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:
rvatively 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 results of tests on the material used. This value is called KIR, reference stress intensity factor. The Code also provides rules for calculat- ing KI, including definitions of postulated flaws, and specifies the safety factors to be applied. The acceptance criterion is that the KIR of the material must always be higher than the KI calculated. c. Direct measurement of the KIC as a function of temperature is expensive and time consuming and requires more sample material than is usually available. Correlations between the KIC determined directly and results of simpler fracture toughness tests are not exact, but may be used if appropriate allowances are made for variations in material behavior and data scatter. The Code gives values of KIR as a function of temperature relative to a conservative determination of the reference temperature of the material. This reference temperature, RTNDT, is determined for the ferritic materials of components for which operating and testing limit curves must be calculated. The effects of radiation on the fracture toughness of the material in the beltline region of the reactor vessel is accounted for by adjusting the RTNDT of the affected material upward. The amount of upward shift depends on the composition of the steel (especially its copper and phosphorous content), and the neutron fluence. Conservative predictions of the effect of radiation on the RTNDT based on data in Regulatory Guide 1.99, are factored into the original limit curves. The continued conservatism of these predictions throughout plant life is verified by a mandatory material surveillance program described in Appendix H of 10 CFR Part 50. d. The Code specifies the stress components that must be used for the KI calculations, and the factors that must be applied to each to