The conservatism of the austenitic stainless steel fatigue design curve has been severely questioned since the release of the NUREG/CR-6909 document [1] where a new methodology to assess environmentally assisted fatigue (EAF), including also a new in-air fatigue design curve, have been proposed. In the same way, the ASME Code Case N-792 [2] suggests calculating EAF usage factors via the multiplication of the in-air fatigue usage factors by Fen penalty factors, this resulting in a significant increase of these parameters.

In this context, AREVA NP SAS has performed, for several years, its own Pressurized Water Reactor (PWR) Low Cycle Fatigue (LCF) test program to better identify environmental effects in representative industrial conditions [3]. Among others, these experimental works have pointed out the over-conservatism of the NUREG/CR-6909 design approach. From these results, AREVA NP SAS has developed an alternative EAF assessment method which has been approved by the Finnish Nuclear Safety Authority [4]. This paper proposes to give an overview of this approach and to illustrate it on an EAF EPRI sample problem [5].

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