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

Among tritium migration steps from lithium ceramics, the mechanism of surface reaction or desorption process remains to be elucidated. This has been studied by combining in-situ tritium release experiments, off-pile experiments and modeling efforts. The authors constructed DAD (Dynamic Adsorption and Desorption) model for tritium desorption from lithium ceramics specially Li2O. This model assumes that the surface is covered with hydroxyl ions, oxygen ions and voids (oxygen vacancies). The fractions of these species were determined from the partial pressures of H2 and H2O in the sweep gas by adsorption and desorption reactions of H2O and H2. Tritium is released by three processes: as HTO by recombination of -OH and -OT on the surface, as HT by recombination of -OH and -OT at low oxygen potential or when these surface groups are surrounded by open-quotes activeclose quotes oxygen vacancies, and as HT by exchange reaction of surface -OT with H2 in the gaseous phase