Abstract

Inservice inspection (ISI) of passive nuclear components can effectively ensure that aging-related degradation is managed and mitigated throughout the life of a nuclear reactor. However, the basis for the Code-required inspection interval, e.g., typically 10-years, is not clearly documented. Additionally, inspection programs for new and advanced reactors may not be compatible with the inspection methodology used by the current fleet light water reactors, and therefore other methods may be needed. Over the last several years, the U.S. Nuclear Regulatory Commission has approved plant-specific extensions to in-service inspection intervals with a basis that includes operational experience and risk-informed arguments. In some cases, requests have been made to extend this interval to the end of licensed life of the plant, resulting in possible inspection elimination. This paper describes some considerations for the performance monitoring needed to ensure that the analyses supporting inspection interval extensions remain valid throughout the operating life of the associated components. Further, special challenges associated with the development of performance monitoring strategies are discussed. While there may be many options in developing a robust performance monitoring program, this paper presents some initial thoughts on how statistical methods may be used to develop some aspects of a performance monitoring program that can be used in conjunction with detailed analyses to justify the extension of inservice inspection intervals, while continuing to ensure plant safety.

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