SENSITIVITY ANALYSIS ON THE DETAILED PLANT OPERATIONAL STATE FOR SHUTDOWN PSA

摘要

Probabilistic Safety Assessment (PSA) for the plant shutdown state of nuclear power plants is performed based on Plant Operational States (POSs) which depend on periodic inspections and maintenance. For a typical BWR, the shutdown POSs are defined in consideration of various plant conditions: boundaries of Primary Containment Vessel (PCV)/ Reactor Pressure Vessel (RPV), reactor water level, availability of mitigation systems and temperature/pressure of primary coolant. The shutdown POSs for a BWR plant may involve conservative simplifications. One of the simplifications is treatment of PCV/RPV heads conditions during the POSs involving their opening/closing operations. Usually the PCV/RPV heads conditions are assumed to be the most onerous in terms of accident sequence modelling on both Level 1 and 2 PSA. In this study, a sensitivity analysis is performed to understand the significance of the conservatism by refining the POSs which involve opening/closing operations of PCV/RPV heads.