Understanding the Fire Hazards of Grouped Electrical Cables | NIST

Nuclear power plants typically contain hundreds of kilometers of electrical cables. The in situ fire fuel load is dominated by cable insulating materials in most areas of a plant. The cables are found in both routing raceways and electrical cabinets. In a postulated fire scenario, they can be an ignition source, an intervening combustible, and/or a device that can potentially lose functionality. The cables are made up of a variety of thermoplastic (TP) and thermoset (TS) materials. Thermoplastic materials tend to melt and drip when burned, whereas thermosets tend to form a char layer. Electrical cables have been responsible for, or contributed to, a number of fires in commercial nuclear plants over the years. In 1975, a serious fire involving electrical cables occurred at the Browns Ferry Nuclear Power Plant operated by the Tennessee Valley Authority [1]. The fire caused damage to more than 1,600 cables resulting in loss of all Unit 1 emergency core cooling system equipment. The damage was extensive because of the flammability of the cables, including ease of ignition, and flame spreading.