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:
ponse). • The number of spurious actuations to be addressed increases according to the significance of the consequence (e.g., interfacing systems LOCA). • Instrumentation and support equipment are included. Cable Selection • Cables that are required to support the operation of fire PRA equipment (defined in the equipment selection element) are identified and located. Qualitative Screening (Optional Element) • Screened out physical analysis units represent negligible contributions to risk and are considered no further. Fire PRA Plant Response Model • Based upon the internal events PRA, the logic model is adjusted to add new fire-induced initiating events and modified or new accident sequences, operator actions, and accident progressions (in particular those from spurious actuations). • Inapplicable aspects of the internal events PRA model are bypassed. DG-1362, Page 23 Table 5. Summary of Technical Characteristics and Attributes of an Internal Fire PRA for the At-Power Operating Mode Element Technical Characteristics and Attributes Fire Scenario Selection and Analysis • Fire scenarios are defined in terms of ignition sources, fire growth and propagation, fire detection, fire suppression, and cables and equipment (“targets”) damaged by fire. • The effectiveness of various fire protection features and systems is assessed (e.g., fixed suppression systems). • Appropriate fire modeling tools are applied. • The technical basis is established for statistical and empirical models in the context of the fire scenarios (e.g., fire brigade response). • Scenarios involving the fire-induced failure of structural steel are identified and assessed (at least qualitatively). Fire Ignition Frequencies • Frequencies are established for ignition sources and consequently for physical analysis units. • Transient fires should be postulated for all physical analysis units regardless of administrative controls. • Appropriate justification should be provided to