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Question
Does D–³He fusion produce neutrons?
The primary D–³He reaction is aneutronic, but side D–D reactions make some neutrons — which is why Kronos says 'low-neutron,' not 'aneutronic.'
This is the most common — and most important — question about the Kronos fuel choice, and the answer is a
careful one. The headline reaction Kronos targets, D + ³He → p + α, produces only charged particles and
is aneutronic. But in any real plasma hot enough to burn D–³He, deuterium also reacts with itself, and one of
the two D–D branches emits a neutron. A working D–³He plant is therefore low-neutron, not neutron-free.
Why the distinction matters: fewer neutrons means far less structural activation, a smaller shield, less
material damage, and — critically — that most of the energy emerges as charged particles that
direct energy conversion can capture. Kronos deliberately avoids
the word "aneutronic" for the commercial machine and reserves it for the gated p–¹¹B endpoint.
Questions & answers
Does D–³He fusion produce neutrons?
The primary reaction, deuterium + helium-3 → proton + alpha, is aneutronic — both products are charged. But a real D–³He plasma also runs side deuterium–deuterium reactions, and one D–D branch releases a neutron. So a practical D–³He plant is low-neutron, not neutron-free. Kronos states this plainly and uses the term 'low-neutron' rather than 'aneutronic.'
How many neutrons, compared to conventional fusion?
The neutron power fraction of the Kronos MetroVolt design point runs at about 5.25% along the fuel schedule (up to ~7% at other stages) — versus roughly 80% for a deuterium–tritium plant. That is neutron loading on the order of 25× below D–T.
Is any Kronos fuel truly aneutronic?
Only the gated proton–boron-11 (p–¹¹B) endpoint is genuinely aneutronic. It sits at the far end of the staged fuel roadmap and is treated as a gated research endpoint, not the commercial baseline.