Response Bias of Electrical Cable Coatings at FIRE Conditions (REBECCA-FIRE)
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
This report presents the results of a series of cable fire-retardant coating tests sponsored by the US Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research and performed at Sandia National Laboratories in conjunction with the National Institute of Standards and Technology (NIST). The goal of the tests was to assess the effects of three commercially available fire-retardant cable coating materials on cable thermal and electrical response behavior under fire-exposure conditions. The specific test objectives were to assess, under severe radiant heating conditions, how the coating materials impacted (1) cable thermal response and (2) electrical integrity behavior. The tests were not explicitly designed to assess the impact of the coatings on cable flammability, although some insights relative to the burning behavior of the coating materials themselves and cable ignition times were gained. NIST is currently investigating these attributes under the Cable Heat Release, Ignition, and Spread in Tray Installations During Fire (CHRISTIEFIRE) program (NUREG/CR-7010). The cables used in construction of the test articles were all seven-conductor 12AWG (American wire gage) control or power type copper conductor electrical cables. Two cable insulation types were represented, a polyethylene thermoplastic material and a cross-linked polyethylene thermoset material. Both cable types used have been tested extensively in recent NRC-sponsored experimental programs involving both circuit failure modes and effects testing and fire growth testing. The test articles included uncoated cables and cables coated with one of three fire-retardant coating materials: Carboline Intumastic 285, Flamemastic F-77, and Vimasco 3i. Test configurations included single lengths of cables, bundles of seven cables, and bundles of ten cables. The tests show that, under certain conditions, the fire-retardant coatings provide a substantial benefit relative to delays in cable heating, ignition and electrical failure times. However, as has been seen in prior test programs, the performance varied substantially among the coating products. The current tests also show that the benefit gained by the coatings was heavily dependent on the thermal mass of the coated cable system. Low thermal mass systems, such as the single lengths of coated cable, saw essentially no net benefit from application of the coatings. Intermediate mass systems, represented by the seven-cable bundles, saw some benefit from application of the coatings, but the benefit was inconsistent, and some cables in the bundles saw essentially no delay in thermal response or time to failure. For the larger thermal mass systems, represented by the ten-cable bundles, the benefit of the coatings was both more pronounced and more consistent with all coatings providing a measurable benefit.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USNRC; USDOE National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- AC04-94AL85000; NA0003525
- OSTI ID:
- 1493360
- Report Number(s):
- SAND-2019-0920R; 671911
- Country of Publication:
- United States
- Language:
- English
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