Document: NRC Regulatory Guide
Document ID: 2704425a-c58a-45c4-93ab-8761721c3e7a
Document Type: regulatory_guide
Title: Evaluation of Reactor Pressure Vessels with Charpy Upper-Shelf Energy Less Than 50 Ft-Lb
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740038.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.161
CFR Part: 
CFR Title: 

Content:
ivalent safety margins, or they may use any other methods, procedures, or selection of materials data and transients to demonstrate compliance with Appendix o to 10 CFR Part 50. If licensees choose to follow this regulatory guide, they must use the acceptance criteria, analysis methods, material properties, and selection of transients as described in this regulatory guide. The accep tance criteria are to be satisfied for each category of transients, namely, Service Load Levels A and B (normal and upset), Level C (emergenc), and Level D (faulted) conditions. These service load levels are described in Standard Review Plan 3.9.3 (Ref 11). Because of differences in acceptable outcome during the various sevice load levels, different criteria have been developed for Levels A and B, C, and D. 1.1 Level A and B Conditions When the upper-shelf Charpy energy of the base metal is less than 50 ft-lb, postulate both axial and circumferential interior flaws and use the toughness properties for the corre sponding orientation. For a weld with Charpy upper-shelf energy less than 50 fl-lb, postulate an interior surface flaw oriented along the weld of concern and orient the flaw plane in the radial direction. Postulate a semi-elliptical surface flaw with an aht = 0.25 and with an aspect ratio of 6-to-I surface length to flaw depth. A smaller flaw size may be used on an individual-case basis ifjustified. Two criteria must be satisfied as described below. The maximum accumulation pressure, discussed below, is the maximum pressure defined in the Over Pressure Protection Report that satisfies the requirement of Section III, NB-731 1(b), of the ASME Code (Re 12). 1.1.1 The crack driving force must be shown to be less than the material toughness as given by Equation 1: (1) where J,, is the J-integral value calculated for the postu lated flaw under pressure and thermal loading where the assumed pressure is 1.15 times the maximum accumulation pressure, with thermal loading using the