Document: NRC Regulatory Guide
Document ID: cde52d5a-adf9-49be-9d1f-59449dfca895
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
k Integration Probabilistic Risk Assessment Element This section identifies the objectives and the characteristics and attributes of the risk integration PRA element for an NLWR PRA that addresses all radiological sources, all hazards, all POSs, and all levels of PRA analysis. The objectives of the risk integration PRA element are to develop criteria used to determine risk significance, to express overall risk in terms of appropriate risk metrics, and to characterize and quantify the uncertainty associated with the calculated risk metrics. The objective of determining risk-significance criteria is to identify and justify the criteria by which the risk significance is established for PRA elements such as an event sequence, event sequence families, SSCs, and basic events modeled in the PRA. These risk-significance criteria should be defined consistent with and supportive of the intended application. As part of determining risk-significance criteria, technology-inclusive consequence metrics (e.g., radiological doses, health effects to public) or RG 1.247, Page 50 risk surrogates (e.g., LRF) are used. At a minimum, relative risk-significance criteria should be used to develop the PRA, including but not limited to Fussell-Vesely or Birnbaum importance measures, unless otherwise justified. The characteristics and attributes needed to achieve the objectives of determining risk-significance criteria are as follows: • The analysis defines consequence metrics (e.g., person-rem, early fatalities, latent health effects, site boundary dose, quantity of radioactive material release) or risk surrogates (e.g., LRF) that allow integration of risks from multiple sources and that support the intended application. • If the application involves calculation of a PRA baseline risk, the analysis defines and justifies the selection of criteria for establishing the relative risk significance of PRA model elements (e.g., relative risk-significant basic event, relative risk-significant