Document: NRC Regulatory Guide
Document ID: 22ccfd5e-c5d8-4615-a02c-32369aa9f533
Document Type: regulatory_guide
Title: Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1930/ML19308B636.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.200
CFR Part: 
CFR Title: 

Content:
tions of the hazard groups to the various risk metrics. Therefore, the sources of model uncertainty are identified and their impact on the results analyzed for each hazard group individually, so that, when it is necessary to combine the PRA results, the overall results can be characterized appropriately. The sensitivity of the model results to key assumptions and sources of uncertainty from modeling assumptions, model boundary conditions, and other assumptions is evaluated. Such evaluations should include sensitivity analyses to look at key assumptions both individually and in logical combinations. The combinations analyzed are chosen to account for interactions among the variables. NUREG-1855 provides guidance on the treatment of uncertainties associated with PRA as well as guidelines regarding defining, identifying, and characterizing different sources of uncertainty. Table 12 summarizes the characteristics and attributes needed for the technical elements of interpretation of results. Table 12. Summary of Technical Characteristics and Attributes for Interpretation of Level 1 and Level 2 PRA Results Element Technical Characteristics and Attributes Level 1 PRA Interpretation of Results • Identification of the significant contributors to CDF (hazard groups, initiating events, specific hazard plant damage states, accident sequences, equipment failures and human errors) • Identification of sources of uncertainty and their potential impact on the PRA model • Understanding of the impact of the assumptions on the CDF and the identification of the accident sequence and their contributors Level 2 PRA Interpretation of Results • Identification of the contributors to containment failure, resulting source terms, LERF and LRF • Identification of sources of uncertainty and their impact on the PRA model • Understanding of the impact of the assumptions on Level 2 results Technical Elements for PRA Documentation The documentation of the PRA model provides the necessary