Startup Tritium Inventory
A breeder cannot breed before it runs, so the first machine needs an external tritium charge to start — the startup inventory problem.
The chicken-and-egg of first fuel
Tritium breeding requires a running D–T plasma, but running a D–T plasma requires tritium. The first unit therefore needs a startup inventory of tritium sourced externally before it can breed its own. This is the startup inventory problem, and it is a real constraint on how a fusion fleet can grow.
Today external tritium comes from fission reactors in limited quantity. FOAK Hyperion is expected to draw on such supply to begin operation near 2030, then transition toward breeding its own fuel. Whether it can also breed enough surplus to charge the next unit is set by the net TBR.
Why net TBR governs fleet growth
Once a machine is self-sufficient, only the surplus above self-sufficiency is available to start additional units. A net TBR of 1.1 leaves almost none; 1.5 and 1.8 leave progressively more. The higher the net TBR, the faster a fleet can double, because each machine can seed the next sooner. This is the doubling-time argument for targeting 1.8.
A stated dependency
- FOAK requires external startup tritium (near 2030)
- Self-sufficiency lets a unit sustain itself
- Surplus above self-sufficiency seeds new units
- Net TBR sets how quickly the fleet can grow
The startup charge and the surplus economy are design-and-simulation planning, contingent on the self-sufficiency gate.
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.