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:
on should be complete and comprehensive through consideration of the following: • All radiological sources at the plant (e.g., reactor cores, spent fuel, fuel reprocessing facilities for molten salt reactors) should be addressed, including accident scenarios that lead to a radioactive release from multiple radiological sources. • All internal and external hazards should be addressed. For licensing activities, a PRA for the seismic hazard group must always be developed; other hazards should also be included if they cannot be screened out with appropriate justification. Appendix B to this RG lists hazards to consider when developing the PRA. • All POSs (e.g., at-power and low-power and shutdown (LPSD) types of POSs) should be addressed. • The frequencies of event sequences should be developed based on the occurrence of an initiating event, evaluation of plant response, evaluation of releases of radioactive material, and the consequences that result from those releases (i.e., an NLWR PRA should address all levels of PRA analysis, analogous to Level 1, 2, and 3 PRAs for LWRs). Risk characterization for NLWRs is typically expressed by cumulative risk metrics or risk surrogates, commensurate with the purpose for developing the PRA and the role that the PRA plays in regulatory decision-making. The following are two common cumulative risk metrics, which can be directly compared to the quantitative health objectives (QHOs) stated in the Commission’s policy statement on “Safety Goals for the Operation of Nuclear Power Plants”: • Individual early fatality risk (IEFR): The risk of an early fatality to a biologically average individual (in terms of age and other risk factors) who resides within 1 mile of the site exclusion area boundary. If no individuals reside within 1 mile of the plant boundary, for evaluation purposes, an individual should be assumed to reside 1 mile from the site boundary. An accident may result in the release of a large quantity of