Lithium metatitanate, Li2TiO3, is a leading candidate for application as a
tritium breeding material in a future fusion reactor. Following transmutation of
lithium, the
tritium must escape the crystal in order to be extracted for use in the fusion plasma. The rate-limiting step to release
tritium from the Li2TiO3 pebbles is diffusion through the crystal grains. In this work, the activation barriers for
tritium diffusion have been calculated using density functional theory. The results show that
tritium can diffuse as an interstitial with a barrier of 0.52 eV. However, when a
tritium ion becomes bound to a
lithium vacancy defect, the energy required to either detrap the
tritium from the vacancy or for the cluster to diffuse increases to >1 eV. Overall, these results suggest that the introduction of
lithium vacancies due to Li
burn-up may lead to an increase in
tritium retention in the pebbles.