Interaction of tritium gas with Li2O crystals and dissolution processes

Interactions of T2, HT and H2 with crystalline Li2O powders as well as with single crystals were studied with emphasis on the dissolution processes. The solubility was measured with an equilibrium-quenching method at pressures from 0.02 to 70 kPa in the temperature range between 473 and 973 K. Although the amount of tritium dissolved in Li2O crystals increased as the square root of the equilibrium pressure, a discontinuity was observed at a pressure around 1-5 kPa. The heat of dissolution was 16.5±2.0 kJ/mol at 0.3 kPa and 24.3±0.9 kJ/mol at 67 kPa. The result suggested that chemical reactions, such as Li2O(s)+H2(g)→LiOH(s)+LiH(s), are involved in the dissolution process at pressures above 5 kPa. On the other hand, a dissociative adsorption step was suggested to play a dominant role in the course of dissolution in the low pressure range. (orig.)