Optimization of the Surveillance Test Interval of Integrated Leakage Rate Test at a PWR Plant in Taiwan

摘要

After the USNRC issued the option B of 10CFR50, appendix J in September 1994, many utilities had chosen the risk-informed performance-based (RIPB) option B as their integrated leakage rate test (ILRT) guideline. In this study, the optimization of the surveillance test interval (STI) of ILRT at a PWR plant in Taiwan was surveyed. Over 180 kinds of containment isolation valves (CIVs) of the plant and the risk impacts of these valves to the internal PRA models for power operation and shutdown conditions were examined. All of the risk incremental and diminishing factors were discussed. It was found that only the diminishing risk factor caused by the less failure of CIVs, which were detected by the STI extension of ILRT, was required to be included in the modified PRA models. For the internal, power operation PRA model resulted from the STI extension of ILRT, the changes of core damage frequency (CDF) at 1.2E-9/ry and large early release frequency (LERF) at 4.2E-7/ry were evaluated. According to the acceptance criteria of RG 1.174, the option B of 10CFR50, appendix J was also suggested to be applied to optimize the STI of ILRT of the PWR plant.