Proposal for a Concept of Heavy Water–Cooled Blanket and Preliminary Study of Suitable Water Detritiation Systems

This study proposes the concept of a heavy water–cooled blanket (HWCB), which is highly compatible with the direct internal recycling concept for the fuel cycle beyond the DEMO reactor. HWCB offers several advantages, such as eliminating the flow of protium from the water detritiation system (WDS) to the isotope separation system, improving the radiation safety of the WDS, and modestly increasing the tritium breeding ratio. A preliminary estimation of system scale was conducted on a WDS compatible with the HWCB concept for DEMO-scale coolant.For this study, the DEMO-scale coolant was assumed to have a tritium concentration of 370 GBq/kg and a flow rate of 6.6 metric ton/h. The primary isotope separation technologies examined were vacuum distillation (VD), electrolysis (EC), vapor phase catalytic exchange (VPCE), liquid-phase catalytic exchange, and combinations thereof. The stagewise model calculation at steady state showed that combining VD and EC was feasible. This system required a VD column sized at 6 m in diameter and 88.6 m in height, with an EC load of 1.83 mol/s and 524 kW. Replacing the EC with a six-stage VPCE also showed promise.