Accident progression analyses of a BWR with filtered containment venting system during long term severe accident conditions

It is expected that filtered containment venting system (FCVS) would play an important role to reduce the amount of fission products (FPs) released to the environment during severe accident conditions. Experimental studies for FCVS have been conducted in CRIEPI, and decontamination factors (DFs) regarding internal impaction at nozzles, Venturi’s scrubbers, metal fibrous filters, and Zeolite filters have been measured and formulated, respectively. The DF models were implemented into the MELCOR input data assuming a typical advanced boiling water reactor (ABWR). Several accident progression analyses, such as large break loss-of-coolant accident (LOCA), long term station blackout (LTSBO), and loss-of-all power supply, were conducted for the BWR with a FCVS that consists of scrubbers, metal and Zeolite filters connected to its suppression pool and dry well. The result indicated that as the water level of the FCVS was decreased, efficiency of scrubber was decreased, and the total DF was governed by metal fibrous filter. After most of the water in FCVS was evaporated, FCVS temperature increased, and FPs once captured by the FCVS and deposited on wall inside of the system were transported the environment. Time-depended release ratios of Cs, CsI, Te, Sr to the environment were compared under condition with FCVS and that without FCVS. The results obtained effectiveness of FCVS for each FP. The results also gave some insights for implementation of FCVS and severe accident management for BWRs.