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:
tions). • 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. • Inapplicable aspects of the internal events PRA model are bypassed for a particular POS. • The uncertainties in the internal fire PRA related to the internal plant response model are identified and characterized. The objective of the internal fire scenario selection and analysis is to define and analyze fire event scenarios that represent the plant fire risk associated with each PAU. Internal fire scenarios are defined in terms of ignition sources, fire growth and propagation, fire detection, fire suppression, and cables and equipment (“targets”) damaged by the internal fire. Main control room internal fire scenarios, including control room abandonment, are analyzed explicitly. Multicompartment fire propagation scenarios, including scenarios from all screened PAUs, are also assessed and screened as appropriate. The ability to develop internal fire scenarios in the fire PRA is limited by the information known about the plant (i.e., the lack of as-built details) prior to construction. Particularly for LPSD types of POSs, data is important in establishing the availability of fire protection features and systems, including the status of RG 1.247, Page 30 those fire protection features and systems during the particular POS and the plant conditions under which they are available. Also, the nature and amount of transient fuel sources introduced in the plant during the POS may differ between at-power and LPSD types of POSs. All POSs should be evaluated for differences in the internal fire scenario selection and analysis PRA analysis element. The characteristics and attributes needed to achieve the objectives of an internal fire scenario selection and analysis PRA analysis element are as follows: • Internal fire scenarios are defined in terms of ignition sources, fire