Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
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:
s should be evaluated in the internal flood scenario analysis element. • Differences in the POS plant configuration and propagation pathways should be considered. The objective of the internal flood scenario delineation and quantification is to provide an estimation of the source terms and the radiological consequences of the plant that includes internal floods. The frequency of flood-induced initiating events that represent the design, operation, and experience of the plant is quantified. The internal events PRA is modified and the internal flood event sequences are quantified to (1) modify event sequence models to address flood phenomena, (2) perform necessary calculations to determine success criteria for flood mitigation, (3) perform parameter estimation analysis to include flood as a failure mode, (4) perform HRA to account for performance-shaping factors that are attributable to flooding, and (5) quantify internal flood source terms and radiological consequences. All POSs should be evaluated for differences in the internal flood scenario delineation and quantification analysis element. The characteristics and attributes needed to achieve the objectives of the internal flood scenario delineation and quantification are as follows: • Flood-induced initiating events are identified and grouped on the basis of a structured and systematic process for all POSs. • Flood-initiating event frequencies are estimated. • The internal events PRA is modified to account for flooding effects, including uncertainties. • The uncertainties in the internal flood PRA for a POS are characterized. The potential impact of sources of model uncertainty and related assumptions on the results are justified. • Source terms and radiological consequences for chosen flood sequences are estimated. • Well defined and justified screening criteria are used for the elimination of flood scenarios. RG 1.247, Page 27 C.1.3.9 Internal Fire Probabilistic Risk Assessment Element This section