Maintenance risk management in Dayabay nuclear power plant

The importance of proper maintenance to safe and reliable nuclear plant operation has long been recognized by the nuclear utility and regulatory body. This paper presents a process of maintenance risk management developed for a Chinese Nuclear Power Plant (NPP). The process includes three phases: (I) long term maintenance plan risk management, (II) monthly maintenance plan risk management, and (III) detailed risk management for high risk configuration. A risk matrix is developed for phase I whose purpose is to provide a rough guide for risk management in the making of the annual maintenance plan. For Phase II and Phase III, a software tool named Maintenance- Risk-Monitor is developed based on the internal initiating event, level 1 PSA model. The results of Phase II are the risk information of the all plant configurations caused by the unavailability of the components included the monthly maintenance plan. When the increase of core damage frequency (CDF) or the incremental core damage probability (ICDP) of a configuration is higher than the corresponding thresholds, Phase III is needed for this high risk configuration to get the useful information such as risk-importance components, human actions and initial events, from which appropriate preventive measurements could be derived. It is hoped that the provided process of maintenance risk management, together with the developed software tool, could facilitate the maintenance activities in the NPPs of China. (authors)