Neutron irradiation to W induces defects acting as traps against hydrogen isotopes and transmutation elements such as Re and Os. To investigate synergetic effects on radiation-induced defects and Re, deuterium (D) retention in W and W–5% Re samples were examined after irradiation with 6.4MeV Fe ions at 523–1273K followed by exposure to D2 gas at 673K. The value of D retention in W–5% Re was lower than that in W by orders of magnitude after the irradiation at high temperatures (≥1073K), while no significant effects of Re addition was observed after irradiation at 523K. Irradiation with 20MeV W ions at room temperature followed by exposure to D plasma at 443–743K also resulted in small difference in D retention between W and W–5% Re samples. The results of positron lifetime measurements showed that the reduced D retention by Re observed after high temperature irradiation was due to suppression of formation of vacancy-type defects (monovacancies and vacancy clusters) by Re.
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