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. Sheets of SiR were irradiated with gamma rays at either high dose rate at room temperature or low dose rate at 100 ℃ and exposed to steam with no oxygen at either 171 or 200 ℃ for seven days. They were then subjected to spectroscopic and mechanical tests. When SiR is first exposed to the steam at 200 ℃, it melts and no further experiments are possible to continue. 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. The gamma-ray irradiation can alleviate the hydrolytic degradation of SiR.

aging,mitigation,gamma rays