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:
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 equipment selection technical element. The selected cables are mapped to the physical analysis units. Qualitative screening is an optional element that may be used to eliminate certain physical analysis units defined in the plant boundary definition and partitioning element that can be shown to be unimportant to fire risk. General, qualitative criteria are typically applied. Those physical analysis units screened out in this technical element play no role in the more detailed quantitative assessment. Fire PRA plant response model develops a logic model that represents the plant response following a fire. This model is based upon the internal events PRA model which is modified to account for fire effects. These modifications include system, structure, and component failures that specifically result from fire and consider of fire-specific procedures. The latter are processed through the human reliability analysis technical element. Fire scenario selection and analysis defines and analyzes fire event scenarios that capture the plant fire risk associated with each physical analysis unit. 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 fire. Main control room fire scenarios, including control room abandonment, are analyzed explicitly. Multicompartment fire propagation scenarios, including scenarios from all screened physical analysis units, are also assessed. Fire ignition frequencies are estimated for the ignition sources postulated for the fire scenarios. Ignition sources consist of in situ sources, such as electrical cabinets or batteries, and other sources such as transient fires. U.S. nuclear power industry fire event frequencies, possibly