Effect analysis of the intentional depressurization on fission product behavior during TMLB' severe accident

Effect analysis of the intentional depressurization on fission product behavior during TMLB' severe accident 1 corresp first-author Corresponding author. E-mail address: huanggaofeng@sjtu.edu.cn Corresponding author. E-mail address: huanggaofeng@sjtu.edu.cn huanggaofeng@sjtu.edu.cn 1 1 1 School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China It has been found that the pressure in the reactor coolant system (RCS) remains high in some severe accident sequences at the time of reactor vessel failure, with the risk of causing direct containment heating (DCH). Intentional depressurization is an effective accident management strategy to prevent DCH or to mitigate its consequences. Fission product behavior is affected by intentional depressurization, especially for inert gas and volatile fission product. Because the pressurizer power-operated relief valves (PORVs) are latched open, fission product will transport into the containment directly. This may cause larger radiological consequences in containment before reactor vessel failure. Four cases are selected, including the TMLB' base case and the opening one, two and three pressurizer PORVs. The results show that inert gas transports into containment more quickly when opening one and two PORVs, but more slowly when opening three PORVs; more volatile fission product deposit in containment and less in reactor coolant system (RCS) for intentional depressurization cases. When opening one PORV, the phenomenon of revaporization is strong in the RCS. Fission product behavior Depressurization TMLB' accident Severe accident References Sandia National Laboratory . Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants. USNRC NUREG-1150 , 1990 . Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants. USNRC NUREG-1150 Brownson D A , Haney L N , Chien N D . Intentional Depressurization Accident Management Strategy for PWR. USNRC NUREG/CR-5937 , 1993 . Intentional Depressurization Accident Management Strategy for PWR. USNRC NUREG/CR-5937 Southern California Edison . Individual Plant Examination Report for San Onofre Nuclear Generating Station Units 2 and 3 , 1993 . Individual Plant Examination Report for San Onofre Nuclear Generating Station Units 2 and 3 NEA . Insights into the control of the release of iodine, cesium, strontium and other fission product in the containment by severe accident management. OECD NEA/CSNI/Rv(2000)9 , 2000 . Insights into the control of the release of iodine, cesium, strontium and other fission product in the containment by severe accident management. OECD NEA/CSNI/Rv(2000)9 Herranz L E , Ball J , Auvinen A , et al . Progress in Understanding Key Aerosol Issues . The 3rd European Review Meeting on Severe Accident Research , Nesseber, Bulgaria , 2008 . Progress in Understanding Key Aerosol Issues Auvinen A , Lehtinen K E J , Enriquez J , et al . J Aerosol Sci , 2000 , 31 : 1029 - 1043 . J Aerosol Sci Jokiniemi J , Auvinen A . A model for Fission Product Revaporisation in Severe Nuclear Power Plant Accidents . VTT Processes. Espoo, Finland, Project Report PRO3/P31/03 , 2003 . A model for Fission Product Revaporisation in Severe Nuclear Power Plant Accidents NEA . State of the art report of iodine chemistry. OECD NEA/CSNI/R (2007)1 , 2007 . State of the art report of iodine chemistry. OECD NEA/CSNI/R (2007)1 10.13538/j.1001-8042/nst.20.373-379 Supported by National Basic Research Program of China (No.2009CB724301) 2009-04-27 2009-12-20 2021-01-19 2009 Nuclear Science and Techniques 06 20