Half-Life and Inventory Management
Managing a tritium inventory means budgeting for continuous decay, processing losses, and lead times so the on-hand level never drifts below requirement.
- Primary drain
- Decay ~5.5%/yr
- Secondary drains
- Withdrawals, processing loss
- Buffer penalty
- Held stock still decays
An inventory that leaks by physics
Because tritium decays at ~5.5%/yr, inventory management is fundamentally different from managing a stable material. The on-hand quantity falls every day whether or not any is withdrawn for use. A management plan therefore tracks three drains at once: radioactive decay, operational withdrawals, and losses during storage and processing.
The make-up budget
To hold a target level, the annual make-up must at least equal decay plus net withdrawals plus losses. Under-supplying in any year erodes the level; the erosion compounds because next year's 5.5% is taken from a smaller base only if no make-up arrives. A domestic source sized to the steady-state make-up rate keeps the plan stable.
Lead time and buffers
- Decay continues during production, transport, and processing lead times.
- A buffer stock absorbs schedule slips but itself decays while held.
- Right-sizing the buffer trades holding losses against supply risk.
The practical lesson is that a bigger buffer is not a free hedge: every kilogram held loses ~5.5% of itself per year. Beyond a point, resilience comes less from stockpiling and more from a dependable, appropriately sized production rate. The breeder is studied as one contributor to that rate, reported at design-target level until FOAK provides measured output.
Sizing the plan to steady state
A sound inventory plan is anchored to a steady-state make-up rate: the production needed to offset decay plus average withdrawals plus processing losses. Buffers ride on top of that rate to absorb schedule slips and demand spikes, but they are sized deliberately because every held kilogram loses ~5.5% of itself each year. The discipline is to make the production rate the primary hedge and the buffer a secondary one, rather than trying to substitute a large, decaying stockpile for a dependable source. The breeder is studied as a contributor to that steady-state rate.
This inventory logic is identical whether the isotope serves the stockpile, fuels a fusion fuel cycle, or supplies industrial users; only the target level and withdrawal rate change.