Document: NUREG-0800
Document ID: 26aca061-b0de-4983-bbca-3fccb00afc2f
Document Type: srp
Title: PRESSURE-TEMPERATURE LIMITS AND PRESSURIZED THERMAL SHOCK1
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070431.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.3.2
CFR Part: 
CFR Title: 

Content:
rgin of 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 as described in 10 CFR 50.60 and 10 CFR 50, Appendix G, paragraph III.A . 19 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, K , which is a function of the stress state and flaw configuration. An I analytical method is used to determine the effects of real or postulated flaws. The minimum K that can cause failure is defined as the critical stress intensity factor, I K , and is the material parameter used in this method. The K of the material is Ic Ic 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 K , as a function of temperature, that can be Ic assumed for the specific material, based on results of tests on the material used. This value is called K , reference stress intensity factor. The Code also IRa 20 provides rules for calculating K , including definitions of postulated flaws, and I specifies the safety factors to be applied. The acceptance criterion is that the K of the material must always be higher than the K calculated. IRa I 21 5.3.2-5 DRAFT Rev. 2 - April 1996 c. Direct measurement of the K as a function of temperature is expensive and time Ic consuming and requires more sample material than is usually available. Correlations between the K determined directly and results of simpler fracture Ic toughness tests are not exact, but may be used if appropriate allowances are made for variations in material behavior and data