Effect of water vapor on tritium release from ceramic breeder material

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 the recovery of tritium from blankets over a wide range of temperature, the effect of the difference in sweep gas composition was investigated. Out of pile tritium release experiments were conducted using the ceramic breeders irradiated in a research reactor. The experimental results reveal the benefit of the sweep gas with water vapor, which is effective to increase the tritium release rate from ceramic breeder materials especially at comparatively lower temperatures. The experimental result was analyzed using several numerical models, and it was found that the consideration of trapping and detrapping reactions is necessary to reproduce the experimental tritium release curve.