Document: NRC Regulatory Guide
Document ID: 8e45dce1-e1e7-4415-b1dd-7e2a610e545b
Document Type: regulatory_guide
Title: Fire Protection for Nuclear Power Plants (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2023/ML20231A835.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.189
CFR Part: 
CFR Title: 

Content:
procedures will not adversely affect operating systems. 5.3 Fire Protection of Safe-Shutdown Capabilities The post-fire safe-shutdown analysis should ensure that one success path remains free of fire damage for a single fire in any single plant fire area. The NRC developed NUREG/CR-7150, “Joint Assessment of Cable Damage and Quantification of Effects from Fire (JACQUE-FIRE),” Volumes 1, 2, and 3 (Refs. 116, 117, 118), as a consensus report by technical experts on issues related to multiple spurious operations (MSOs). The report is based on the current best available evidence and represents the current state of the art. The electrical expert phenomena identification and ranking table (PIRT) panel provided the following recommendations, as documented in NUREG/CR-7150, Volume 3: a. Number of Hot Shorts for Transient Inrush Considerations—If the MSO scenario involves the potential failure of a safe-shutdown power supply resulting from a temporary overload condition caused by multiple, concurrent inrush currents (i.e., overlapping inrush transient current from multiple separate loads) due to spurious operation of multiple loads as a result of hot shorts on the DG-1359, Page 77 control cable for each load, then the MSO does not need to be considered. This recommendation is based on (1) normal transient inrush current duration, (2) the spurious operations are caused by fire damage to control cables for the loads from the power supply of concern, and the loads are otherwise operating correctly and have no potential for power cable fire damage, (3) the load sequencer, if applicable, for the associated power supply is not damaged by the fire such that it may cause multiple loads to simultaneously spuriously start, and (4) target conductors that could spuriously start or energize loads powered from the same power supply are in separate cables. In this case, the power supply availability for the fire event can be assessed by the steady-state loading (i.e., anticipated