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:
d after the Megger test for power cables rated at less than 1,000 V AC. DG-1359, Appendix B, Page B-8 “Qualification Test for Circuit Integrity of Insulated Electrical Wires and Cables in Electrical Circuit Protection Systems,” is acceptable, with the following modifications: a. During the air oven test, the cables are to be energized at rated voltage. The cables are to be monitored for conductor-to-conductor faults in multiconductor cables and conductor-to-ground faults in all conductors. b. The cables being evaluated should be subjected to the Megger and Hi-Pot tests, previously recommended in Section C-3.2 of this appendix. c. The impact force test, which simulates the force of impact imposed on the raceway by the solid stream test, described in UL 1724, Appendix B, paragraph B3.16, does not need to be performed. B-3.4 Cable Thermal Exposure Threshold The following analysis is an acceptable method for evaluating cable functionality. It is based on determining whether a specific insulation material will maintain electrical integrity and operability or functionality within a raceway fire barrier system during and after an external fire exposure. To determine cable functionality, it is necessary to consider the operating cable temperatures within the fire barrier system at the onset of the fire exposure and the thermal exposure threshold (TET) temperature of the cable. For example, if the TET of a specific thermoplastic cable insulation (Brand X) is 149 degrees C (300 degrees F) and the normal operating temperature within the fire barrier system is 66 degrees C (150 degrees F), the maximum temperature rise within the fire barrier system should not exceed 83 degrees C (181 degrees F) during exposure to an external fire of a duration equal to the required fire-resistance rating of the barrier. For this example, the TET limit for Brand X cable is 83 degrees C (181 degrees F) above the cable operating temperatures within the fire barrier system at the onset of the