Influence of hydrogen addition to a sweep gas on tritium behavior in a blanket module containing Li₂TiO₃ pebbles

Hydrogen addition to a sweep gas of a solid breeder blanket module has been proposed to enhance tritium recovery from the surface of the breeders. However, the influence of hydrogen addition on the bred tritium behavior is not understood completely. Tritium behavior in the simplified blanket module of Li₂TiO₃ pebbles was numerically calculated considering diffusion in the grain bulk, surface reactions on the grain surface and permeation through the cooling pipe. Although a partial pressure of T₂ increases with increasing a partial pressure of H₂ in the sweep gas, it was estimated that tritium permeation rate to the cooling water decreases. Additionally, the release duration of water vapor generated by the reaction of the pebbles and hydrogen is shortened with increasing a partial pressure of H₂. Tritium inventory in the grain bulk and the grain surface occupies 99.6 % of total tritium inventory in the blanket module.