Document: NRC Regulatory Guide
Document ID: a4944d20-ef6e-480b-a45d-14425bedd2e5
Document Type: regulatory_guide
Title: ASME Code Cases Not Approved for Use (Rev. 8)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2219/ML22196A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.193
CFR Part: 
CFR Title: 

Content:
application to both carbon and low-alloy steel materials. Use of this expression for low-alloy steel may be nonconservative because the constant is higher for low-alloy steel compared to carbon steel (0.702 versus 0.632). (4) The Code Case Fen expression is nonconservative for some environmental conditions compared to the new NRC expressions (i.e., for T less than 200 °C, strain rate equal to 0.001%/s, and dissolved oxygen values higher than 0.04 ppm). c. Stainless Steel Fatigue Curve: Code Case, Figure-2100-2, Figure-2100-2M, and Table-2100-2, define the design fatigue air curve for stainless steels. The Code Case fatigue curve matches the design fatigue air curve that is currently in Section III, Appendix I (2011 Addenda). The Code Case fatigue curve matches the stainless steel design fatigue air curve from the initial revision to NUREG/CR-6909 (which is the same curve the NRC intends to use in NUREG/CR-6909, Revision 1). However, item (d) below must also be considered when evaluating the adequacy of Fen usage factors calculated using the design curve. d. Stainless Steel Fen Expression: Equation (2) of the Code Case uses the stainless steel Fen expression from the initial revision to NUREG/CR-6909. This equation is different from the Fen expression that the NRC recently developed, and the equations for the transformed environmental parameters are different; therefore, the Fen equation may yield nonconservative values of Fen in cases that use the average temperature (see item (f)). e. Ni-Cr-Fe Steel: The same observations under item (c) applies for Ni-Cr-Fe steels because the stainless steel fatigue curve is used for Ni-Cr-Fe materials. Equation (3) of the Code Case uses the Ni-Cr-Fe steel Fen expression from the initial revision to NUREG/CR-6909. This equation is the same as the Fen expression recently developed by the NRC, but the equations for the transformed environmental parameters are different, and the Fen equation may yield nonconservative values of Fen