Irradiation condition on accelerated ageing test of cable designed for nuclear power plants

Shimada, Akihiko; Kudo, Hisaaki*; Idesaki, Akira; Oshima, Takeshi; Tamura, Kiyotoshi; Seguchi, Tadao*

The lifetime evaluation of cable insulation used in nuclear power plants is very important for their safety running. In the present, the evaluation of cable lifetime is performed under the higher dose rate of radiation and elevated temperatures compared to actual conditions. In that case, we need to select the reasonable dose rate. One of the important points is the homogeneous oxidation throughout insulation polymer materials during irradiation for the equivalent oxidation with the real ageing condition. The oxidation depth of polymer material depends on the dose rate and oxygen diffusion coefficient into polymer material. Then, the dose rate could be increased if the diffusion coefficient was increased by increasing the irradiation temperature. The relations between dose rate and irradiation temperature were studied on XLPE, EPR, PVC and SiR for cable insulation. These materials are irradiated with cobalt 60 -rays at dose rates up to 1 kGy/h under elevated temperature. The irradiation effects were analyzed by tensile test, change of swelling ratio and gel fraction, SEM-EDS, and FT-IR.