Document: NRC Regulatory Guide
Document ID: da2e0703-3488-44b0-b6d0-089aac7cae3d
Document Type: regulatory_guide
Title: Format and Content of Plant-Specific Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water Reactors
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740028.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.154
CFR Part: 
CFR Title: 

Content:
including appropriately adjusted simulator studies. This should be supplemented by vendor-specific or PWR- generic data bases when plant-specific 'data do not appear to provide an adequate data base. Reference 7 includes guidance about treatment of generic and plant- specific data. Its appendices include an updated generic data base that should be used. Identify by specific reference or provide in appendices all the reliability data used as input to quantify the event sequences. An explanation should be suppl ied as to how the data were derived for each data point. 3.4.1 Initiating Events Initiating event frequencies should be developed based on the number of observed events within selected periods of operation for similar plants under consideration. If no failures have been observed and no othe-r information is available with which to estimate a probability, a standard statistical method such as the Poisson distribution can be used to determine a probability, or the technique described in Appendix B to Reference 3 for estimating plant-specific initiating event frequencies can be used. For some initiators, it may be neces- sary to estimate the frequency of events in a particular operating mode, e. g. , hot zero power. The data should be researched to identify trends associated with the occurrence of the event and the operating mode. In addition, the initiator itself should be examined to identify physical conditions that might favor failure iti one mode rather than another. If this examination reveals no evidence of correlation between frequency and operating mode, the fraction of time spent in each operating mode can be used as a weighting factor. 3.4.2 Equipment Fai 1 ures Following each initiating event, certain components are designed to perform in a defined manner. Failure of a component to perform its required function could lead to PTS considerations. Thus, it is necessary to assign a failure and successful operation probability for each component on a