Tritium Losses and Holdup
Bred tritium is not all recoverable: decay, permeation, and holdup in walls and processing lines subtract from the surplus available as product.
The gap between bred and shipped
Net product is always less than gross breeding. Between the neutron captured on lithium-6 and the tritium loaded into a shipping container, several loss mechanisms act, and each one is subtracted from the surplus that the ~4 kg/yr class and the helium-3 coproduct depend on.
The loss mechanisms
- Radioactive decay: ~5.47% of held tritium per year becomes He-3 (recovered as coproduct, but lost as tritium)
- Permeation: tritium diffuses through hot metal walls and must be contained and recaptured
- Holdup: tritium trapped in blanket material, first wall, pumps, and getters
- Processing inefficiency: incomplete extraction and purification
- Streaming and leakage losses in the vacuum and fuel systems
Holdup is particularly important for a foundry because tritium sitting in the machine is tritium that is neither shipped nor available to burn, and it steadily decays. Minimizing standing inventory and residence time keeps more of the bred tritium available as product.
Loss budget and the gate
The loss budget is what separates a promising local TBR from a self-sufficient net TBR with saleable surplus. A machine can breed above 1.0 locally and still fail to ship product if holdup and losses are large. Quantifying and bounding these losses is part of the open self-sufficiency question, verified by measured inventory at FOAK.
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.