JAERI has been developing an improved compact tritium gas enrichment/recycling system to handle relatively smaller amount of tritium for efficient researches on tritium processing and development work. An electrochemical hydrogen pump based on CaZr0.9In0.1O3− α proton conductor is investigated to separate hydrogen isotopes directly from inert gas carrier after the enrichment process of the system. The prototype hydrogen pump was developed for the first time to operate under vacuum condition at the cathode compartment, and the performance test was carried out.