Fuel Accountancy

Because helium-3 is scarce and bred, every gram is tracked through a mass-balance system spanning breeder, store, burner, and exhaust recovery.

Accounting for a bred resource

When a fuel is abundant, you meter it; when a fuel is bred slowly and cannot be quickly replaced, you account for it. Helium-3 falls in the second category. A fuel-accountancy system maintains a mass balance across the whole loop: helium-3 produced at the breeder, held in store, injected into the burner, burned, and recovered from exhaust. The books must close — helium-3 in must equal helium-3 burned plus helium-3 returned plus known losses.

Why the books must close

A closed mass balance does two jobs. Operationally, it tells the fleet how much helium-3 is available and how far the reserve can stretch, feeding the inventory-management plan. It also provides material accountancy: because helium-3 comes from tritium, the same discipline that tracks a strategic, bred isotope for supply purposes supports the safeguards and reporting expected of any tritium-derived material.

• Mass balance across breeder, store, burner, and exhaust
• Books must close: in = burned + recovered + losses
• Feeds inventory management and fleet planning
• Supports safeguards for a tritium-derived material

Accurate accountancy depends on the fuel-cycle instrumentation — flow, composition, and inventory measurements at each node — which is why measurement and accounting are treated together in this section.