Tritium trapping states induced by lithium-depletion in Li2TiO3

Identifications of tritium trapping states in neutron-irradiated Li1.8TiO2.9 (lithium-depleted Li2TiO3) were carried out by the out-of-pile tritium release behavior. Tritium release behaviors for neutron-irradiated Li2TiO3 and tritium gas-exposed TiO2 were also measured for comparison. Among the tritium release spectra for these samples, three tritium release peaks were appeared. By the kinetic analyses of tritium release behaviors, the Arrhenius parameters for three peaks were evaluated. Especially for Li1.8TiO2.9, there were two tritium release peaks, and the peak in lower temperature region was assigned to the tritium release controlled by the diffusion process in Li2TiO3 structure. The other tritium release peak, which was hardly appeared for Li2TiO3, was assigned to the release of tritium trapped as hydroxyl groups in Li1.8TiO2.9, indicating that lithium-depletion would result in the formation of hydroxyl groups in Li2TiO3. Lithium vacancies existed in Li2TiO3 crystal structure would promote the tritium trapping as hydroxyl groups due to the decreased charge repulsion between lithium ions and tritium ion, resulting in the difficulty of recovering tritium from Li2TiO3 effectively.