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:
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 for horizontal and vertical cable trays should be qualified by tests.3 The penetration qualification tests should use the time-temperature exposure curve specified by ASTM E-119, "Fire Test of Building Construction and Materials." Openings inside conduit larger than 4 inches in diameter should be sealed at the fire barrier penetration; these seals should be qualified by tests as described above. Openings inside conduit 4 inches or less in diameter should be sealed at the fire barrier and should be qualified by tests as described above unless the conduit extends at least 5 feet on each side of the fire barrier and is sealed either at both ends or at the fire barrier with noncombustible material to prevent the passage of smoke and hot gases. Fire barrier penetrations that must maintain environmental isolation or pressure differentials should be qualified by test to maintain the barrier integrity under the conditions specified above. (4) Fire stops should be installed every 20 feet along horizontal cable routings in areas that are not protected by automatic water systems. Vertical cable routings. should have fire stops installed at each floor/ceiling level. Between levels or in vertical cable chases, fire stops should be installed at the midheight if the vertical run is 20 feet or more but less than 30 feet or at 15-foot intervals in vertical runs of 30 feet or more unless such vertical cable routings are protected by automatic water systems directed on the cable trays. Individual fire stop designs should prevent the propagation of a fire for a minimum period of thirty minutes when tested for the largest number of cable routings and maximuia cable density. 2 Trays exceeding 24 inches should be ccunted as two trays; trays exceeding 48 inches should be counted as three