A D-T plant sends about 80% of its energy out as 14 MeV neutrons; the burner's D-3He cycle sends 5.44% at its design point. That roughly order-of-magnitude difference in neutron budget is the single fork from which the two plants' entire designs diverge.
D-T's 14.1 MeV neutrons demand a meter-scale breeding blanket, activate the structure, and set a replacement clock. D-3He's charged-particle output needs none of that: no breeding blanket, a gentle wall, and a path to direct conversion. The burner pays a confinement price for the quiet fuel and buys a categorically different plant with it.
The neutron budget is not one design parameter among many; it decides the blanket, the wall life, the activation inventory, the maintenance cadence, and the licensing posture all at once. Kronos fields both fuels — D-T in the breeder, D-3He in the burner — because each budget suits a different job.
| D-T neutron budget | ~80% of energy |
| D-3He neutron budget | 5.44% (design point) |
| D-T requires | breeding blanket, frequent wall changes |
| D-3He requires | no blanket, gentle wall |
| Trade | quiet fuel for harder confinement |