Document: NRC Regulatory Guide
Document ID: 80776ca5-a83d-4667-9a94-0bffa1befa91
Document Type: regulatory_guide
Title: Fire Protection Guidelines for Nuclear Power Plants (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1221/ML12216A013.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.120
CFR Part: 
CFR Title: 

Content:
lowing conditions are met: # (a) The number of equivalent2 standard 24-inch-wide cable trays (both safety- related and non-safety-related) in a given fire area is six or less; (b) The cabling does not provide instrumentation, control, or power to systems required to achieve and maintain cold shutdown; and (c) Smoke detectors are provided in the area of these cable-routings, and con- tinuous line-type heat detectors are provided in the cable trays. Safety-related cable trays that are not accessible for manual fighting should be protected by a zoned automatic water system with open-head deluge or open directional spray nozzles arranged so that adequate water coverage is provided for each cable tray. Such cable trays should also be protected from the effects of a potential exposure fire by providing auto- matic water suppression in the area where such a fire could occur. In such plant areas as primary and secondary containment or other areas where it may not be possible because of other overriding design features necessary for reasons of nuclear safety to separate redundant safety-related cable systems by 3-hour-rated fire barriers, cable trays should be protected by an automatic water system with open-head deluge or open directional spray nozzles arranged so that adequate water coverage is provided for each cable tray. Such cable trays should also be protected from the effects of a potential exposure fire by providing automatic water suppression in the area where such a fire could occur. The capability to achieve and maintain safe shutdown considering the effects of a fire involving fixed and potential transieni combustibles should be evaluated with and without actuation of the automatic suppression system and should be justified on a suitably defined basis. (3) Cable and cable tray penetration of fire barriers (vertical and horizontal) should be sealed to give protection at least equivalent to that required of the fire barrier. The design of fire barrier penetrations