ADVANCED UNDERSTANDING OF THE TRITIUM RECOVERY PROCESS FROM THE CERAMIC BREEDER BLANKET

The key to successful operation of a tritium breeder blanket is to und erstand the tritium transport and release characteristics and the role that hydrogen plays in this process. Indications are that grain size (surface-to-volume ratio) largely determine whether tritium release is limited by diffusion or desorption. That is, the larger the grain siz e the higher the probability that bulk diffusion will determine the re lease rate. For smaller grain size, the actions taking place on the gr ain surface become extremely important especially as regards the role that hydrogen plays in the overall process. Experimental studies have indicated that the presence of 0.1% H-2 in the helium purge gas enhanc es the release of tritium from the lithium ceramic. The tritium releas ed has been found in the form of both HT and HTO. The ab initio calcul ations on the dissociative hydrogen chemisorption on lithium oxide sur faces provide one component of the quantitative basis for an understan ding of the role of hydrogen in affecting the release of tritium from lithium ceramic breeders. These calculations suggest heterolytic adsor ption of hydrogen onto the ceramic surface. (C) 1997 Elsevier Science B.V.