Effects of hydrogen and helium produced by transmutation reactions on void formation in copper isotopic alloys irradiated with neutrons

Three kinds of copper isotopic alloys 63Cu, 63+65Cu (50 at.% 63Cu + 50 at.% 65Cu) and 65Cu were used to investigate the intrinsic effects and the synergetic effects of transmutation productions, hydrogen and helium, on void swelling. Helium is produced from 63Cu by (n, α) reaction and hydrogen by 63Cu and 65Cu by (n, p) reaction under the fission neutron irradiation. It was found that both hydrogen and helium enhanced the void swelling of copper. Although production of hydrogen was higher than that of helium in the present work, the effect of hydrogen was only prominent at 646 K but not at 683 K. The effect of helium on void swelling appeared at 683 K.