Michael Heumann

The Fusion Report’s series on the critical supporting technologies for commercial fusion energy continues with power conversion and fuel management systems. In D-T fusion, the 14.1 MeV neutron carries roughly 80% of the total energy into a thermal blanket, where the resulting heat drives a turbine and generator, largely the same mechanism that has been used for over 140 years. Aneutronic approaches such as D-He3, backed by Helion Energy, and p-B11, planned by TAE Technologies, Marvel Fusion, and HB11 Energy, can use either the same thermal cycle or direct energy conversion, which has been demonstrated but is not production-ready yet. On the fuel side, MFE and hybrid D-T plants run a largely closed loop that pumps out unburned fuel and helium ash, purifies it, and reinjects it, while also breeding and recovering tritium from lithium blankets. IFE machines must inject frozen fuel pellets at rates of up to 10 Hertz and clear debris from the chamber between shots.

The Fusion Report continues its series on the critical supporting technologies for commercial fusion energy with a look at divertors and heat exhaust systems. Tokamaks such as ITER use X-point divertors with tungsten armor to pull helium ash, fuel ions, and heat out of the plasma edge, and reactor-scale designs are exploring snowflake and long-leg geometries such as Super-X to spread the heat load. Stellarators such as Wendelstein 7-X require island or helical divertor modules that conform to a three-dimensional magnetic field. Magnetic mirrors instead need engineered end regions, including expanders, cooled collectors, pumping, and possibly direct energy converters that recover part of the escaping particle energy as electricity. Inertial fusion machines need chamber and first-wall protection systems but no divertor in the classical sense, which makes heat exhaust primarily a magnetic fusion energy problem.

The Fusion Report continues its series on the challenges commercial fusion energy must overcome, this time examining fusion fuel and the systems that inject it into fusion machines. Despite claims that fusion fuel is essentially free, a hypothetical 1GW deuterium-tritium plant would burn roughly 100 grams of deuterium and 150 grams of tritium per day, with tritium costing roughly $30,000 per gram today, or about $1.6B per year, until breeding is proven. Even with breeding, the lithium-6 consumed annually would run roughly $20M per year, and the initial fill of a breeder blanket with 40 to 100 metric tons of enriched lithium could cost $1.6B to $4B at today’s prices. The article also compares fueling approaches across machine types: inertial fusion machines fire cryogenic D-T pellets at 1 Hz or faster, magnetic fusion machines inject D-T gas that is heated into a continuously fueled plasma, and hybrid systems such as Helion’s Polaris accelerate two plasma clouds into each other.