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:
s, to reflect fire-induced failure of equipment used to respond to initiating events, and to reflect the impact of fire on operator actions. Because of its dependence on the internal events model, the internal fire analysis incorporates the elements of Regulatory Positions C.1.3.1 through C.1.3.7 of this RG, as necessary. The objective of the internal fire plant boundary definition and partitioning is to establish the overall boundaries of the fire PRA and divide the area within that boundary into smaller regions (i.e., physical analysis units (PAUs)), commonly known as fire areas or compartments. The entire fire PRA is generally organized according to these PAUs. The at-power boundary definition and partition for an at- power type of POS may need to be modified for boundary elements breached during LPSD types of POSs, but not breached during at-power types of POSs. The plant boundary definition and partitioning should account for PAUs necessary for all POSs. The characteristics and attributes needed to achieve the objectives of an internal fire plant boundary definition and partitioning PRA analysis element are as follows: • The global analysis boundary should account for all plant locations relevant to the internal fire PRA for all POSs. • PAUs are identified by credited partitioning elements that can substantially confine fire damage behaviors. • The boundary definition and partition for at-power types of POSs may need to be modified for boundary elements breached during LPSD types of POSs but not breached during at-power types of POSs. RG 1.247, Page 28 • The plant boundary definition and partitioning should account for the PAUs necessary for all POSs. • The uncertainties in the internal fire PRA related to the PAUs are identified and characterized. The objective of the internal fire initiating event and equipment selection is, for each POS, to identify the internal fire-induced initiating events to be evaluated in the fire PRA model and equipment to