Enhancement of tritium release from ceramic breeders with impregnated catalytic additives

In most current designs of D-T fusion reactor breeding blankets employing Li-based ceramic as breeder materials, the use of a helium sweep gas containing 0.1% of hydrogen is contemplated to extract tritium via isotopic exchange reactions. However, at lower temperatures, the release process of tritium from the breeders is known to be rather slow. For this reason, there is still a need to develop techniques that promote the release of bred tritium. In order to improve recovery of tritium from blankets over a wide range of temperature, the effect of catalytically active metal additives on the heterogeneous isotope exchange reactions at the breeder/sweep gas interface was examined, and main results are summarized in this paper. Platinum and palladium were deposited on solid breeder material pebbles (Li4SiO4) by the incipient wet impregnation method. Experiments were performed with hydrogen and predeuterated water using packed bed reactors and gas chromatographic analysis. Out of pile tritium release experiments were also conducted using ceramic breeders irradiated in a research reactor. The experimental results of this work reveal the benefit of the addition of catalytic additive metals, which is very effective to increase the tritium release rate from ceramic breeder materials especially at comparatively lower temperatures.