Status of the French methodology proposal for environmentally assisted fatigue assessment

Environmentally Assisted Fatigue is receiving nowadays an increased level of attention for new builds and also for installed bases which are currently having their lives extended to 60 years in various countries. To formally integrate these effects, some international codes have already proposed code cases. More particularly, the ASME code has based itself on the NUREG/CR-6909 [1] to elaborate the Code Case N-792 [2] and suggests a modification of the fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which is to be multiplied by the usual fatigue usage factor. In France, EDF and AREVA also aim at more explicitly integrating these effects in the RCC-M code. The initiative is technically supported by CEA and bases itself on international methodologies but also on results from French in-house testing campaigns [3] [4]. The approach is globally similar to the one in the ASME code: it will indeed consist in an update of the mean air and design fatigue curves as well as the calculation of an environmental penalty factor. Nevertheless, the methodologies differ in their detailed implementation, as was already hinted in previous papers discussing the French methodology [5] [6]. This paper is the sequel to the proposal already described in [7].