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Comparison
D–³He vs D–T Fuel
Deuterium–helium-3 versus deuterium–tritium: fewer neutrons, direct energy conversion, and a harder ignition problem. A side-by-side for the Kronos choice.
- Neutron fraction
- D–³He 7.70% (Kronos, operating) vs D–T ~80%
- Conversion
- D–³He enables direct energy conversion; D–T is thermal
- Difficulty
- D–³He needs higher temperature / better confinement
- Fuel supply
- D–T needs tritium breeding; D–³He breeds ³He in situ
Almost every fusion program burns deuterium–tritium (D–T) because it ignites most easily. Kronos chose deuterium–helium-3 (D–³He) instead. The trade is deliberate.
| Property | D–T / D–³He (Kronos) |
|---|---|
| Ease of ignition | D–T ignites at lower temperature; D–³He demands higher temperature and better confinement (H₉₈ = 2.28) |
| Neutron output | D–T ~80% of energy in neutrons; D–³He low-neutron, 7.70% at the Kronos operating point (≈10× lower) |
| Energy capture | D–T is neutron-heavy → thermal steam cycle; D–³He is charged-particle-rich → direct energy conversion |
| Materials / shielding | D–T drives heavy activation, large shield, 33–42% availability penalty; D–³He far lighter |
| Fuel supply | D–T needs on-site tritium breeding; Kronos breeds ³He in situ via a catalyzed D–D cycle |
The honest cost of the D–³He choice is a harder plasma-physics problem: higher temperatures and a demanding confinement requirement (the hot-ion posture is retained only as a gated ceiling). Kronos accepts that in exchange for a directly convertible, low-neutron output — and prices the physics bet openly at the gates.
Honest gapThe D–³He advantage is contingent on meeting the confinement requirement (H₉₈ = 2.28 at the Mode-D baseline), with the hot-ion ceiling gated on the fast-ion channeling demonstration. Kronos plans to the near-thermal baseline and treats the hot-ion ceiling as earned upside.