Low-Neutron, Not Aneutronic

We hold a firm line on language: D-³He fusion is low-neutron. Any claim of zero neutrons would be false.

“Aneutronic” is a word that has been stretched in fusion marketing. Strictly, it means a reaction that emits no neutrons. Pure proton–boron-11 fusion approaches this ideal. D–³He does not, because a deuterium plasma always undergoes some D–D fusion, one branch of which produces a neutron directly and another branch of which produces tritium that fuses with deuterium to make a 14 MeV neutron.

For the burner design point, the neutron channel carries 5.44% of fusion power. That is why every Kronos document calls the machine low-neutron and never aneutronic. The difference is not pedantry: it determines whether a reader expects zero shielding and zero activation, which would be wrong.

What honesty buys us

Stating the neutron fraction plainly lets engineers size shielding correctly and lets regulators and neighbors trust the rest of the safety case. A machine that admits its 5.44% neutron channel is more credible than one that hides it behind a marketing label. The activation, waste, and worker-dose consequences all follow from this number and from the breeder's much larger 14 MeV flux.

Independent verification also depends on this candor: a device claimed to be aneutronic invites disbelief, because reviewers know deuterium plasmas make neutrons. Publishing the 5.44% figure and its origin lets others check the calculation against the same cross-sections and reproduce it, which is worth more to credibility than any label.

This is a design-and-simulation position. The burner is not built; the 5.44% figure is a modeling result for the frozen design point. If a future device measured a different fraction, the language would follow the physics, not the other way around.