Document: NRC Regulatory Guide
Document ID: 40fb588c-37f6-474f-b12a-d7be81beefe5
Document Type: regulatory_guide
Title: Guidelines for Evaluating Fatigue Analyses Incorporating the Life Reduction of Metal Components Due to the Effects of the Light-Water Reactor Environment for New Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1417/ML14171A584.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.207
CFR Part: 
CFR Title: 

Content:
simulations to develop fatigue design curves using the “95/95 criterion.” In other words, the curves should provide 95% confidence that the fatigue life of 95% of the population of laboratory test specimens will be greater than that predicted by the design curves. The NRC staff deems this criterion acceptable because the NRC staff bases the fatigue design curves on crack initiation, rather than component failure or through-wall crack leakage, and, therefore, additional margin exists between crack initiation and actual component failure or leakage. The results of the Monte Carlo simulations indicated that for carbon, low-alloy, austenitic stainless, and Ni-Cr-Fe alloy steels, the current ASME Code procedure of adjusting the mean test data by a factor of twenty for cyclic life is conservative compared to the 95/95 criterion. The NRC staff’s results indicated that a factor of ten to twelve for cyclic life was sufficient to satisfy the 95/95 criterion for these materials. Figures 36, 37, and 49 of Revision 1 of NUREG/CR-6909 present the resulting new fatigue design curves using margins of twelve for cyclic life and two for strain (whichever is more conservative) for carbon steels, low-alloy steels, and austenitic stainless steels, respectively. This guide uses these new air design curves; thus, an applicant or licensee that chooses to adopt the procedure discussed in this guide to determine the fatigue lives of carbon, low-alloy, austenitic stainless, and Ni-Cr-Fe alloy steels should use the air design curves in Revision 1 of NUREG/CR-6909. The fatigue design curves for carbon and low-alloy steels and austenitic stainless steels in Section III of the 2013 Edition of the ASME Code may also be used with the procedure in this guide to determine the fatigue lives of those materials, because their use will yield the same or more conservative results. Fen calculations for carbon, low-alloy, austenitic stainless, and Ni-Cr-Fe alloy steels need only consider the types of