Retention of Hydrogen Isotopes in Neutron Irradiated Tungsten

To investigate the effects of neutron irradiation on hydrogen isotope retention in tungsten, disk-type specimens of pure tungsten were irradiated in the High Flux Isotope Reactor in Oak Ridge National Laboratory followed by exposure to high flux deuterium (D) plasma in Idaho National Laboratory. The results obtained for low dose n-irradiated specimens (0.025dpa for tungsten) are reviewed in this paper. Irradiation at coolant temperature of the reactor (around 50°C) resulted in the formation of strong trapping sites for D atoms. The concentrations of D in nirradiated specimens were ranging from 0.1 to 0.4mol% after exposure to D plasma at 200 and 500°C and significantly higher than those in nonirradiated specimens because of D-trapping by radiation defects. Deep penetration of D up to a depth of 50­100µm was observed at 500°C. Release of D in subsequent thermal desorption measurements continued up to 900°C. These results were compared with the behaviour of D in ion-irradiated tungsten, and distinctive features of n-irradiation were discussed. [doi:10.2320/matertrans.MG201204]