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:
e 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 function, relative risk-significant event sequence or event sequence family, relative risk-significant SSC or HFE), accounting for both the frequency and consequences of modeled event sequences. • If the application can be adequately supported by comparison of risk metrics to fixed targets, the analysis defines and justifies the selection of criteria used to establish the absolute risk significance of PRA model elements, accounting for both the frequency and consequences of modeled event sequences. • The uncertainties related to the risk-significance criteria are identified and characterized. The objective of expressing overall risk in terms of appropriate risk metrics is to provide a vehicle by which risk contributions from multiple reactors and other radiological sources can be integrated. The risk metrics used should be consistent with the selected risk-significance criteria and the intended application. The characteristics and attributes needed to achieve the objectives of expressing overall risk in terms of appropriate risk metrics are as follows: • Information on event sequences and event sequence families is compiled from the event sequence quantification (ESQ) and consequence quantification (RCQ) tasks. • The integrated risk results are calculated using the risk metric(s) previously defined and event sequences and event sequence families previously compiled. • Potential differences in level of detail, degree of conservatism, and realism are identified when integrating results for different radiological sources, hazards, or POSs. • Risk contributions from all sources of radioactive material considered and analyzed in the PRA are included within the scope of the PRA. • Risk-significant contributors are identified to develop insights from the PRA.