Effects of Heat and Radiation on Flame-Retardant and Non-Flame-Retardant XLPE Cables

The leakage current was measured by applying the current integration method for cables insulated with flame-retardant (FR) cross-linked polyethylene (XLPE) and non-FR-XLPE, used as safety-related cables in nuclear power plants in Japan. As a result, it has been clarified that FR-XLPE is much more vulnerable to deterioration due to heating and radiation than XLPE. Namely, after heating and gamma-ray irradiation, distinct leakage current flows in the FR-XLPE cables even at a low electric field. However, the insulation resistances of the cable insulator calculated from the leakage currents flowing through FR-XLPE cables variously treated are several orders of magnitude higher than the value required for electrical insulation of circuits. This means there are no concerns about the insulation characteristics of the cables insulated with both non-FR-XLPE and FR-XLPE.