Comparison of two approaches for establishing performance criteria related to Maintenance Rule

Abstract

Probabilistic safety assessment (PSA) serves as a tool for systemically analyzing the safety of nuclear power plants. This paper explains and compares two approaches for the establishment of performance criteria related to the Maintenance Rule: (1) the individual reliability-based approach, and (2) the PSA importance measure-based approach. Different characteristics of the two approaches were compared in a qualitative manner, while a quantitative comparison was performed through application of the two approaches to a nuclear power plant. It was observed that the individual reliability-based approach resulted in more conservative performance criteria, compared to the PSA importance measure-based approach. It is thus expected that the PSA importance measure-based approach will allow for more flexible maintenance policy under conditions of limited resources, while providing for a macroscopic view of overall plant safety. Based on insights derived through this analysis, we emphasize the importance of a balance between reliability and safety significance, and propose a balance measure accordingly. The conclusions of this analysis are likely to be applicable to other types of nuclear power plants.