A continuous membrane column process that uses a palladium alloy membrane for the separation of hydrogen isotopes is studied. Hydrogen, deuterium, and tritium permeation rates obtained in previous studies are used in numerical calculations in which the nature of the membrane column is investigated through variations in the operation variables, such as the pressures and their ratio, the reflux ratio, and the stripping column velocity. Finally, a cascade design in which membrane columns are used as unit cells is developed, following a design study of a nuclear fusion reactor fuel cycle system, and the concentrations and flow rates are calculated. The results show that hydrogen, deuterium, and tritium can be separated and concentrated as well by this method as by the liquid hydrogen distillation process. The inventory of the membrane column process is also calculated, and it is ∼2.3 times the fuel processed in a day.