Hyperion burns deuterium-tritium while Aegis and MetroVolt burn deuterium-helium-3. That is not inconsistency; it is the programme's governing rule — fuel follows purpose, not platform.
A pressure-limited spherical tokamak wants reactivity, and D-T is the most reactive fuel; its high reactivity lets Hyperion reach its fusion conditions at a much lower plasma current than a less reactive fuel would need. Buildability wins, so the breeder burns D-T. The burners, whose product is clean electricity, choose D-3He to suppress neutrons.
Matching fuel to mission is why one company can field both a neutron-rich foundry and a low-neutron generator without contradiction. The rule keeps each machine honest about why it burns what it burns.
| Breeder fuel | D-T (reactivity, buildability) |
| Burner fuel | D-3He (low-neutron electricity) |
| Rule | fuel follows purpose, not platform |
| Why D-T for the breeder | highest reactivity -> lower current |
| Why D-3He for the burner | suppresses neutrons |