Effect of irradiation dose rates on ethylene-propylene rubber for nuclear cables

Abstract

The effect of dose rates is the critical concern of irradiation testing in equipment qualification for polymeric materials used in nuclear power plants, and the rule ‘the lower dose rates, the severer degradation’ is always regarded as the truth due to the limited diffusion of oxidation. But it's obviously not economic and practical from the engineering point of view. In this paper, aiming at investigating such dose rate effects, gamma irradiation testing with multiple dose rates was performed on one domestically manufactured ethylene-propylene rubber that was intended for the nuclear cable insulations of the advanced pressurized water reactors in China. In detail, before and after testing, the mechanical, electrical and chemical properties were measured from the specimens, and their fractographs after tensile test were observed, and particularly the oxidation profiles on the whole cross sections of them were detected by the infrared microscope to quantitatively compare the degradation extent under different dose rates. Based on the results, the correlation among the dose rates, the measured properties, and the penetration depth of oxidation was clarified, the relevant degradation mechanisms were discussed, and a suitable dose rate for engineering practice was recommended.