Fatigue is identified as a significant degradation mode that affects nuclear power plants world-wide. Several international codes and standards (ASME, RCC-M, JSME, etc...) offer rules to predict its damaging effect on the locations of the various components of an NPP. These rules, which ensure conservatism and safe operation, have grown in complexity over the years because they have integrated R&D results showing aggravating effects that were not included in the original analyses (such as Environmental Assisted Fatigue) but also because an economically viable design of components has required optimization and refinement of mechanical assessment methods.
CNNC/NPIC has been following carefully the recent evolutions in the fatigue rules and has today finalized an in-house software enabling the evaluation of fatigue per ASME and RCC-M rules, with integration of environmental effects.
On the other hand, EDF has been developing since 1989 its own in-house FEA code baptizedCode_Aster that is included in the Salome-Meca mechanical package. Salome-Meca is open-access and can be used freely by international users. Within Code_Aster, the fatigue postprocessor offers a span of criteria (Dang Van, Stress Intensity, etc...) to pick and choose from and even offers the possibility to make up owns one fatigue criteria. It also offers the possibility to post-process fatigue according to the RCC-M rules (POST_RCCM operator). It has been recently updated to perform industrial calculations integrating environmental fatigue.
Both entities have come to agree that validating a fatigue computer code is not an easy task. On the one hand, the full validation using hand calculations would be a highly tedious effort, given the technicality and the multiple choices to make along the various steps of the fatigue analysis. On the other hand, there are no experiments today which enable to directly lead a benchmark calculation to validate fatigue numerical results.
In consequence, an accepted way of validating a code is to perform a benchmark analysis against another industrial fatigue code. CNNC/NPIC and EDF R&D China have therefore launched an effort to benchmark their respective codes, with the final objective of progressing together towards safe structural assessment practical methods for their power plants components.