Document: NUREG-0800
Document ID: e2737d9a-8e56-46cb-a97d-aaf62a442c6c
Document Type: srp
Title: PRESSURE-TEMPERATURE LIMITS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340637.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.3.2
CFR Part: 
CFR Title: 

Content:
ection Against Nonductile Failure," during heatup, cooldown, and test conditions. Appendix G to 10 CFR Part 50 also requires additional safety margins whenever the reactor core is critical (except for low-level physics tests). 2. Technical Bases Since many of the fracture toughness requirements for the ferritic materials in the pressure-retaining components were not'required at the time some of the reactor facilities were designed and constructed, the Materials Engineering Branch Technical Position MTEB 5-2, "Fracture Toughness Requirements," describe procedures for making estimates and assumptions on the fracture toughness properties of materials in the older plants. Calculations are required, and an evaluation is made by the reviewer to show compliance with the regulations and to show an adequate margin of 5.3.2-2 Rev. 1 - July 1981 quality and safety for the facility. When it has been determined that certain requirements of Appendices G or H have not been strictly complied with by these older plants, and when it has been determined that an equivalent level of quality and safety, as required by the regulations exist, then exemption to the specific requirements of these appendices will be granted by the Commission. a. The principles of linear elastic fracture mechanics (LEFM) are used to determine safe operational conditions. The basic parameter of LEFM is the stress intensity factor, KI, which is a function of the stress state and flaw configuration. An analytical method is used to determine the effects of real or postulated flaws. The minimum KI that can cause failure is defined as the critical stress intensity factor, KIC, and is the material parameter used in this method. The KIC of the material is either directly measured as a function of temperature, or is conservatively estimated, using information from other fracture toughness tests. b. The Code specifies the maximum KIC, as a function of temperature, that can be assumed for the specific material, based on