European contributions to environmental fatigue issues experimental research in France, Germany & Finland

Environmentally assisted fatigue (EAF) is at the centre of numerous discussions and conferences on fatigue around the world. The methodology proposed in NUREG/CR-6909 [1] is being applied in the USA for new builds and for license renewal per the RG 1.207 [2], but there is still room for a better understanding of all the effects involved and for fine-tuning of the methodology. A roadmap by EPRI lists areas where testing is recommended [3]. In Europe, research is going on and the accumulated results show that NUREG/CR-6909 is very conservative [4]-[10]. Applicability of the proposed design curve and the Fen factors were questioned in previous papers and alternative approaches have been developed [11]-[14]. This paper summarizes different experimental, analytical and practical approaches taken by four main players in the European nuclear industry and compares results with the NUREG/CR-6909 methodology. This joint discussion demonstrates that, although the approaches have been different, a common conclusion is reached: the NUREG/CR-6909 methodology can be improved.