Dose Rate Effects in the Aging of Nuclear Cable Insulation Subjected to Gamma Radiation

In nuclear power plants (NPPs), the aging of polymer-based electrical cable insulation must be effectively monitored to ensure safe and reliable plant operation. Gamma radiation is one of the main environmental stressors leading to degradation of cable insulation within NPPs. For a given total absorbed dose of gamma radiation, insulation damage may be dose rate dependent. To explore potential dose rate effects, the goal of this work was threefold: (1) to confirm whether a dose rate effect exists for cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR) cable insulation, (2) quantify the relationship between degradation rate and dose rate, and (3) explore the correlation between measured properties. Here, insulation damage for dose rates of 1800 Gy/h, 200 Gy/h, and 100 Gy/h using Cobalt-60 gamma irradiation was studied. A total dose of approximately 300 kGy was supplied at ambient conditions. The properties of unirradiated and irradiated samples were characterized using mass change and yellowness index. Findings indicate that dose rate effects were observed for mass change of XLPE and EPR, but not yellowness index.