Exploring the Effect of Radiation on the Crystal Structure and Dielectric Response of XLPE

Cables in nuclear power plant (NPP) may be affected by radiation rays during operation, which may lead to insulation failure. Therefore, the changes of cross-linked polyethylene (XLPE) crystal structure and its degradation process under different radiation doses were studied in this paper. First, the cables used in NPPs were irradiated with different doses of
$\gamma$
-rays, and then the XLPE crystal structure, mechanical properties were obtained by X-ray diffraction test, differential scanning calorimetry test and tensile test. Finally, the interfacial polarization process between the crystal region and the amorphous region after irradiation was analyzed from polarization and depolarization currents. The results showed that with the increase of radiation dose, the crystallinity of XLPE dropped no more than 20% and the crystal size and crystal plane spacing increase about 25%, which indicates that the XLPE crystal region is not completely destroyed by irradiation, but becomes looser. Meanwhile, the elongation at break of 720 kGy sample was less than 50% of the initial value. Irradiation will weaken the connection between the lamellar and make it easier to slip, resulting in a rapid decline in mechanical properties; the interfacial polarization between the crystal region and the amorphous region will become more remarkable due to oxidation and chain scission.