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:
(including electrical circuits that could prevent operation or cause maloperation caused by hot shorts, open circuits, or shorts to ground) of redundant success paths necessary to achieve and maintain hot-shutdown conditions are located within the same fire area outside the primary DG-1359, Page 79 containment, the licensee should provide, for currently operating reactor plants, one of the following means of ensuring that one of the success paths (of SSCs for hot shutdown) is free of fire damage. (Regulatory Position 8.2 of this guide provides the protection requirements for redundant post-fire safe-shutdown success paths in new reactor plants.) a. Separation of redundant post-fire safe-shutdown success paths by a fire barrier having a 3-hour rating should be achieved. Structural steel forming part of or supporting the fire barrier should be protected to provide fire resistance equivalent to that of the barrier. b. Separation of redundant post-fire safe-shutdown success paths by a horizontal distance of more than 6.1 m (20 ft) with no intervening combustible or fire hazards should be achieved. In addition, fire detectors and an automatic fire suppression system should be installed in the fire area. c. Insulation of electrical cables, including those with fire-resistive coatings, should be considered as intervening combustibles in other than negligible quantities (i.e., isolated cable runs), as determined by engineering and fire hazards analysis. Cables in conduits are not considered intervening combustibles. d. Enclosure of one redundant post-fire safe-shutdown success path in a fire barrier having a 1-hour rating should be achieved. In addition, fire detectors and an automatic fire suppression system should be installed in the fire area. To meet the provisions of items b and c above, the installation of fire suppression and detection equipment in a fire area should be sufficient to protect against the hazards of the area. In this regard, detection and suppression