Tritium inventory in a LiAlO 2 blanket

Abstract

Although lithium ceramic materials such as Li 2O, LiA1O 2, Li 2ZrO 3 and Li 4SiO 4 are considered as breeding materials in the blanket of a D-T fusion reactor, the release behavior of the bred tritium in these solid breeder materials has not been fully understood. Most of the results of in situ tritium release experiments are analyzed assuming that the overall release process of tritium is mainly controlled with the process of tritium diffusion in the crystal grain of a solid breeder material. However, it has been pointed out by many authors that contribution of the surface reaction cannot be ignored. Effects of diffusion of tritium in the grain, absorption of water in the bulk of grain and adsorption of water on the surface of grain together with isotope exchange reactions on the tritium inventory under the steady state condition are discussed in this study. Comparison of the estimated tritium inventory using the way of this study with the data obtained in several in situ experiments shows that good agreements are obtained when the effective diffusivity obtained from the data by Kwast et al. is used. The better agreements are obtained when existence of some water vapor is assumed in the purge gas.