Radiation effects on the mechanical properties of insulators for fusion magnets

Glass fiber reinforced plastics (GFRPs) are usually employed as insulating materials for the superconducting coils of large fusion magnets, e.g. of the International Thermo-nuclear Experimental Reactor (ITER). Both the radiation spectrum and the stresses at the magnet location significantly influence the mechanical behavior of the magnet insulation and, therefore, impose high demands on the material performance. During the last decades, advanced epoxy based GFRPs with improved mechanical properties and radiation hardness were introduced into fusion technology. More recently, cyanate ester (CE) matrix systems have become of special interest. In this paper, various magnet insulation systems containing boron-free glass fiber reinforcements in commercial and new epoxies as well as in pure CE and CE/epoxy/polyimide/bismaleimide blended matrix systems, are presented. All systems were irradiated in a fission reactor at ambient temperature (∼340 K) to a fast neutron fluence of 1 × 1022 m−2 (E > 0.1 MeV) and beyond. The mechanical properties were assessed at 77 K in tension as well as in interlaminar shear prior to and after irradiation under static and dynamic conditions.