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:
3 in Mol, Belgium, in 1984 (Ref. 2). Both of these reactors operated at temperatures low enough to permit "wet annealing" at a temperature of 650°F using the reactor coolant pumps as the heat source. In addition, at least 12 Russian-designed VVER-440 PWRs, which operate at conditions similar to U.S. PWRs, have been an nealed in Russia and Eastern Europe at temperatures of approximately 850*F, using dry air and radiant heaters as the heat source. Details of the thermal an nealing of the Novovoronezh Unit 3 have been re ported (Ref. 3) by a U.S. delegation that witnessed the operation. CURRENT STATE OF KNOWLEDGE ON THERMAL ANNEALING A significant amount of information has been re ported in the literature on thermal annealing and on the effects of thermal annealing variables (e.g., tem perature, time, materials chemistry, fluence levels), on the recovery of toughness properties. Server (Ref. 4) summarized the state of knowledge, as of 1985, for in-place thermal annealing of commercial reactor pres sure vessels. He reviewed data on annealing recovery and reirradiation effects for high-copper welds and concluded that significant recovery occurs for anneal ing at 850*F for both the transition temperature shift (ARTNDT) and reduction in Charpy upper-shelf ener gy. He also reviewed engineering studies and con cluded that annealing of U.S. reactors at 850*F is fea sible using existing commercial heat treating methods, but that plant-specific engineering problems would need to be resolved. Server (Ref. 4) also performed a thermal and structural analysis for a typical PWR vessel annealed at 850 0 F, which predicted that vessel dimen sional stability would be maintained and that post anneal residual stresses would not be significant. How ever, Server's results indicated that excessive 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