The effect of an aggressive cool-dowm following a refueling outage accident in which a pressurizer safety valve is stuck open

A PSV(Pressurizer Safety Valve) popping test carried out in the early phases of a refueling outage may trigger a test-induced LOCA(Loss Of Coolant Accident) if a PSV fails to fully close and is stuck in a partially open position. According to a KSNP(Korea Standard Nuclear Power Plant) low power and shutdown PSA(Probabilistic Safety Assessment), the failure of a High Pressure Safety Injection (HPSI) accompanied by the failure of a PSV to fully close was identified as a dominant accident sequence with a significant impact on Low Power and Shutdown Risks (LPSR). In this study, we aim to investigate and verity a new means for mitigating this type of accident using a thermal-hydraulic analysis. In particular, we explore the applicability of an aggressive cool-down combined with operator actions. The results of the various sensitivity studies performed here will help reduce LPSR and improve refueling outage safety