Tritium release from lithium silicate pebbles produced from lithium hydroxide

Out-of-pile tritium release experiments were performed using slightly overstoichiometric lithium orthosilicate pebbles irradiated in a research reactor. In the experiments, various sweep gases such as pure nitrogen gas, hydrogen/nitrogen gas and water vapor/nitrogen gas are used to investigate the effect of difference in sweep gas composition on tritium release form the breeder material. The experimental results indicate that almost all tritium was released as tritiated water vapor regardless of difference in gas composition of the sweep gas. Most of the chemical form of tritium released was tritiated water vapor even when the hydrogen/nitrogen gas was used for the sweep gas. It was also found that a considerably smaller amount of tritium was released when a pure nitrogen gas was used as the sweep gas. Comparison of the experimental results reveals that the tritium release rate is substantially enhanced if the sweep gas contains water vapor.