Effects of helium and ambient water vapor on tritium release from Li 2 TiO 3

Abstract The effects of hydrogen isotopes in tritium recovery gas and the presence of helium on the tritium release behaviors were investigated for lithium meta-titanate (Li 2 TiO 3 ) to develop a tritium migration model. The tritium trapping sites as oxygen vacancies and oxygen atoms with dangling bonds were formed by energetic tritium ion implantation. Isotope exchange processes with water vapor in purge gas enhanced the recovery of tritium adsorbed on the surface of Li 2 TiO 3 and trapped in oxygen vacancies. Replacement of tritium as hydroxyl groups with hydrogen isotopes from purge gas was hardly occurred due to the higher trapping energy of tritium as hydroxyl groups. Helium implantation would induce the formation of helium bubbles, which would occupy irradiation damages, contributing to the decrease in the densities of trapping site for tritium. Consequently, the addition of hydrogen isotopes in the tritium recovery gas and the presence of helium in tritium breeding materials can contribute to the efficient tritium recovery for tritium breeding materials.