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:
mptions include those that are identified or included in virtual layouts of the plant. All POSs should be evaluated for differences in the external flood fragility analysis PRA analysis element. It is important that the walkdowns evaluate the differences between the different POSs that impact the fragility analysis. The fragility analysis may need to be modified for LPSD types of POSs to account for changes compared to configurations for at-power types of POSs including but not limited to changes in flood pathways, in the location of SSCs, in the radioactive or hazardous material inventory in SSCs, or both, and addition of temporary features. The characteristics and attributes needed to achieve the objectives of an external flood fragility analysis are as follows: • The flood fragility estimate— o is plant specific, o is realistic, and o includes all SSCs that are involved in event sequences for each POS modeled in the external flooding PRA systems model. • An external flooding fragility evaluation is performed for SSCs for each POS based on the following: o a review of plant design documents, o plant configuration, and RG 1.247, Page 41 o a walkdown or the evaluation of available data and findings of investigations of the plant design and operations information for plants that have not started construction or do not have enough construction complete to allow physical walkdowns. • The uncertainties related to external flood fragility analysis are identified and characterized. The objective of an external flood plant response analysis is to develop an external flood PRA model that includes all significant flood-caused initiating events and other failures that can contribute to the plant response to and radiological consequences from external flooding events for each POS. The model for each POS is adapted from the corresponding internal events PRA model to incorporate unique flood analysis aspects that are different from the internal events PRA model. The