Effect of low temperature reactor irradiation on organic insulators in superconducting magnets, (3)

Organic insulators, such as polyimide, epoxy resins and fiber reinforced epoxies (FRP), are irradiated in the fission reactor at about 5K and their mechanical properties are measured in liquid helium without warm-up. At the very low temperature, the materials are completely brittle and the serration in the stress-strain curves takes place on polyimide, epoxy resins and CFRP. After irradiation of the absorbed dose of 1.1 x 109 rad at about 5K, the breaking stress of epoxy resins reduces by 30 -- 40% and FRP and polyimide exhibit a little decrease in the mechanical strength. FRP and polyimide have good radiation resistance on the mechanical behavior after dose of --1 x 109 rad as compared with other selected organic materials. (author)