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:
er limiting values given in the material specifications to which the vessel was built may be used. If not available, conservative estimates (mean plus one standard deviation) based on generic data may be used if justification is provided. If there is no information available, 0.35% copper and 1.0% nickel should be assumed. The neutron fluence at any depth in the vessel wall, f (1019 n/cm2, E > 1 MeV), is determined as follows: f = fsurf (e -0.24x) (3) where fsurf (1019 n/cm2, E > 1 MeV) is the calculated value of the neutron fluence at the inner wetted surface of the vessel at the location of the postulated defect, and x (in inches) is the depth into the vessel wall measured from the vessel inner (wetted) surface. Alternatively, if dpa calculations are made as part of the fluence analysis, the ratio of dpa at the depth in question to dpa at the inner surface may be substituted for the exponential attenuation factor in Equation 3. The fluence factor, f0.28 - 0.10 log f, is determined by calcula- tion or from Figure 1. ''Margin'' is the quantity, °F, that is to be added to obtain con- servative, upper-bound values of adjusted reference temperature for the calculations required by Appendix G to 10 CPR Part 50. Margin = 2 V a2 + a 2 I A (4) "The class for estimating initial RTNDT is generally determined, for the welds with which this guide is concerned, by the type of welding flux (Linde 80 or other); for base metal, by the ASTM Standard Specification. Here, 01 is the standard deviation for the initial RTNDT· If a measured value of initial RTNDT for the material in question is available, OJ is to be estimated from the precision of the test method. If not, and generic mean values for that class of material are used, OJ is the standard deviation obtained from the set of data used to establish the mean. The standard deviation for ARTNDT, a A, is 28 °F for welds and 17 °F for base metal, except that OA, need not exceed 0.50 times the mean value of ARTNDT· 1.2 Charpy