Deterioration of irradiated silicone rubber in aqueous solutions of chemicals

Weight loss characteristics of a silicone rubber were examined under a LOCA (loss of coolant accident) condition to investigate the cause of weight loss, listed such as radiation, heat and solutions of chemicals found in the LOCA state, combination of these parameters, and blending ratio of the silicone rubber. Examinations were carried out in various radiation environments (air, vacuum, oxygen over pressure), doses, solution-exposed temperatures, expose environments (water, solutions), and additives (silica, fire retarding materials). Irradiation was carried out up to 9.7 kGy/h of dose rate and solution resistant behavior was examined by an immersion technique, and the following results were obtained. As for the radiation effect on the examined silicone rubber, irradiated rubber were apt to be attacked by a reagent chemicals solution. Silicone rubbers of a practical and standard blending ratio showed similar deterioration behavior against chemical solution for air and oxygen overpressure conditions, but different for vacuum irradiation. Weight loss increased rapidly after specified radiation period, and the irradiated silicone rubber became powdered substance in this case, while irradiated silicone rubber in oxygen overpressure was deteriorated as keeping its rubber state. Deterioration in the chemical solution was found dependent on exposure dose and temperature. It was also found that fire retarding materials effected much for the deterioration in vacuum irradiation, but silica effected mainly for the deterioration in oxygen overpressure irradiation. (Takagi, S.)