Document: NRC Regulatory Guide
Document ID: 7c9a00a8-375c-4641-bc1b-762a663a96d6
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:
E Code developers applied a margin of two on strain (or stress) and a margin of twenty on cyclic life to develop design fatigue curves that accounted for variations in materials, size, surface finish, data scatter, and environmental effects (including temperature differences between specimen test conditions and reactor operating experience). However, the developers lacked sufficient data to explicitly evaluate and account for fatigue life degradation attributable to component exposure to aqueous coolants. Reflecting this circumstance, Paragraph NB-3121, “Corrosion,” in Section III of the ASME Code states that the design fatigue curves did not include tests in the presence of corrosive environments that might accelerate fatigue failure. Paragraph NB-3121 further states that provisions for the presence of corrosive environments that might accelerate fatigue failure shall be included in the design or specified life of components. More recent fatigue-test data from the United States (including the results of NRC research activities), Japan, and elsewhere show that LWR coolant environments can have a significant impact on the fatigue lives of components made from carbon, low-alloy, austenitic stainless (both wrought and cast), and nickel-chromium-iron (Ni-Cr-Fe) alloy steels and welds. In the 1990s, as a part of NRC research activities on fatigue, the staff evaluated two distinct methods for incorporating LWR environmental effects into the fatigue analysis of ASME Code, Class 1 components. The first method involved developing new fatigue curves that were applicable to LWR environments. Given that the fatigue life of ASME Code, Class 1 components in LWR coolant environments is a function of several parameters, this method necessitated the development of several fatigue curves to address potential parameter variations. Alternatively, a single bounding fatigue curve could be developed, but this approach might be overly conservative for most applications. The second