Simulation and Optimisation of Cryogenic Distillation and Isotopic Equilibrator Cascades for Hydrogen Isotope Separation Processes in the Fusion Fuel Cycle

Hydrogen isotope separation is a critical component of the fusion fuel cycle, particularly for achieving the desired purity levels of deuterium and tritium while minimising tritium inventory. This study investigates the cryogenic distillation of hydrogen isotopes, with a focus on the effects of isotopic equilibrium reactions at reduced temperatures and different system configurations. A one-column architecture was analysed to evaluate the impact of feed and side stream equilibrator temperatures and flowrates on separation performance and tritium inventory. Additionally, a two-column architecture was studied, incorporating multiple isotopic equilibrators in interconnecting streams, to further reduce unwanted heteronuclear isotopologues and improve system efficiency. Comparative analysis of the proposed configurations highlights significant operational advantages of optimising equilibrator temperatures, including reduced tritium contamination and inventory. Results indicate that reducing equilibrator temperatures to 77.4 K not only improves separation efficiency but also enables reductions in the number of theoretical stages required, minimising tritium inventory. A case study of the ITER Isotope Separation System demonstrates that reducing equilibrator temperatures achieves comparable performance with fewer stages in key columns, validating the benefits of optimised equilibrator operation for practical application. These findings contribute to the development of more efficient, cost-effective designs for fusion fuel cycle isotope separation systems.