Evaluation of Tritium Confinement Performance of Alumina and Zirconium for Tritium Production in a High-Temperature Gas-Cooled Reactor for Fusion Reactors

Tritium production utilizing nuclear reactions by neutron and lithium in a high-temperature gas-cooled reactor is attractive for development of a fusion reactor. From viewpoints of tritium safety and recovery efficiency, tritium confinement is an important issue. It is known that alumina has high resistance for gas permeation. In this study, hydrogen permeation experiments in commercial alumina tubes were conducted and hydrogen permeability, diffusivity and solubility were evaluated. By using obtained data, tritium permeation behavior from an Al₂O₃-coated Li-compound particle was simulated. Additionally, by using literature data for hydrogen behavior in zirconium, an effect of Zr incorporation into an Al₂O₃ coating on tritium permeation was discussed. It was indicated that the majority of produced tritium was released through the Al₂O₃ coating above 500 °C. However, it is expected that total tritium leak is suppressed to below 0.67 % of total tritium produced at 500 °C by incorporating Zr fine particles into the inside of Al₂O₃ coating, assuming tritium pressure inside particle is kept at the plateau pressure of the Zr hydride generation reaction.