To mitigate consequences of core melting,an ex-vessel core catcher is investigated in this study.Instructions should be obeyed to cool down the corium caused by core melting.The corium destroys the reactor containment...To mitigate consequences of core melting,an ex-vessel core catcher is investigated in this study.Instructions should be obeyed to cool down the corium caused by core melting.The corium destroys the reactor containment and causes radioactive materials to be released into the environment if it does not cool down well.It is important to build a core catcher system for the reception,localization,and cool down of the molten corium during a severe accident resulting from core melting.In this study,the role of a core catcher in the VVER-1000/v528 reactor containment during a station black out(SBO)accident is evaluated using the MELCOR1.8.6 code.In addition,parametric analyses of the SBO for(i)SBO accidents with emergency core cooling system(ECCS)operation,and(ii)without ECCS operation are performed.Furthermore,thermal–hydraulic analyses in dry and wet cavities with/without water are conducted.The investigations include the reduction of gases resulting from molten–corium–concrete interactions(H_(2),CO,CO_(2)).Core melting,gas production,and the pressure/temperature in the reactor containment are assessed.Additionally,a full investigation pertaining to gas release(H_(2),CO,CO_(2))and the pressure/temperature of the core catcher is performed.Based on MELCOR simulations,a core cavity and a perimeter water channel are the best options for corium cooling and a lower radionuclide release.This simulation is also theoretically investigated and discussed herein.The simulation results show that the core catcher system in addition to an internal sacrificial material reduces the containment pressure from 689 to 580 kPa and the corresponding temperature from 394 to 380 K.Furthermore,it is observed that the amount of gases produced,particularly hydrogen,decreased from 1698 to 1235 kg.Moreover,the presence of supporting systems,including an ECCS with a core catcher,prolonged the core melting time from 16,430 to 28,630 s(in an SBO accident)and significantly decreased the gases produced.展开更多
OECD/NEA （Organization for Economic Cooperation and Development/Nuclear Energy Agency） launched the SERENA （steam explosion resolution for nuclear application） project to resolve internationally the ex-vessel stea...OECD/NEA （Organization for Economic Cooperation and Development/Nuclear Energy Agency） launched the SERENA （steam explosion resolution for nuclear application） project to resolve internationally the ex-vessel steam explosion issue, which is one of major unresolved issues after a TMI-2 （three mile island-2） accident. One of main conclusions of OECD/NEA SERENA Phase 1, which was completed in 2005, was that some damage to the cavity is to be expected for an ex-vessel explosion. One major uncertainty that does not allow for a convergence toward consistent predictions was that there are no data on the component distribution in a pre-mixture at the time of an explosion, especially the level of the void. The other major uncertainty is the explosion behavior of corium melts. Therefore, SERENA Phase 2 was launched on October 1, 2007 to resolve the uncertainties of the coolant void and material effect by performing a limited number of well-designed tests with advanced instrumentation reflecting a large spectrum of ex-vessel melt compositions and conditions, and the required analytical work to bring the code capabilities to a sufficient level for use in reactor case analyses. The recent status of the OECD-SERENA Phase 2 project for the resolution of ex-vessel steam explosion risks will be described.展开更多
The LIVE （Late In-Vessel Phase Experiments） test program investigates in-vessel melt pool behaviour and cooling strategies for in-vessel corium retention during severe accidents in light water reactors （LWR）. The ...The LIVE （Late In-Vessel Phase Experiments） test program investigates in-vessel melt pool behaviour and cooling strategies for in-vessel corium retention during severe accidents in light water reactors （LWR）. The main part of the LIVE facility is a 1：5 scaled semi-spherical lower head of a typical pressurized water reactor. Up to now, LIVE experiments have been performed in different initial external cooling conditions, melt volumes and internal heat generations. At present the well-known simulant material KNO3-NaNO3 in non-eutectic composition （80 mole% KNO3-20 mole% NaNO3） and in eutectic composition （50 mole% KNO3- 50 mole% NaNO3） is used in the live program. The 3D heat flux distribution through vessel wall, melt pool temperature, crust thickness and the pool melt composition can be measured or determined. Extensive results have been obtained concerning the melt pool thermal hydraulic behaviour in transient and in steady state conditions.展开更多
To prevent direct contact of the melt and basemat concrete of the cavity in a postulated core melt accident, a core catcher concept is suggested. Upon ablation of the sacrificial layer on top of the core catcher while...To prevent direct contact of the melt and basemat concrete of the cavity in a postulated core melt accident, a core catcher concept is suggested. Upon ablation of the sacrificial layer on top of the core catcher while molten core material is discharged, a mixture of water and gas is injected from below. It is expected that a simultaneous injection of water and gas could prevent a possible steam explosion/spike and also suppress the rapid release of steam which might result in fast over-pressurization of the containment. A test facility for the core catcher using a thermite reaction technique for the generation of the melt was designed and constructed at Korea Atomic Energy Research Institute （KAERI）. The first series of tests were performed by using a mixture of Al, Fe2O3, and CaO as a stimulant. As a first try, only water was injected from the bottom of the melt through five water injection nozzles when the melt front reached the water injection nozzles. A description of the test facility for the core catcher, the thermite composition, and the methods of experiment is included. The test results are discussed.展开更多
文摘To mitigate consequences of core melting,an ex-vessel core catcher is investigated in this study.Instructions should be obeyed to cool down the corium caused by core melting.The corium destroys the reactor containment and causes radioactive materials to be released into the environment if it does not cool down well.It is important to build a core catcher system for the reception,localization,and cool down of the molten corium during a severe accident resulting from core melting.In this study,the role of a core catcher in the VVER-1000/v528 reactor containment during a station black out(SBO)accident is evaluated using the MELCOR1.8.6 code.In addition,parametric analyses of the SBO for(i)SBO accidents with emergency core cooling system(ECCS)operation,and(ii)without ECCS operation are performed.Furthermore,thermal–hydraulic analyses in dry and wet cavities with/without water are conducted.The investigations include the reduction of gases resulting from molten–corium–concrete interactions(H_(2),CO,CO_(2)).Core melting,gas production,and the pressure/temperature in the reactor containment are assessed.Additionally,a full investigation pertaining to gas release(H_(2),CO,CO_(2))and the pressure/temperature of the core catcher is performed.Based on MELCOR simulations,a core cavity and a perimeter water channel are the best options for corium cooling and a lower radionuclide release.This simulation is also theoretically investigated and discussed herein.The simulation results show that the core catcher system in addition to an internal sacrificial material reduces the containment pressure from 689 to 580 kPa and the corresponding temperature from 394 to 380 K.Furthermore,it is observed that the amount of gases produced,particularly hydrogen,decreased from 1698 to 1235 kg.Moreover,the presence of supporting systems,including an ECCS with a core catcher,prolonged the core melting time from 16,430 to 28,630 s(in an SBO accident)and significantly decreased the gases produced.
文摘OECD/NEA （Organization for Economic Cooperation and Development/Nuclear Energy Agency） launched the SERENA （steam explosion resolution for nuclear application） project to resolve internationally the ex-vessel steam explosion issue, which is one of major unresolved issues after a TMI-2 （three mile island-2） accident. One of main conclusions of OECD/NEA SERENA Phase 1, which was completed in 2005, was that some damage to the cavity is to be expected for an ex-vessel explosion. One major uncertainty that does not allow for a convergence toward consistent predictions was that there are no data on the component distribution in a pre-mixture at the time of an explosion, especially the level of the void. The other major uncertainty is the explosion behavior of corium melts. Therefore, SERENA Phase 2 was launched on October 1, 2007 to resolve the uncertainties of the coolant void and material effect by performing a limited number of well-designed tests with advanced instrumentation reflecting a large spectrum of ex-vessel melt compositions and conditions, and the required analytical work to bring the code capabilities to a sufficient level for use in reactor case analyses. The recent status of the OECD-SERENA Phase 2 project for the resolution of ex-vessel steam explosion risks will be described.
文摘The LIVE （Late In-Vessel Phase Experiments） test program investigates in-vessel melt pool behaviour and cooling strategies for in-vessel corium retention during severe accidents in light water reactors （LWR）. The main part of the LIVE facility is a 1：5 scaled semi-spherical lower head of a typical pressurized water reactor. Up to now, LIVE experiments have been performed in different initial external cooling conditions, melt volumes and internal heat generations. At present the well-known simulant material KNO3-NaNO3 in non-eutectic composition （80 mole% KNO3-20 mole% NaNO3） and in eutectic composition （50 mole% KNO3- 50 mole% NaNO3） is used in the live program. The 3D heat flux distribution through vessel wall, melt pool temperature, crust thickness and the pool melt composition can be measured or determined. Extensive results have been obtained concerning the melt pool thermal hydraulic behaviour in transient and in steady state conditions.
文摘To prevent direct contact of the melt and basemat concrete of the cavity in a postulated core melt accident, a core catcher concept is suggested. Upon ablation of the sacrificial layer on top of the core catcher while molten core material is discharged, a mixture of water and gas is injected from below. It is expected that a simultaneous injection of water and gas could prevent a possible steam explosion/spike and also suppress the rapid release of steam which might result in fast over-pressurization of the containment. A test facility for the core catcher using a thermite reaction technique for the generation of the melt was designed and constructed at Korea Atomic Energy Research Institute （KAERI）. The first series of tests were performed by using a mixture of Al, Fe2O3, and CaO as a stimulant. As a first try, only water was injected from the bottom of the melt through five water injection nozzles when the melt front reached the water injection nozzles. A description of the test facility for the core catcher, the thermite composition, and the methods of experiment is included. The test results are discussed.
