The separation of hydrogen isotopes is a vital step in preparing tritium and deuterium fuels for future fusion energy plants. This represents a fundamental challenge to fusion energy since the separation process must be able to handle high throughputs of hydrogen isotopes with a low tritium inventory, as tritium is highly radioactive and hazardous. There are many possible isotope separation techniques, however none that are currently deployable can meet the demands required. For the first time in the open literature a comprehensive review of 13 hydrogen isotope separation technologies is given, to understand the development route to a process that addresses this key challenge of fusion energy.

Cryogenic distillation, a conventional separation technique, has high complexity and high tritium inventory in liquid phase. Gas phase processes have most potential to replace conventional tritium handling processes since the tritium concentrations are far lower than those which use liquid hydrogen compounds or liquid hydrogen. Recent developments have been made in new high-performance processes and isotope selectivity mechanisms including adsorbent separation based on quantum sieving and the Thermal Cycling Absorption Process (TCAP). Several other processes have received little development, and this article discusses which of these show promise, and the areas which require further research to make them successful for application in future fusion plants.