Effect of Radiation Deterioration on Class 1E Cable Fire

Abstract

In this study, the effect of radiation deterioration on cable fire for a type of class 1E cable for a nuclear power plant was investigated. Combustion and smoke characteristics were compared via a cone calorimeter test (ISO 5660-1), and the toxicity index of the toxic gas emitted during combustion was analyzed by following the NES 713 standard. The peak heat release rate of the irradiated cable was measured to be approximately 38 kW/m<sup>2</sup> higher than that of the non-irradiated cable. Additionally, the heat release rate of the irradiated cable temporarily increased during a certain period. This can be ascribed to the continuous pyrolysis and heat penetration as a result of the unstable formation of the char layer. The total heat release of the irradiated cable was measured to be approximately 2.2 times higher than that of the non-irradiated cable. A corresponding increase of ~2.8% in the total mass loss was observed. In the case of smoke characteristics, the irradiated cable was measured to be 2.3 times higher in the smoke parameter and 3.8 times higher in the smoke factor compared to the non-irradiated cable. For the toxicity index, only CO was detected above the critical factor in the non-irradiated cable, whereas both CO and HBr were detected above their critical factors in the irradiated cable.

Combustion Characterization according to Accelerated Deterioration Temperature of a Non-class 1E Cable

“…In Figures 6(a) and 6(b) and 6(c), the second HRR exhibited a peak value in the section after 200 s, at least once during the three repetition tests in the non-aged cable and in the 90 and 100 °C-aged cables. Regarding this characteristic, previous studies [7,19] have reported that after the first PHRR, the flame retardant added to the cable sheath and insulation after the first PHRR forms a char layer on the cable surface and blocks heat penetration. They suggest that if the flame retardant performance decreases, the formation of the char layer becomes unstabe, which weakens its intensity, and after the flame retardant performance is maintained for a certain period, the second PHRR emerges, owing to the occurrence of cracks on the surface.…”