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:
The objective of the internal flood scenario analysis is to identify the potential flood scenarios for each flood source by identifying flood propagation paths of water from the flood source to its RG 1.247, Page 26 accumulation point (e.g., pipe and cable penetrations, doors, stairwells, failure of doors or walls) for all POSs. Plant design features or operator actions that have the ability to terminate the flood are identified. The susceptibility of each SSC in a flood area to flood-induced mechanisms (e.g., submergence, spray, pipe whip, and jet impingement) is examined. Flood scenarios are developed by examining the potential for propagation and giving credit for flood mitigation. Flood scenarios can be eliminated on the basis of screening criteria. The screening criteria used are well defined and justified. All POSs should be evaluated for differences in the internal flood scenario analysis element. It is important that the flood sources and flood propagation paths consider the possible differences between POSs and possible temporary alignments that could impact the evaluation. These differences from at-power configurations may account for changes in flood pathways, in flood barrier locations and capabilities, in the location of SSCs, and additions of temporary features. The characteristics and attributes needed to achieve the objectives of the internal flood scenario analysis are as follows: • The following are identified and evaluated: o flood propagation paths for all POSs, o flood-mitigating plant design features (e.g., drains and sumps) and operator actions, and o the susceptibility of SSCs in each flood area to the different types of floods. • Well defined and justified screening criteria are used for the elimination of flood scenarios. • All POSs 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