Evaluations of core melt frequency effects due to component aging and maintenance

A methodology is developed to incorporate aging effects into a Probabilistic Risk Analysis (PRA). The methodology separates the PRA models from the aging models, allowing available PRAs to be efficiently used in evaluating risk effects of aging. The methodology is applied to two PRAs to demonstrate the results which are obtainable from current PRAs. Various component aging rates and various surveillance and maintenance programs are evaluated to determine their impacts on the resulting core melt frequency. Both point evaluations and uncertainty evaluations are carried out. The results of the applications show that for given aging rates, the core melt frequency impacts are very sensitive to the surveillance and maintenance program which is carried out. The detailed results which are obtained allow the aging contributors to be effectively prioritized to focus aging management programs.