Challenges Associated With License Renewal Fatigue Evaluations for an Older-Vintage BWR Plant: Part 2

The Pilgrim Nuclear Power Station (PNPS) License Renewal Application (LRA) was submitted to the NRC in January 2006. As a part of the LRA submittal, Entergy committed to manage the aging effects of the reactor coolant environment on fatigue usage during the extended period of operation. As a part of PNPS’s aging management strategy, fatigue analysis was performed for 60-years of operation including EAF. This document provides some background information on the PNPS fatigue analysis, a summary of related information contained in the LRA submitted for NRC review and the specific actions taken to address the LRA commitments. A previous paper (PVP2010-25329) was prepared to provide an example of efforts expended to demonstrate long-term acceptability for license renewal where additional margins are required for PNPS Nuclear Power Station. The intent was to educate the reader on the efforts involved, the vast array of input that is needed and the possible hurdles that may be encountered for the validation and re-evaluation of Class 1 component fatigue for license renewal. The previous PVP paper discussed the foundation aspects necessary to prepare a refined fatigue evaluation with environmental affects for the plant. These include plant history, B31.1 piping analyses, environmental considerations, transient history, design specification and refined nozzle evaluations. The present paper discusses the importance of laying the appropriate foundation in the context of the final results that were obtained. It provides additional background information and actions taken to address the license renewal commitments and summarizes detailed results.