Hydrogen isotope exchange in tungsten during heating in hydrogen isotope gas atmosphere

In the present study, successive exposure to tritium gas and deuterium gas was performed at elevated temperatures for tungsten samples with irradiation defects created by helium ion irradiation to investigate the effects of hydrogen isotope exchange on tritium removal. It was found that, under the present heating conditions, heating treatment in deuterium gas was more effective for tritium removal than heating in a vacuum. In addition, heating in deuterium gas was effective to remove tritium retained in a deep region of sample comparing to the case of heating in a vacuum. The enhanced tritium release was explained by enhanced tritium detrapping due to trap occupation by deuterium and/or the increase in probability of surface recombination under deuterium gas exposure.