Low temperature irradiation effects on mechanical properties of epoxy used in superconducting magnets

Abstract

Superconducting magnets for fusion devices are greatly influenced by the radiation environment and the principal radiation-induced troubles arise from changes in the mechanical fracture behaviour of organic materials used as insulating and/or potting materials. Small compression test specimens of epoxy resin were tested after gamma and pile irradiation at low temperatures. Three kinds of mechanical properties, ie a — breaking stress, b — breaking strain and c — elastic moduli were investigated. A statistical analysis of the data from a large number of small specimens revealedt the following: 1. the different effects of gamma and neutron irradiation on the fracture behaviour were observed. This fact suggests that a simulation study by gamma irradiation is not valid for neutron irradiation. 2. in the case of reactor irradiation overall softening was induced accompanied by local hardening and embrittlement. A qualtitative explanation of the above results is presented and their relationship to the performance of the magnets is given.