SPATIAL TRITIUM TRANSPORT IN SINGLE-CRYSTAL LITHIUM ALUMINATE

Isothermal anneal tests have been performed on large single-crystal sa mples (approximately 1.5 mm diameter) of LiAlO2 in an attempt to deter mine the diffusivity of tritium in lithium aluminate. To understand th e effects-of impurities on the tritium transport, single crystals of M g-doped LiAlO2 were also studied. The crystals were sectioned after an nealing to determine the tritium concentration profiles within the cry stals. From these profiles the tritium diffusivity, D, and the desorpt ion rate constant, K, were calculated. The tritium diffusivities deter mined for the doped and undoped materials were the same within experim ental error. The measured diffusivity is given by In D(m(2)/s)= -11.8 - (1.50 x 10(4))/T. Tritium release for these samples was generally in the mixed diffusion-desorption regime, as determined from the ratio a K/D, where a is the grain radius. Our data indicate that for grain rad ii less than 100 mu m, the tritium transport will be in the desorption -controlled regime.