Modeling of surface reaction in tritium release from lithium ceramics and its comparison with transient experiments

Among the various tritium transport processes in lithium ceramics, the importance and the detailed mechanism of surface reactions still remains to be elucidated. A dynamic adsorption and desorption model for tritium desorption from lithium ceramics, especially Li2O was constructed. This model was improved in order to simulate tritium release behavior during temperature and sweep-gas composition changes. The surface heterogeneity of HTO release was also included by introducing multiple activation energies for desorption, which are assumed to be related to the number of oxygen vacancies, denoted OH- and OT-, on the surface. The kinetic coefficients required for calculation were also improved by using recent experimental and/or reported data.Calculation results for sweep-gas composition and temperature changes were compared with BEATRIX-II experiments. The tritium release transient behavior and the chemical form of the released tritium were discussed. (orig.)