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:
an overcooling transient. 1 All three of these categories should be discussed in this section. . 1. Procedures and/or the operators1 general knowledge can lead t o actions that improve the conditions associated with an overcooling event. Explanation should be included as to why i t i s perceived that this action would be taken. Where appropriate, these operator actions should be either included directly on the event trees or presented as separate operator action trees that can later be coupled w i t h the principal event trees. 2. Although the ORNL studies (Refs. 1, 2, and 3) did not include operator- initiated events or events aggravated by operator actions contrary to procedures, this category of events should also be examined as part of a plant-specific analysis. 3. The analyses should include a quantitative approximation of the PTS risk resulting from operator acts of commission. Also included should be the possibility that an operator could initiate or exacerbate some milder event into a more severe PTS-type event. Since there i s no generally accepted way t o perform such analyses, the approximation used by the licensee for this purpose should be discussed and justified for appl icabi 1 ity to this particular plant. The "confusion matrix" approach (Ref. 6) used i n human reliability analysis could provide an acceptable structure for identifying and analyzing these potential operator actions. I 3.4 Sequence Quantification Quantify the event trees by using identified initiating event frequencies, appropriate conditional probabilities associated with ttie success or failure of specific equipment operations, and success and failure probabilities asso- ciated with operator actions. Plant-specific data should be used whenever appropriate to define these probabilities, 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.