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:
successful test. The staff considers monitoring the cable temperature as the primary means of determining cable tray or raceway fire barrier performance to be nonconservative. Therefore, the staff has incorporated the provision for a post-fire visual inspection of cables that are installed in fire barrier test specimens. As discussed above, temperatures monitored on the exterior surface of the raceway provide a more representative indication of fire barrier performance. Fire endurance tests of raceway fire barrier systems may be performed with or without cables in the raceway. Excluding cables from the test specimen eliminates bias in the test results created by the thermal mass of the cables and is the method preferred by the U.S. Nuclear Regulatory Commission (NRC). Without the thermal mass of the cables, the internal temperature conditions measured by the test specimen thermocouples during the fire exposure will provide a more accurate determination of fire barrier thermal performance. The following sections provide guidance for both approaches. B-1.1 Thermocouple Placement—Test Specimens Containing Cables The following are acceptable placements of thermocouples for determining the thermal performance of raceway or cable tray fire barrier systems that contain cables during fire exposure: DG-1359, Appendix B, Page B-3 a. Conduits: The temperature rise on the unexposed surface of a fire barrier system installed on a conduit should be measured by placing the thermocouples every 152 millimeters (mm) (6 inches (in.)) on the exterior conduit surface under the fire barrier material. For the thermocouples installed on conduits, cable tray side rails, and bare copper conductors, a +13-mm (+0.5-in.) installation tolerance is acceptable. The thermocouples should be attached to the exterior conduit surface located opposite the test deck and closest to the furnace fire source. Thermocouples should also be placed immediately adjacent to all structural members, supports, and