Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
es and those actions retained from the internal events PRA. The latter HFEs are modified to account for internal fire effects. The characteristics and attributes needed to achieve the objectives of an internal fire HRA PRA analysis element are as follows: • Operator actions and related post-initiator HFEs, conducted both within and outside of the main control room, are addressed. RG 1.247, Page 32 • The effects of internal fire-specific procedures are identified and incorporated into the plant response model. • Plausible and feasible recovery actions, assessed for the effects of internal 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 internal fire PRA for a particular POS are assessed for fire effects. • The uncertainties related to the internal fire HRA PRA analysis element are identified and characterized. The objective of the internal fire event sequence quantification is to calculate the frequency of the internal fire-induced event sequence (i.e., the fire ignition frequency and the probability of fire damage). This factor is then integrated with the conditional probability of the event sequence from the internal fire PRA plant response model for the appropriate POS to quantify the risk. In the internal fire event sequence quantification PRA analysis element, dependencies are addressed, risk-significant contributors to event sequences are identified, the uncertainty in PRA results is characterized, and the event sequence quantification results are reviewed for correctness, completeness, and consistency. The characteristics and attributes needed to achieve the objectives of an internal fire sequence quantification PRA analysis element are as follows: • For each internal fire scenario, the internal fire risk results are quantified by combining the internal fire ignition frequency, the probability of fire