Under the Annex IV of the US-Japan Collaboration Program, loop test of the TSTA was performed in October, 1990. This test is focused on the Isotope Separation System with 3 distillation columns operated. The system was stably operated and DT products were continuously obtained. Composition profile along the columns were successfully measured with the Gas Chromatograph. In the Fuel Cleanup System, amount of adsorbed tritium on the cold molecular sieve beds were measured and a large impact of this phenomena on inventory was revealed. (author).