To develop a tritium monitoring system with a membrane gas separator, the extraction characteristics of a hydrogen isotope pump using CaZr0.9In0.1O3- as proton conductor were evaluated over the temperature range from 873 K to 1073 K by electrolysis of tritiated water vapor. Although the isotope ratio between proton and tritium in the anode compartment was extremely low, tritium gas (HT) could be extracted along with hydrogen gas (H2) to the cathode compartment by the electrochemical hydrogen pump. The T/H isotope ratio in the cathode compartment was lower than that in the anode compartment because of the isotope effect in the hydrogen pump. However, when the hydrogen recovery rate increased, the ratio of hydrogen isotopes approached unity, which might be caused by variation in the T/H ratio along the axial direction. With respect to the tritium memory effect in the proton conductor, the isotope exchange reaction using wet gas was found to be an efficient method for tritium decontamination.