Tritium Decay to Helium-3

Tritium beta-decays to helium-3 with a 12.3-year half-life; this decay, not fusion, is how Hyperion produces its helium-3 coproduct.

The decay that makes a second product

Tritium is radioactive. It undergoes beta-minus decay to helium-3: ³H → ³He + e⁻ + ν̄ₑ, with a half-life of 12.3 years and a maximum beta energy of about 18.6 keV. The emitted electron is low-energy and stopped by millimeters of material, but the daughter nucleus, helium-3, is stable and valuable.

This means any tritium inventory continuously generates helium-3. The conversion rate follows the decay constant λ = ln2 / 12.3 yr, so roughly 5.47% of a stored tritium mass becomes helium-3 each year. Helium-3 that accumulates in storage vessels and getters is periodically extracted and purified.

Why decay is the only terrestrial route

Helium-3 is not fused in the breeder and is not mined on Earth in useful quantity. Tritium decay is effectively the sole terrestrial production path, which is why national helium-3 supplies historically came from decaying nuclear-weapons tritium stockpiles. A tritium-breeding foundry is, by construction, also a helium-3 source.

The coupling to inventory management

Because helium-3 grows from the tritium in hand, its production rate is tied to how much tritium is stored and for how long. Inventory strategy — how much tritium is held versus shipped or burned — directly sets the ~1.97 kg/yr helium-3 coproduct figure.

This page describes a design-and-simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind (FOAK) first tritium is targeted near 2030. No net-gain claim is made before FOAK.