A drywell containment building which resembles an inverted lightbulb above the wetwell which is a steel torus containing water.
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In its lowest, partially underground part is located the 1.7–1.8 m thick steel and concrete pressure suppression drywell. The structure is able to withstand an earthquake. In case of a plane crash, however, the building could be damaged. The reactor would nevertheless remain intact due to the five 30–50 cm thick insoles and the massive drywell.. In German.
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Described as an "over-under" configuration with the drywell forming a truncated cone on a concrete slab. Below is a cylindrical suppression chamber made of concrete rather than just sheet metal.
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The MUWC and the makeup water purification and filtering (MUPF) systems were also used to try to cool the suppression pool and drywell in addition to the reactor to prevent the drywell pressure from getting too high. Operators were later able to restore the High Pressure Core Spray portion of the ECCS in unit 4 and switched emergency water injection for unit 4 from the MUWC system to the HPCS. While the water level was maintained in the three cores using emergency water injection, pressures in the containment vessel continued to rise due to lack of suppression pool cooling and the operators prepared to vent the containments making restoration of heat removal urgent. Unit 1 was prioritized as it had the highest drywell pressure.
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Like other BWRs, the actual containment vessel for the reactor is a separate drywell/torus structure enclosed within the reactor building, but structurally separate. The outer reactor building serves as secondary containment and houses many of the reactor's safety systems.
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Sometimes a drywell with a series of gravel layers near the lowest spot in the rain garden will help facilitate percolation and avoid clogging at the sedimentation basin. However, a drywell placed at the lowest spot can become clogged with silt prematurely, turning the garden into an infiltration basin and defeating its purpose as a bioretention system. The more polluted the runoff water, the longer it must be retained in the soil for purification. Capacity for a longer purification period is often achieved by installing several smaller rain garden basins with soil deeper than the seasonal high water table.
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Old drywell A dry well or drywell is an underground structure that disposes of unwanted water, most commonly surface runoff and stormwater and in some cases greywater. It is a covered, porous-walled chamber that allows water to slowly soak into the ground (that is, percolate), dissipating into the groundwater. Such structures are often called a soakaway in the United Kingdom, a soakwell in Australia, and a soak pit in India. A sump in a basement can be built in dry well form, allowing the sump pump to cycle less frequently (handling only occasional peak demand).
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The description of this accident is applicable for the BWR/4. The immediate result of such a break (call it time T+0) would be a pressurized stream of water well above the boiling point shooting out of the broken pipe into the drywell, which is at atmospheric pressure. As this water stream flashes into steam, due to the decrease in pressure and that it is above the water boiling point at normal atmospheric pressure, the pressure sensors within the drywell will report a pressure increase anomaly within it to the reactor protection system at latest T+0.3. The RPS will interpret this pressure increase signal, correctly, as the sign of a break in a pipe within the drywell. As a result, the RPS immediately initiates a full SCRAM, closes the main steam isolation valve (isolating the containment building), trips the turbines, attempts to begin the spinup of RCIC and HPCI, using residual steam, and starts the diesel pumps for LPCI and CS. Now let us assume that the power outage hits at T+0.5.
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Small leaks may be compensated by the redundant alternate low pressure system (ALPS). By loss of cooling agent in the drywell, the excessive water will spread into a torus-shaped pressure- suppression pool. The 4000 m3 big torus is filled with 2000 m3 water. and is in turn cooled by a redundant torus cooling system and a redundant shutdown and torus cooling system with a total of 4·100% residual heat removal capacity.
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In 1989, the Masonic Temple was listed in A Guide to Florida's Historic Architecture, published by the University of Florida Press. On October 20, 2000, the City of Inverness placed a commemorative plaque on the building. The building was purchased by the Drywell Group, LLC in 2006 and they proceeded to renovate and restore the interior and exterior. Wood floors and windows were refinished, period furniture, lighting, art, and paint colors were added throughout the building.
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The walls were relatively intact compared to later explosions at Units 3 and 4. Video of the explosion shows that it was primarily directed sideways.Fukushima (Japan) Nuclear Power Plant Explosion 12 March 2011 - YouTube The roof of the building was designed to provide ordinary weather protection for the areas inside, not to withstand the high pressure of an explosion. In the Fukushima I reactors the primary containment consists of "drywell" and "wetwell" concrete structures below the top level, immediately surrounding the reactor pressure vessel.
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At that meeting, several of the local residents were opposed to re-licensing of the nuclear power plant.Examiner, June 28, 2007, Oyster Creek's time is up, residents tell board The ASLB's decision on May 31, 2007 hearing led to a full public hearing on the issue of the monitoring of corrosion in the plant's drywell liner. The hearing was scheduled for September 24, 2007 in the county seat Toms River.Asbury Park Press, June 20, 2007, In 2008, the Atomic Safety and Licensing Board twice rejected citizens' contentions concerning Oyster Creek.
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In earlier versions of the BWR (BWR 1 or 2 plants), the LPCS system was the only ECCS, and the core could be adequately cooled by core spray even if it was completely uncovered. Starting with Dresden units 2 and 3, the core spray system was augmented by the HPCI/LPCI systems to provide for both spray cooling and core flooding as methods for ensuring adequate core cooling. Versioning note: In ABWRs and (E)SBWRs, there are additional water spray systems to cool the drywell and the suppression pool.
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Pumps were designed to circulate hot fluid from the reactor to be cooled in the wetwell, but only units 5 and 6 had any power. Units 1, 2 and 3 reactor cores overheated and melted. Radioactivity was released into the air as fuel rods were damaged due to overheating by exposure to air as water levels fell below safe levels. As an emergency measure, operators resorted to using firetrucks and salvaged car batteries to inject seawater into the drywell to cool the reactors, but only achieved intermittent success and three cores overheated.
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On 11 October 2012, TEPCO released results of the first direct inspections (by remotely operated camera) of conditions in the interior of the Reactor 1 PCV.Ashai Shimbun (11/10/2012) These suggest that the initial assumptions concerning the behaviour of the fuel mass during the accident may have been incorrect. In particular, the distribution of radiation levels within the PCV, with peak levels being around the bottom head of the RPV, suggest that the majority of the fuel has in fact been retained within the RPV. Radiation levels are also notably lower around the lower parts of the "Drywell", suggesting that fuel had not reached the bottom of the containment vessel, or damaged the concrete floor slab.
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The core is cooled rapidly and completely, and following cooling to a reasonable temperature, below that consistent with the generation of steam, CS is shut down and LPCI is decreased in volume to a level consistent with maintenance of a steady-state temperature among the fuel rods, which will drop over a period of days due to the decrease in fission-product decay heat within the core. After a few days of LPCI, decay heat will have sufficiently abated to the point that defueling of the reactor is able to commence with a degree of caution. Following defueling, LPCI can be shut down. A long period of physical repairs will be necessary to repair the broken recirculation loop; overhaul the ECCS; diesel pumps; and diesel generators; drain the drywell; fully inspect all reactor systems, bring non-conformal systems up to spec, replace old and worn parts, etc.
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"Although we cannot directly check it, it's highly likely happening". In April 2011 the United States Nuclear Regulatory Commission said that some of the core of a stricken Japanese reactor had probably leaked from its steel pressure vessel into the bottom of the containment structure, implying that the reactor damage was worse than previously thought. If molten fuel has "left the reactor’s pressure vessel and reached the drywell in substantial quantities, it raises the possibility that the fuel could escape the larger containment structure, leading to a large-scale radioactive release". According to the Federation of Electric Power Companies of Japan, "by April 27 approximately 55 percent of the fuel in reactor unit 1 had melted, along with 35 percent of the fuel in unit 2, and 30 percent of the fuel in unit 3; and overheated spent fuels in the storage pools of units 3 and 4 probably were also damaged".
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