Synergism of Gamma-ray Irradiation and Steam Exposure on the Degradation of Silicone Rubber

Silicone rubber (SiR) is a fundamental electrical insulating material. For its use in nuclear power plants, the degradation induced by heat, gamma-ray irradiation, and steam exposure could be a concern. Therefore, their synergism on the degradation of SiR was examined experimentally. When SiR is first exposed to the steam at 200 °C, it melts and its tensile strength becomes impossible to measure. However, if the gamma-ray irradiation was given in advance, SiR is not destroyed so badly by the high-temperature steam. The reason for the above is that the formation of tight cross-linked structures via oxygens, induced by the irradiation of gamma rays, prevents the progress of hydrolysis.