A number of PSA (Probabilistic Safety Assessment) studies have been applied to the optimization of maintenance activities in nuclear power plans from a viewpoint of safety focusing on the risks of core meltdown. However, even a small-scale incident of component, which never causes the core meltdown, resulted in the reactor shutdown and economic losses. The economic losses due to this kind of incident become enormous when including the losses that are not officially counted. Accordingly, in addition to the safety analysis focusing on the risk of core meltdown, it is very useful to establish a model that can plan maintenance strategies in terms of availability and economic efficiency of nuclear power plants.

With the background above mentioned, we have been developing an integrated simulator for the maintenance optimization of LWRs (Light Water Reactors) based on PFM (Probabilistic Fracture Mechanics). The concept of the simulator is to provide a method to optimize maintenance activities for representative components and piping systems in nuclear power plants totally and quantitatively in terms of safety, availability and economic efficiency (both from cost and profit). The simulator will also provide a guideline regarding social acceptance of the risk-based decision makings. This study has been conducted under “Innovative and Viable Nuclear Energy Technology (IVNET) Development Project” financially supported by Japanese METI (Ministry of Economy, Trade and Industry).