Fusion fuel processing systems are expected to rely on multi-column, cryogenic distillation systems for separating hydrogen isotopes. These systems will run continuously and need to respond to feeds varying considerably in both composition and flowrate. These systems will also need to operate with minimal inventories due to the value and safety concerns associated with tritium. These factors result in a clear need for a system of automatic control to maintain the isotope separation system operating properly. Such a system of regulatory (or material balance) controls have been added to the four-column ISS at the Tritium Systems Test Assembly. These controls have been tuned and tested individually. Then the overall system was demonstrated to work successfully. The results of this work is reported in this paper.