Life Cycle Management Evaluations of Safety Related Service Water Systems at Nuclear Power Plants

Abstract

All US nuclear power plants have been inspecting buried safety related piping as part of their required NEI 09-14 response, maintaining their ongoing and enduring commitment to ensuring buried pipe integrity. Prior service water systems experience and those buried piping inspections have revealed a small number of pinholes, both in Above Ground Piping (AGP) and some excavated buried service water piping. The majority of those leaks have been classified as weepers, and most appear to be ID-initiated. This suggests that a large majority of issues with the buried safety related piping is and will continue to be ID-initiated.Structural Integrity Associates, Inc. (SI) has developed a Life Cycle Management (LCM) assessment approach that provides a method for quantitatively defining leaks, thinning, probability of at least one leak, etc. as a function of time. This can help plants more effectively plan timely inspections, repairs, and/or refurbishments, considering ID degradation. ID-initiated leaks and areas with significant wall loss discovered on AGP may be used as a primary indicator and benchmark to refine predictions on buried piping assets.One goal is to produce results that are amenable to financial analysis, based upon Net Present Value (NPV) computations for all options, including the option to “Do Nothing.” With NPV used to assess various mitigation options and future inspections/repairs/refurbishments, the long-term cost of the raw water piping assets can be more effectively planned and managed. The case study presented in this paper prioritizes segments based on their historical degradation, providing a framework that can be leveraged to identify the effectiveness of specific corrosion mitigation actions for the safety related service water systems.This presentation will provide an overview and insights into a new, first-of-a-kind and fully integrated, service water system integrity and asset management project approach.