Effects of pre-treatments of Li2TiO3 pebbles on the release of tritium generated during short irradiations

The reduction of Li2TiO3 to Li2TiO3−x at 800 °C by He+H2 (0.1%) purge gas was studied with Li2TiO3 pebbles. The evolution of O-vacancy concentration (x(t)) allowed extrapolation to the steady-state value x(t→∞)=0.0096 which was found to be independent from the material microstructure, while the process rate and its mechanism were found to depend on the grain size, porosity and sintering temperature of the pebbles. The temperature of tritium removal from the so-treated (reduced) pebbles was found to be higher than those from the oxidized (stoichiometric) ones, the increase of x being accompanied by an increase in the population of more energetic tritium trap sites at the grain boundary interface of the material. However, this phenomenon should not be of concern under ‘normal’ breeding blanket operating conditions.