Document: NRC Regulatory Guide
Document ID: 22ccfd5e-c5d8-4615-a02c-32369aa9f533
Document Type: regulatory_guide
Title: Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1930/ML19308B636.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.200
CFR Part: 
CFR Title: 

Content:
ts for an internal fire, at-power PRA. The objective for each technical element is briefly described and the characteristics and attributes needed to achieve the objective are provided in Table 5. The technical elements for an internal fire, at-power PRA are: • plant boundary definition and partitioning • equipment selection • cable selection • qualitative screening • fire PRA plant response model • fire scenario selection and analysis • fire ignition frequencies • quantitative screening • circuit failure • fire risk quantification • fire/seismic interactions DG-1362, Page 21 PRA models of internal fire are based on an existing up-to-date internal events, at-power PRA model, which is modified to reflect fire-induced failure of equipment contributing to or causing initiating events, fire-induced failure of equipment used to respond to initiating events, and the impact of fire on operator actions. Because of its dependence on the internal events model, the internal fire PRA incorporates the elements of regulatory positions C.1.2.1 and C.1.2.2 of this guide as necessary. Plant boundary definition and partitioning establish the overall boundaries of the fire PRA and divides the area within that boundary into smaller regions (i.e., physical analysis units), commonly known as fire areas or compartments. The entire fire PRA is generally organized according to these physical analysis units. Equipment selection identifies the equipment to be included in the fire PRA model. This equipment is selected from the equipment included in the internal events PRA and in the plant’s fire protection program and analysis (i.e., the postfire safe-shutdown analysis) that, if failed by a fire, could produce a plant initiator or affect the plant response. Fire-induced spurious actuations are of particular interest. The selected equipment is mapped to the physical analysis units. Cable selection identifies those cables associated with the equipment identified in the