Tritium decays into helium-3 at a fixed rate — about 0.42 litres of helium-3 per gram of tritium per year. A tritium stockpile is therefore a helium-3 source that ripens on its own, which is one of the ways the breeder seeds the burners' fuel.
Tritium's 12.3-year half-life means a stockpile continuously converts to helium-3. The Kronos record carries the corrected, deposited accrual figure of 0.42 L of helium-3 per gram of tritium per year. Terrestrial tritium-decay stockpiles are thus a real, if slow, helium-3 source that requires no new physics to exploit.
Decay accrual is the most reliable helium-3 source there is, because it is just physics running on its own clock. It is one leg of a staged supply strategy — stockpile decay, in-plant breeding, and external reserves — that is resilient to any single source disappointing.
| Accrual rate | ~0.42 L He-3 / g tritium / yr |
| Mechanism | tritium decay (12.3-yr half-life) |
| Source type | terrestrial stockpiles |
| New physics required | none |
| Role | one leg of staged supply |