Risk-informed developments and comparisons for the safety related valves of Inservice Testing Program at Taiwan BWR and PWR nuclear power plants

Abstract

Safety related valves within the nuclear power plant were governed by the Inservice Testing Program (IST) for scheduling tests or maintenances during the plant normal operation. Based on the program definitions, series of tests for these valves have to be performed and conducted periodically. Safety functions of safety related valves such as Motor Operated Valve (MOV), Air Operated Valve (AOV) and Check Valve (CV) under the event of Design Basis Accident (DBA) could be performed properly. IST program plays an important role for constantly maintaining these safety related valves under operable conditions; therefore safety functions such as emergency reactivity control, post-accident residue heat removal, post-accident radioactivity removal and containment isolation could be performed and satisfied during the DBA event or abnormal plant operation occurrences.This study performed the Risk-informed evaluations for safety related valves in the IST program for BWR and PWR nuclear power plants in Taiwan. Outcome from this study, safety classifications for the safety related valves under IST program could be categorized, HSSC category valves could be identified, testing frequency relieves for the LSSC category could be suggested, systematic comparison of the safety significant classification between BWR and PWR nuclear power plants was presented and finally, due to the advantages of the RI-IST, both dose exposure for the plant staffs and outage cost reductions for the utility managements could be achieved.