Document: NRC Regulatory Guide
Document ID: a2b67b51-f5fe-4c86-a879-f0e439601f7f
Document Type: regulatory_guide
Title: Format and Content of Report for Thermal Annealing of Reactor Pressure Vessels
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740052.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.162
CFR Part: 
CFR Title: 

Content:
T REGULATORY REQUIREMENTS FOR FRACTURE TOUGHNESS OF VESSELS Fracture toughness requirements for light-water cooled reactor pressure vessels are addressed in sever al regulations. Appendix G, "Fracture Toughness Re quirements," to 10 CFR Part 50 provides the fracture toughness requirements for vessels during normal op eration and anticipated accident conditions. Appendix G also permits the use of thermal annealing to restore fracture toughness degraded by neutron radiation when embrittlement degrades mechanical properties to such an extent that adequate margins of safety cannot be demonstrated during operation. Appendix H, "Reactor Vessel Material Surveillance Program Re quirements," to 10 CFR Part 50 requires surveillance programs to monitor irradiation embrittlement of reac tor vessel beltline materials. The pressurized thermal shock (PTS) rule, 10 CFR 50.61, establishes screening criteria for embrittlement beyond which the plant may not operate without further justification. The application of these regulations in the late 1980s and early 1990s demonstrated a need for clarifi cation and improved guidance. The NRC review of the reactor pressure vessel integrity of the Yankee Nuclear Power Station highlighted the need for such changes and resulted in a detailed plan described in SECY-91-333 (Ref. 10) and SECY-92-283 (Ref. 11). To implement this plan, a proposed rule to amend the regulations was issued on October 4, 1994 (59 FR 50513). This rule was issued in final form on Decem ber 19, 1995 (60 FR 65456). The rule includes a new § 50.66, "Requirements for Thermal Annealing of the Reactor Pressure Vessel," which sets forth the NRC's requirements for annealing of reactor pressure vessels. Also, changes were made to both Appendix G and the PTS rule to reference the thermal annealing require ments in § 50.66, as an option for reducing embrittle ment when the toughness requirements of those rules cannot otherwise be met. The thermal annealing rule, 10 CFR 50.66, per