Separation/enrichment of hydrogen isotopes by Zr-alloy getters

Safe handling and/or processing techniques, consisting of storage, supply, recovery, isotope separation and so on, are indispensable for research and development of thermonuclear fusion reactors. Nonevaporable getters have wide applicability for those kinds of processings. From this viewpoint, we have studied activation processes, absorption and desorption of hydrogen isotopes including isotope effect by using Zr-alloys as a model system. It was found that the kinetic isotope effect on the absorption process was considerably large for the Zr67Ni33 getter. On the basis of this observation, we studied the enrichment/separation of hydrogen isotopes. It was observed experimentally that a mixture of hydrogen and deuterium (H:D=57:43) changed its composition to H:D=53:47 by passing the mixture gas through Zr67Ni33 column held at liquid nitrogen temperature. Namely, deuterium was enriched in the gas outflow from the column. Similar results were observed with computational simulation using the experimentally observed rate constants for hydrogen and deuterium, indicating that the present simulation is fairly reliable. Further simulation revealed that hydrogen isotope mixtures such as H:D=1:1 and D:T=1:1 change their composition to H:D=1:9 and D:T=1:4, respectively, in the outflow gas with passing those gases repeatedly in the column at liquid nitrogen temperature. This indicates that hydrogen isotope separation is possible by application of the kinetic isotope effect. The present method has high potentiality because of it is safe, economical and simple to operate as well as having high separation efficiency. (author)