MODELING OF THE SURFACE-REACTION OF TRITIUM RELEASE FROM LITHIUM CERAMICS

From the results of in-situ tritium release experiments(TTTEx), it was clarified that tritium release from the Li2O surface is affected by b oth the swamping effects with H-2 and H2O, and the oxygen potential ne ar the surface. A model named DAD was constructed which includes these two effects by considering the dependencies of surface coverages of O H-, O2- and empty sites (oxygen vacancies on O2-) lattice sites and th e interstitial sites not occupied by OH- or O2- on the partial pressur es of H-2 and H2O in the sweep gas. In this model, desorption of surfa ce tritium as HT is considered by the recombination with surface OH- w hen they are surrounded with active oxygen vacancies, and by the excha nge reaction with H-2 in the gas phase. The result of this model calcu lation agreed fairly well with the experimental results.