Document: NRC Regulatory Guide
Document ID: 5a810f5d-d35a-4bd8-bde7-205519300c40
Document Type: regulatory_guide
Title: Thermal Shock to Reactor Pressure Vessels
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1221/ML12216A018.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.2
CFR Part: 
CFR Title: 

Content:
n of potential irradiation effects in presently designed PWRs and BWRs, this de- gree of recovery of material toughness proper- ties combined with the potential for repeating the annealing process, if required, appears to be adequate to permit continued plant operation with the same reactor pressure vessel through- out plant lifetime. C. Regulatory Position To assure that the reactor pressure vessel will behave in a nonbrittle manner under loss of coolant conditions, the following program should be followed: 1. Data collection and research work on the properties of reactor pressure yes- 2.1 sel material should be continued in or- der to permit verification that expected material properties assure nonbrittle behavior of the reactor vessel through- out its lifetime under postulated acci- dent conditions. It is expected that this determination can be made within 5 years. 2. During the 5-year period necessary to develop the needed data, the potential reactor pressure vessel thermal shock problem which may result from emer- gency core cooling system operation need not be reviewed in individual cases unless significant changes in pres- ently approved core or reactor pres- sure vessel designs are proposed. 3. Should it be concluded that the margin of safety against reactor pressure ves- sel brittle failure due to emergency core cooling system operation at any time during vessel life is unacceptable, an engineering solution, such as an- nealing, could be applied to assure ade- quate recovery of the fracture tough- ness properties of the vessel material. In the meantime, applicants should out- line available engineering solutions and show that their designs do not preclude the use of such solutions. 2.2