Neutron irradiation scoping study of twenty-five copper-base materials

Abstract

A scoping irradiation test was carried out to help define the performance of copper-base materials in potential fusion applications. Twenty-five different copper materials including oxide dispersion-stabilized and precipitation-hardened powder metallurgy alloys, as well as pure copper and solid solution-strengthened ingot alloys, were neutron irradiated to 13.5 dpa at 400°C in the Experimental Breeder Reactor II (EBR-II) fast reactor. Volumetric swelling and electrical conductivity data were measured for all irradiated materials, and four selected materials were characterized for mechanical property changes using a miniaturized disk bend test. A number of these copper alloys, especially those prepared by powder metallurgy techniques, showed low swelling (less than 0.3%), small changes in conductivity (less than ± 5%), and relatively small changes in yield strength with good post-irradiation ductility. Preliminary electron microscopy results show microstructural changes that are consistent with the results of the macroscopic studies. The pure copper materials showed significant changes in conductivity and high levels of swelling as a result of the neutron exposure. It is apparent that a variety of copper alloys can survive fast neutron exposures to at least 13.5 dpa at 400°C without unacceptable changes in density, conductivity, or yield strength. Further irradiation testing to much higher doses and experimental investigation of the effect of transmutation product gases are needed to fully define the response of available copper alloys to fusion reactor environments.