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:
cenarios. 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 augmented with plant- specific experience, are used where available to establish the fire ignition frequencies. Other sources are generally used only for cases when the U.S. nuclear power industry does not provide the representative frequency. Quantitative screening involves eliminating physical analysis units from further quantitative analysis based on their quantitative contribution to fire risk. Quantitative screening criteria are established in terms of fire-induced CDF and LERF/LRF. This element is not required, although it is used in most applications. Note that, unlike the physical analysis units screened during qualitative screening, the CDF and LERF/LRF contributions of each of these quantitatively screened units are retained and reported as a part of the total plant fire risk in the fire risk quantification element. All physical analysis units are DG-1362, Page 22 reconsidered as a part of the multicompartment fire scenario analysis, regardless of the quantitative screening results. Circuit failure analysis treats the impact of fire-induced circuit failures upon the plant response. In particular, spurious actuations from hot shorts (inter-cable and intra-cable) are analyzed. The conditional probability of the particular circuit failure is identified and assigned. Post-fire human reliability analysis is conducted to identify operator actions and related HFEs, both within and outside the main control room, for inclusion in the plant response model. This element also includes quantification of HEPs for the modeled actions. Modeled operator actions include those introduced into the plant response model resulting strictly from fire-related emergency procedures and those actions retained from the internal events PRA. The latter HFEs are modified to account for fire