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:
U.S. NUCLEAR REGULATORY COMMISSION Revision 2 May 1988 REGULATORY GUIDE OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 1.99 (Task ME 305-41 RADIATION EMBRITTLEMENT OF REACTOR VESSEL MATERIALS A. INTRODUCTION General Design Criterion 31, "Fracture Prevention of Reactor Coolant Pressure Boundary,'' of Appendix A, ''General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires, in part, that the reactor coolant pressure boundary be designed with sufficient margin to ensure that, when stressed under operating, maintenance, testing, and postulated accident conditions, (1) the boundary behaves in a nonbrittle manner and (2) the probability of rapidly propagating fracture is minimized. General Design Criterion 31 also requires that the design reflect the uncertainties in determining the effects of irradiation on material properties. Appendix G, "Fracture Toughness Requirements," and Appendix H, "Reactor Vessel Material Surveillance Program Requirements," which implement, in part, Criterion 31, necessitate the calculation of changes in fracture toughness of reactor vessel materials caused by neutron radiation throughout the service life. This guide describes general procedures acceptable to the NRC staff for calculating the effects of neutron radiation embrittlement of the low-alloy steels currently used for light-water-cooled reactor vessels. The calculative procedures given in Regulatory Position 1.1 of this guide are not the same as those given in the Pressurized Thermal Shock rule(§ 50.61, "Fracture Toughness Requirements for Pro- tection Against Pressurized Thermal Shock Events," of 10 CFR Part 50) for calculating RTPTS, the reference temperature that is to be compared to the screening criterion given in the rule. The information on which this Revision 2 is based may also affect the basis for the PTS rule. The staff is presently considering whether to propose a change to § 50.61.