Fatigue life evaluation for reactor pressure vessels

In terms of plant safety, the reactor pressure vessel is one of the most critical pressure boundary components in the nuclear power plant. The primary degradation mechanisms for reactor pressure vessels are irradiation embrittlement and thermal fatigue. The effects of irradiation and fatigue damage should then be considered in determining the overall lifetime of the reactor pressure vessel. For the radiation damage, related issues have been studied. For the case of fatigue resulting from the pressure and temperature changes, however, relatively less attention has been paid. The fatigue damage is generally regarded as one of the limiting factors for the safe operation life of the reactor pressure vessel. In this paper, the simplified fatigue damage evaluation procedures are applied to the commercially operating reactor vessel which is currently subjected to plant lifetime management study. Specifically, fatigue lifetime evaluation procedures for RPV inlet/outlet nozzles, shell and studs are therefore investigated based on the design basis approaches and the evaluation results are presented based on the assumed operating transient occurrences