A Study on State-of-the-Art Technology for Common Cause Failures Analysis and Suggestions

Common Cause Failures (CCFs) means the event that more than a component fails simultaneously or in similar time due to a shared cause. Two ground rules to guarantee the safety of Nuclear Power Plants are redundancy and diversity. However, the result of Probabilistic Safety Assessment (PSA) shows that CCFs contributes to the Core Damage Frequency (CDF) and system unavailability because CCFs damages the redundancy, which can defeat the redundancy employed to improve the reliability of safety functions in NPPs. Therefore, it is necessary to correctly analyze the CCFs with an appropriate procedure because CCFs is very sensitive issue in PSA results. Therefore, it is important to estimate how CCFs affects risk. According to this, the studies on the methodology of CCFs analysis have been issued, and Risk-Informed Application (RIA) makes the studies on CCFs uncertainty more active. In this paper, state-of-the-art technology of CCFs analysis and suggestions to resolve technical problems related to CCFs for the future are provided