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:
n the internal fire PRA related to cable selection are identified and characterized. The objective of the internal fire qualitative screening is to eliminate certain PAUs defined in the plant boundary definition and partitioning element that can be shown to be unimportant to fire risk for a POS. These screening criteria should be general qualitative criteria. Those PAUs screened out in the internal fire qualitative screening PRA analysis element play no role in the more detailed quantitative assessment. The characteristics and attributes needed to achieve the objectives of an internal fire qualitative screening PRA analysis element are as follows: • Qualitatively screened out PAUs represent negligible contributions to risk and are considered no further for a POS. • The uncertainties in the internal fire PRA associated with qualitative screening are identified and characterized. The objective of the internal fire plant response model is to develop a logic model that represents the plant response following an internal fire. This model is based on the internal events PRA model for a POS. The internal events PRA model for a POS is modified to account for fire effects, including modifications due to SSC failures that specifically result from fire and consideration of fire- specific procedures. The latter are processed through the internal fire human reliability PRA analysis element. The characteristics and attributes needed to achieve the objectives of an internal fire plant response model PRA analysis element are as follows: • Based on the internal events PRA, the logic model for a POS is adjusted to add new internal fire-induced initiating events and modified or new event sequences, operator actions, and accident progressions (in particular those from spurious actuations). • Issues relevant to the internal fire PRA (e.g., those relevant findings from a peer review of the internal events PRA) are resolved and incorporated into the fire plant response model. •