Document: NUREG-0800
Document ID: 7916b088-fb90-4163-84fe-027bd315bcc5
Document Type: srp
Title: REVIEW OF RISK INFORMATION USED TO SUPPORT PERMANENT PLANT-
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0717/ML071700658.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.2
CFR Part: 
CFR Title: 

Content:
rator dependencies (functional, operational, and procedural), especially for those components affected by the application. A review of the licensee's failure modes and effects analysis and a review of plant operating and emergency procedures will be useful for this purpose. The usefulness of PRA results in risk-informed regulation is dependent on the level of resolution of the modeled SSCs. A component-level resolution provides insights at the component level. However, if a PRA is performed at a system or train level, the insights of the PRA will be limited to that level unless it can be demonstrated that component-level insights can be bounded by, or deduced from, system- or train-level effects. The direct application of PRA results will therefore be limited to those SSCs that are explicitly modeled as part of the PRA basic events. Insights for SSCs that are implicitly modeled (e.g., screened out, assumed not important) are only to be used after additional consideration of the effects of the proposed change on PRA assumptions, screening analyses, and boundary conditions. Specifically, the following relationships exist between the level of detail in the modeling of each SSC and the conclusions that can be drawn from the PRA: • If the SSCs are modeled at the basic event level, i.e., each SSC is represented by a basic event (or sometimes, more than one if different failure modes are modeled), risk insights from the PRA can be applied directly to the modeled component as long as the effects of the change are appropriately considered. • If the SSCs are included within the boundaries of other components (e.g., the governor and throttle valves being included in the pump boundary), or if they are included in "black boxes" or modules within the PRA model, or if they are modeled as part of the calculation of human error probabilities (HEPs) in recovery actions, risk insights from the PRA can be applied if the effects of the application can be mapped onto the events