Fission Fusion Hybrid
We are performing conceptual design studies on a subcritical fission fusion hybrid reactor, which could reuse and reduce the waste of long-lived portions of spent nuclear fuel through minor actinide (MA) burning. Such a concept could use a relatively near-term fusion reactor as a high intensity neutron source such as WHAM++ or BEAM. With compact fusion devices with powers on the order of 1MW, a fission power optimized design can achieve a Tritium Breeding Ratio (TBR) of over 40, MA burnup of 200 kg/year, and 500MWth of blanket heating all while operating at ~10βeff below critical. This project includes a broad range of nuclear topics such as the fission and fusion nuclear fuel cycles, economics of advanced reactors, neutronics and thermal-hydraulics design of advanced reactors, and fusion energy technology.
A mixture of deuterium (H-2) and tritium (H-3) is the most commonly pursued fusion fuel for energy applications due to relatively low temperatures and pressures needed for high fusion reaction rates. Deuterium is relatively common in seawater, but tritium has a relatively short half-life of 12.3 years and kg scale quantities are only currently available through production in existing fission facilities. D-T fusion facilities use about 56 kg/GW-year, so Fusion Power Plants (FPPs) plan to produce their own tritium, but startup of new FPPs may still be limited due to limited tritium supply.
Initially facilitated through the Fission-Fusion Hybrid (FFH) project, the fission fuel cycle code CYCLUS was applied to fusion fuel cycles through the introduction of the TRICYCLE archetype. CYCLUS allows for flexible modular modelling of complex systems with multiple facility types, which allows for the modelling of an uncertain fusion future with fission tritium production, fusion demonstrators, and FPPs with vastly varied characteristics. Examples of outputs are shown on the right, including the available commercial tritium supply with and without commercial and ITER sinks as well as the startup of 2GW DEMO-like FPPs with and without external sources of tritium.
