Common cause failure analysis and reliability parameter estimation of mechanical components for the nuclear power plants in Japan

A general conclusion from probabilistic safety assessments (PSAs) of commercial nuclear power plants is that common cause failures (CCFs) are significant contributor to the unavailability of safety systems and the risk of nuclear plant accidents. Although it is desirable for the domestic operating experience to be reflected in the reliability parameters to improve the quality of PSA, the CCF reliability parameters used in Japan still rely on obsolete U.S. generic data developed in 1980s. In this study, CCF event analysis of mechanical components in the commercial nuclear power plants in Japan were performed using the data recorded in NUCIA from 1982 to 2007. In addition, CCF reliability parameters were estimated for the PSA in Japan. (author)