PRA IMPORTANCE MEASURES FOR MAINTENANCE PRIORITIZATION APPLICATIONS

Various importance measures are standardly calculated in a standard probabilistic risk assessment (PRA). Approaches are developed in this paper for using two of these measures-the minimal cutset contribution and the risk reduction importance-for prioritizing the risk importances of maintenances. One approach which is developed prioritizes maintenances based on the risk importance of the associated contributor. The second approach prioritizes maintenances based on the risk impact if the maintenance is ineffective. The core damage frequency is used as the risk measure for prioritization. The demonstration studies, which are carried out using the Surry Plant PRA, indicate that the two approaches give similar results if appropriate cutoff criteria are used. As an additional evaluation, risk unimportant maintenances are identified using the risk increase importance, or risk achievement worth, calculated in the PRA.