Recovery of Tritium in Inert Gas by Precious Metal Catalyst Supported by Hydrophilic Substrate

In this study, it is proposed to use exchange reaction between hydrogen isotopes in gas phase and those in hydrophilic substrate of the precious metal catalyst for the purpose of recovering tritium as molecular form from the inert gas such as the atomosphere in the secondary containment, where no oxygen is expected. The values of the equilibrium constant and reaction rate constant for this reaction are obtained for tritium-protium system and deuterium-protium system experimentally. It is also certified that the tritium concentration at the outlet of Pt-alumina catalyst bed is evaluated in good agreement with experimental values. Behaviors of the tritium cleanup system for the secondary containment applying this reaction are compared for various operational conditions, and it is concluded that isotope exchange reaction using hydrophilic catalyst bed is applicable for the secondary contaiment. The bed of the precious metal catalyst can also be active as oxidation catalyst even when air in the tertiary containment is introduced by some accidents.     

Catalytic Oxidation of Tritium in Wet Gas

Use of precious metal catalyst is recommended in the tritium recovery system because it can oxidize tritium at ambient temperature. The ability to operate at the ambient temperature without preheating and past cooling is a large advantage in the ease of system operation. It is observed in this study, however, that the catalytic oxidation characteristics of the precious metal catalysts are largely affected by the water vapor to such extent that almost no oxidation rate of tritium is expected in the wet gas. Effect of the water vapor on the oxidation rate is quantitatively discussed based on data obtained in this study and an emergency cleanup system from the room air with pre-adsorption bed is proposed.