Environmentally Assisted Fatigue Screening Process Application

Abstract

In the frame of extension of nuclear plant operation life or new nuclear reactor construction, environmentally assisted fatigue (EAF) assessment is required by many regulators to be considered for pressure boundary components. The methodology of EAF assessment, through EAF cumulative usage factor (CUFen) calculations, has been integrated in RPP n°3 (Rule in Probationary Phase) of French RCC-M code [2]. This methodology is applicable to sentinel locations of Class 1 components made of austenitic SS that have been identified in advance. In order to minimize final number of sentinel locations for considering EAF effects, EAF screening methods are presented in EPRI report [3], which allow to rank the CUFen values and give a list of sentinel locations that assume to cover other locations within each thermal zone. In particular, the EDF Screening method based on RCC-M code using Fenintegrated concept has been integrated in revision 1 of EPRI report. The EDF Screening method [5] was built for the fourth ten-year visit of the 900 MWe plants, for which stress reports were updated and contain detailed information of fatigue analyses. It is not applicable for locations without an explicit fatigue analysis or without any pair loads information. In this paper, a new screening method is proposed based on Fenintegrated concept and RCC-M code for austenitic SS Class 1 components and piping. Environmental fatigue factor (Fen) is estimated by a simple process for each location. The CUFen is determined using Fen and Fenintegrated. For locations without an explicit cumulative usage factor (CUF) calculation, transient combinations will be estimated according to the analytical method described in B3600 of RCC-M for piping. Finally, the sentinel locations identified will be compared to those selected in EPRI report.