Fuel-Cycle Self-Sufficiency
A deuterium-tritium device must breed as much tritium as it burns; the breeder studies a breeding ratio above one to run its fuel cycle and leave a surplus.
Closing the fuel cycle
A deuterium-tritium plasma burns tritium continuously. Unless the device breeds tritium at least as fast as it burns it, the fuel cycle is not closed and the machine depends on external tritium indefinitely. Breeding with a TBR above 1 is what makes a device fuel-independent and, above a threshold, a net supplier.
Self-sufficiency plus export
A TBR near 1.1 targets self-sufficiency — replacing burned tritium plus losses. Higher values studied (1.5, 1.8) point toward a surplus beyond the machine's own needs, which is the basis for the tritium-class output referenced in the design set. The surplus, not the recycled fraction, is what serves external supply.
- TBR = 1: closes the cycle in principle, no surplus.
- TBR > 1: self-sufficiency plus a supply surplus.
- Real losses raise the TBR needed to stay net-positive.
An honest caveat
Reconciling a target TBR with realistic blanket coverage, neutron multiplication, and losses is an open engineering question. The 1.1/1.5/1.8 values are simulation levers, and net breeding performance is a result the machine must demonstrate rather than a settled fact.
Recycling is not surplus
It is worth separating two ideas that are easy to conflate. Recycling unburned fuel keeps a plasma running but does not by itself create exportable material; it merely avoids wasting what was already introduced. Only breeding above self-sufficiency generates genuinely new tritium beyond the machine's own needs. A device can have excellent fuel recycling and still be a net consumer if its breeding does not exceed its burn plus losses. The exportable quantity is the surplus from breeding, which is why the breeding ratio, not the recycle fraction, is the figure that governs external supply.
The breeder (Hyperion) — Construction begins Q2 2027; first-of-a-kind (FOAK) first tritium is targeted for ~2030. No hardware net-gain or delivered-isotope claim is made before FOAK.