Fatigue is identified as a significant degradation mode that affects nuclear power plants world-wide. Recent research on the interaction between fatigue degradation and the influence of PWR environment has caused international concern and triggered numerous research programs \[1\]. In this context, several codes & standards, including the RCC-M code, have included some technical mandatory or non-mandatory sections to address the issue. In RCC-M, this is compiled in the Rules in Probation Phase N°2 and 3 \[2\].  

Due to the novelty of these rules, there is room for improvement for their specific and practical implementation. AFCEN has hence launched a benchmark exercise at the end of 2019 to help increase the quality and uniform application of these rules.

Part 1 of this paper \[3\]states that EDF and CNNC/NPIC have launched an effort to benchmark their respective codes on fatigue calculation including the EAF algorithm. In the second part of the benchmark, the two companies started the code comparison based on a benchmark case provided by AFCEN.

As stated previously, the 2016 edition of RCC-M code integrates the modifications made to the Code in Probation Phase 2 and 3 (RPP) \[2\], which respectively modify the fatigue design curve for austenitic stainless steels and Nickel base alloys, as well as integrate environmental effects in the fatigue evaluation for austenitic stainless steel components. In this paper, a comparison between RCC-M RPP and NUREG/CR-6909 rev.1 \[3\] is proposed. The comparison focuses on the technical details of the strain rate calculation and transient combination method.

The cumulative fatigue usage factor with or without considering EAF according to RCC-M RPP#2 and RPP #3 is given by EDF, using code_aster and its POST_RCCM operator. CNNC/NPIC, using its in-house code FAC_NPIC, provides multiple sets of results including cumulative fatigue usage factors with or without considering EAF according to RCC-M RPP and NUREG CR/6909 rev. 1. Comparison of different methods for the selection of peak and valleys points, Sn and F~en~ values are also presented. Differences in the algorithms of the two codes are also discussed.

References

\[1\]    NUREG/CR-6909 rev. 1, "Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials", O.K. Chopra and W.J. Shack

\[2\]    RPP n°2 & 3, RCC-M, AFCEN

\[3\]    PVP2019-93242, Hai XIE, Xuejiao Shao and Han LIU, " FATIGUE BENCHMARK COMPARISON EFFORT BETWEEN CODE_ASTER AND CNNC/NPIC SOFTWARE – PART 1".

\[4\]    PVP2016-63127, S. Courtin et al., “Modifications of the 2016 Edition of the RCC-M code to account for EAF.”


Fatigue Benchmark Comparison Effort Between Code_aster and Cnnc/npic Software \u2013 Part 2

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Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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