2010 for starting the work of two 1000 MWe CPR-1000 pressurized water reactors of phase II. On 17 February 2013 Hongyanhe 1 was connected to the grid, having started criticality testing on 16 January 2013.
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At a meeting of the Atomic Energy Commission on 15 March 1955, the decision was made to construct a small nuclear reactor at Trombay. The reactor would be used for training personnel for the operation of future reactors and for research, including experiments in nuclear physics, studying the effects of irradiation and the production of isotopes for medical, agricultural and industrial research. In October 1955, an agreement was signed by the United Kingdom Atomic Energy Authority and the Indian Department of Atomic Energy, under which Britain would supply uranium fuel elements for a swimming pool reactor to be designed by India. The agreement further ensured the "close cooperation and mutual assistance between the Department and the Authority in the promotion and development of the peaceful uses of atomic energy," and provided for future design and collaboration in the construction of a high flux reactor at a later date. Named Apsara, the reactor was housed in a 100 x 50 x 70 concrete building. India's and Asia's first nuclear reactor, Apsara reached criticality at 3:45 p.
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If sufficient reactivity control authority is available, the reactor can be restarted, but a xenon burn-out transient must be carefully managed. As the control rods are extracted and criticality is reached, neutron flux increases many orders of magnitude and the 135Xe begins to absorb neutrons and be transmuted to 136Xe. The reactor burns off the nuclear poison. As this happens, the reactivity increases and the control rods must be gradually re-inserted or reactor power will increase. The time constant for this burn-off transient depends on the reactor design, power level history of the reactor for the past several days (therefore the 135Xe and 135I concentrations present), and the new power setting. For a typical step up from 50% power to 100% power, 135Xe concentration falls for about 3 hours. The first time 135Xe poisoning of a nuclear reactor occurred on September 28th, 1944 in Pile 100-B at the Hanford Site. Reactor B was a Plutonium production reactor built by DuPont as part of the Manhattan Project.
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The design of a nuclear weapon is more complicated than it might seem. Such a weapon must hold one or more subcritical fissile masses stable for deployment, then induce criticality (create a critical mass) for detonation. It also is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. The procurement of a nuclear fuel is also more difficult than it might seem, since sufficiently unstable substances for this process do not currently occur naturally on Earth in suitable amounts. One isotope of uranium, namely uranium-235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium-238. The latter accounts for more than 99% of the weight of natural uranium. Therefore, some method of isotope separation based on the weight of three neutrons must be performed to enrich (isolate) uranium-235. Alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable.
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The following year the U.S. Government received the Frisch–Peierls memorandum from the UK, which stated that the amount of uranium needed for a chain reaction was far lower than had previously been thought. The memorandum was a product of the MAUD Committee, which was working on the UK atomic bomb project, known as Tube Alloys, later to be subsumed within the Manhattan Project. Eventually, the first artificial nuclear reactor, Chicago Pile-1, was constructed at the University of Chicago, by a team led by Italian physicist Enrico Fermi, in late 1942. By this time, the program had been pressured for a year by U.S. entry into the war. The Chicago Pile achieved criticality on 2 December 1942The First Reactor, U.S. Atomic Energy Commission, Division of Technical Information at 3:25 PM. The reactor support structure was made of wood, which supported a pile (hence the name) of graphite blocks, embedded in which was natural uranium oxide 'pseudospheres' or 'briquettes'. Soon after the Chicago Pile, the U.S. military developed a number of nuclear reactors for the Manhattan Project starting in 1943.
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In May, 1967, the Atomic Energy Commission (AEC), predecessor to the Nuclear Regulatory Commission (NRC), issued the official construction permit (number 32) for Point Beach Unit 1. The Unit 2 construction permit (number 47) was issued approximately a year later. On October 5, 1970, the AEC issued its full-term, full-power Operating License (DPR-24) for Point Beach Unit 1. The loading fuel into the reactor commenced almost immediately. On November 2, 1970, operators achieved initial criticality, with the nuclear-powered electricity being produced four days later, on November 6. Full commercial service was reached on December 21, 1970, just 49 months from the initial groundbreaking ceremony. After delays from nuclear power opponents, Unit 2 was granted a full-term, full-power operating license (DPR-27) on March 8, 1973, almost 1 1/2 years behind the original schedule. Due to steam generator tube degradation and failures caused by intergranular stress corrosion cracking, Unit 1 was operated at approximately 75-80% of full power from December 1979 until October 1983, when replacement steam generators were installed.
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Operation Crossroads Test Able, a 23-kiloton air-deployed nuclear weapon detonated on July 1, 1946. This bomb used, and consumed, the infamous Demon core that took the lives of two scientists in two separate criticality accidents. nuclear tests at the Nevada Test Site. Between 1940 and 1996, the U.S. spent at least $ in present-day terms on nuclear weapons development, including platforms development (aircraft, rockets and facilities), command and control, maintenance, waste management and administrative costs. It is estimated that, since 1945, the United States produced more than 70,000 nuclear warheads, which is more than all other nuclear weapon states combined. The Soviet Union/Russia has built approximately 55,000 nuclear warheads since 1949, France built 1110 warheads since 1960, the United Kingdom built 835 warheads since 1952, China built about 600 warheads since 1964, and other nuclear powers built less than 500 warheads all together since they developed their first nuclear weapons. Until November 1962, the vast majority of U.S. nuclear tests were aboveground. After the acceptance of the Partial Test Ban Treaty, all testing was regulated underground, in order to prevent the dispersion of nuclear fallout.
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Although protactinium is located in the periodic table between uranium and thorium, which both have numerous applications, there are currently no uses for protactinium outside scientific research owing to its scarcity, high radioactivity, and high toxicity. Protactinium-231 arises from the decay of uranium-235 formed in nuclear reactors, and by the reaction 232Th + n → 231Th + 2n and subsequent beta decay. It was once thought to be able to support a nuclear chain reaction, which could in principle be used to build nuclear weapons: the physicist once estimated the associated critical mass as .Seifritz, Walter (1984) Nukleare Sprengkörper – Bedrohung oder Energieversorgung für die Menschheit, Thiemig-Verlag, . However, the possibility of criticality of 231Pa has been ruled out since then. With the advent of highly sensitive mass spectrometers, an application of 231Pa as a tracer in geology and paleoceanography has become possible. So, the ratio of protactinium-231 to thorium-230 is used for radiometric dating of sediments which are up to 175,000 years old and in modeling of the formation of minerals. In particular, its evaluation in oceanic sediments allowed to reconstruct the movements of North Atlantic water bodies during the last melting of Ice Age glaciers.
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Nuclear weapons use fission as either the partial or the main energy source. Depending on the weapon design and where it is exploded, the relative importance of the fission product radioactivity will vary compared to the activation product radioactivity in the total fallout radioactivity. The immediate fission products from nuclear weapon fission are essentially the same as those from any other fission source, depending slightly on the particular nuclide that is fissioning. However, the very short time scale for the reaction makes a difference in the particular mix of isotopes produced from an atomic bomb. For example, the 134Cs/137Cs ratio provides an easy method of distinguishing between fallout from a bomb and the fission products from a power reactor. Almost no caesium-134 is formed by nuclear fission (because xenon-134 is stable). The 134Cs is formed by the neutron activation of the stable 133Cs which is formed by the decay of isotopes in the isobar (A = 133). So in a momentary criticality, by the time that the neutron flux becomes zero too little time will have passed for any 133Cs to be present.
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Since 2014, Hedva has served as the Director of Advocacy for the Processing Foundation, an auxiliary operation to the Processing open source computer programming project with the goal "to empower people of all interests and backgrounds to learn how to program and make creative work with code, especially those who might not otherwise have access to these tools and resources." Hedva joined the project based on their political activism, and their commitment to "open-source philosophy and practice, decolonial politics and action, and to promoting the attenuation of the boundaries between creative disciplines of all kinds" During a talk at a Processing conference on diversity, Hedva spoke about their goals for the Processing Foundation as "an institution defined by having to constantly re-institute itself," characterized by continuous growth and criticality. In their role with the foundation, Hedva helped establish a fellowship program in 2015, which focuses on issues of access to Processing software across society. Speaking on the program, Hedva states that "technology can be both a viable artistic medium as well as a model for sociality," where tools are learned and developed through exploration and collaboration.
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