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:
xcessive bending of the attached piping from differential thermal expan sion of the vessel could be a problem that required careful temperature control. Mager and others (Refs. 5 and 6) reported on re search to determine the extent of fracture toughness recovery as a function of annealing time and tempera ture for materials that are sensitive to neutron embrittlement. They concluded that excellent recov ery of all properties could be achieved by annealing at 850*F for 168 hours, and that the reembrittlement af ter annealing would follow the same trend as the pre annealing embrittlement rate. These reports also de scribe a thermal annealing procedure developed for field application. Additional research that includes data on irradiation-anneal-reirradiation property trends for reactor pressure vessel welds has been reported by Hawthorne and Hiser (Ref. 7). More recently*, Eason et al. performed analyses of existing data on annealing of irradiated pressure vessel steels using both mechanistic and statistical consider ations. Eason et al. also developed improved correla- 1.162-2 Is. K1 tion models for estimating Charpy upper-shelf energy and transition temperature after radiation and anneal ing. This work is reported in NUREG/CR-6327 (Ref. 8), and it provides the basis for equations for estimat >• ing recovery of fracture toughness following annealing (Section 3.1.3 of this regulatory guide). General guidance for inservice annealing may be found in ASTM Standard E 509-86 (Ref. 9). ASTM Standard E 509-86 contains general procedures for conducting an in-service thermal anneal of a reactor vessel and for demonstrating the effectiveness and de gree of recovery. ASTM Standard E 509-86 also pro vides direction for a post-anneal vessel radiation sur veillance program. CURRENT 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