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:
objective of the internal fire initiating event and equipment selection is, for each POS, to identify the internal fire-induced initiating events to be evaluated in the fire PRA model and equipment to be included in the internal fire PRA model. Much of this equipment comes from the equipment included in the internal events PRA such that, if failed by an internal fire, that equipment could produce a plant initiator or affect the plant response. The plant’s fire protection program and analysis can be used to identify equipment. The critical safety functions essential to the LPSD model are reactivity control, reactor coolant chemistry control (key for NLWRs), decay heat removal control, RCS inventory/barrier control, and ex-vessel fission product control (e.g., off-gassing/fuel salt storage tanks). Internal fire- induced spurious actuations are of particular interest for initiating event and equipment selection. The selected equipment is mapped to the PAUs. The internal fire PRA model for each POS should be evaluated for the need for different or additional equipment, particularly in the case of spurious actuations. The characteristics and attributes needed to achieve the objectives of an internal fire-initiating event and equipment selection PRA analysis element are as follows: • Fire-induced initiating events to be evaluated in the internal fire PRA model are identified. • Equipment is included in the internal fire plant response model that will lead to a fire-induced plant initiator, or that is needed to respond to such an initiator (including equipment subject to fire-induced spurious actuation that affects the plant response). • The number of spurious actuations to be addressed increases according to their consequence (e.g., internal fire-induced failures leading to loss of heat sink or radionuclide transport barrier bypass require a greater number of spurious operations to be included in the fire plant response model). • Instrumentation and support