Document: NRC Regulatory Guide
Document ID: 5f4d6577-6c2a-473a-9a76-4033a95dba4c
Document Type: regulatory_guide
Title: Radiation Embrittlement of Reactor Vessel Materials (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740284.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.99
CFR Part: 
CFR Title: 

Content:
uation 2 for ARTNDT (in Regulatory Position 1.1 of this guide) is contained in publications by G. L. Guthrie (Ref. 2) and G. R. Odette et al. (Ref. 3). Both of these papers used surveillance data from commercial power reactors. The bases for their regression correlations were different in that Odette made greater use of physical models of radiation embrittlement. Yet, the two papers contain similar recommendations: (1) separate correla- tion functions should be used for weld and base metal, (2) the func- tion should be the product of a chemistry factor and a tluence factor, (3) the parameters in the chemistry factor should be the elements copper and nickel, and (4) the tluence factor should provide a trend curve slope of about 0.25 to 0.30 on log-log paper at 1019 n/cm2 (E > 1 MeV), steeper at low tluences and flatter at high fluences. Regulatory Position 1. 1 is a blend of the correlation functions presented by these authors. Some test reactor data were used as a guide in establishing a cutoff for the chemistry factor for low- copper materials. The data base for Regulatory Position 1.2 is that given by Spencer H. Bush (Ref. 4). The measure of fluence used in this guide is the number of neutrons per square centimeter having energies greater than 1 million electron volts (E > 1 Me V). The differences in energy spectra at the surveillance capsule and the vessel inner surface locations do not appear to be great enough to warrant the use of a damage func- tion such as displacements per atom (dpa) (Ref. 5) in the analysis of the surveillance data base (Ref. 6). However, the neutron energy spectrum does change significantly with location in the vessel wall; hence for calculating the attenua- tion of radiation embrittlement through the vessel wall, it is necessary to use a damage function to determine ARTNDT versus radial distance into the wall. The most widely accepted damage func- tion at this time is dpa, and the attenuation formula (Equation 3) given in Regulatory