Release kinetics of tritium generated in lithium-enriched Li2+xTiO3 by thermal neutron irradiation

Abstract

Tritium release kinetics for Li2+xTiO3, the lithium-enriched Li2TiO3, was investigated by isochronal and isothermal annealing experiments. Tritium release by isochronal annealing showed that the dominant release stage was found at around 600K. An additional release stage at lower temperature side was appeared with increasing excess lithium, which was attributed to the release of tritium trapped in Li4TiO4 structure. The dominant release stage was considered to a release of tritium trapped by irradiation defects. Isothermal annealing experiments indicated that tritium releases were controlled by diffusion process. The diffusion coefficient of Li2.0TiO3 was one order of magnitude as large as those of Li2.2TiO3 and Li2.4TiO3, although their activation energies were almost the same. These results showed that rate-determining step was the diffusion process of tritium in Li2TiO3 structure for Li2+xTiO3 and excess lithium would make diffusion coefficient smaller. Simulation of tritium-TDS spectra for Li2.0TiO3 has clarified that the TDS spectrum forLi2.0TiO3 can be demonstrated by using Arrhenius diffusion parameters obtained by isothermal annealing experiment in the present study.