Implementation of the EPRI Guidelines to Fatigue Analyses of Primary Circuit Components: Challenges and Recommendations in the Framework of Practical Application

The influence of LWR coolant environment to the lifetime of materials has been discussed recent years. Nowadays the environmentally assisted fatigue (EAF) is under consideration in Codes and Standards like ASME by formula calculation and in the German KTA Rules (e.g. KTA No. 3201.2 and 3201.4) in addition by means of so called attention thresholds.Basic calculation procedures in terms of quantifying the influence of LWR coolant environment by the so called Fen-factor were proposed in NUREG CR-6909 in 2007. Since this report the set of formulas have been adapted several times (e.g. in ANL-LWRS47-2011) and further changes in set of formulas are likely to occur. Subsequently a revision of the NUREG CR-6909 report is taking place incorporating recent changes.Within the EPRI 2012 Technical Report “Guidelines for Addressing Environmental Effects in Fatigue Usage Calculations” some practical recommendations for the application of the EAF to real components are stated. In this report EPRI presented the calculation of sample problems in combination with sample transients carried out by the participants and verifying the applicability of the proposed approaches. However, the EPRI guideline provides a set of tools taking environmentally assisted fatigue into account. This guidance figures out to be quite helpful on one hand, but incorporates some challenges in terms of practical application on the other hand. Additionally, the EPRI Report gives no clear advice which specific combination of calculation methods to apply finally.Within this publication the procedures proposed in the EPRI guideline will be applied to existing numerical approaches being published. Challenges when applying the methods defined in the EPRI guideline will be identified and solutions will be given. Additionally, recommendations will be stated based on the proposed procedures in terms of practical application especially in context of calculations for fatigue relevant primary circuit components.Copyright © 2014 by ASME