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:
quently for physical analysis units. • Transient fires should be postulated for all physical analysis units regardless of administrative controls. • Appropriate justification should be provided to use nonnuclear experience to determine fire ignition frequency. Quantitative Screening • Physical analysis units that are screened out from more refined quantitative analysis are retained to establish CDF and LERF/LRF. • Typically, those fire PRA contributions to CDF and LERF/LRF that are established in the quantitative screening phase are conservatively characterized. Circuit Failure Analysis • The conditional probability of occurrence of various circuit failure modes given cable damage from a fire is based upon cable and circuit features. Post-fire Human Reliability Analysis • Operator actions and related post-initiator HFEs, conducted both within and outside of the main control room, are addressed. • The effects of fire-specific procedures are identified and incorporated into the plant response model. • Plausible and feasible recovery actions, assessed for the effects of fire, are identified and quantified. • Undesired operator actions resulting from spurious indications are addressed. • Operator actions from the internal events PRA that are retained in the fire PRA are assessed for fire effects. Fire Risk Quantification • For each fire scenario, the fire risk results are quantified by combining the fire ignition frequency, the probability of fire damage and the conditional core damage probability (and CLRP/CLERP) from the fire PRA plant response model • Total fire-induced CDF and LERF/LRF are calculated for the plant and significant contributors identified • The contribution of quantitatively screened scenarios (from the quantitative screening element) is added to yield the total risk values DG-1362, Page 24 Table 5. Summary of Technical Characteristics and Attributes of an Internal Fire PRA for the At-Power Operating Mode Element Technical