Tritium and Fuel-Cycle Control
A D-T device must recover, purify, and re-inject its fuel while accounting for every gram of tritium, all under continuous control.
The closed loop
Deuterium-tritium fuel is injected into the plasma, but only a small fraction burns per pass, so most fuel is exhausted, pumped out, and must be recycled. The fuel cycle is a controlled loop: exhaust gas is pumped, impurities and helium ash are separated, hydrogen isotopes are purified and re-mixed to the right ratio, and the fuel is returned to storage and the injectors.
Isotope separation and blending
The exhaust contains deuterium, tritium, helium, and protium along with impurities. Isotope separation, historically by cryogenic distillation, recovers pure deuterium and tritium streams. Control blends them to the deuterium-tritium ratio the plasma scenario needs and manages the storage beds that hold tritium as a metal hydride between pulses.
Accounting and control
Because tritium is radioactive and precious, its inventory is tracked through every stage as a control and safety requirement. Flow, pressure, and composition sensors feed an accounting system that must close the mass balance. Confinement barriers, glovebox pressures, and detritiation systems are actively controlled to keep tritium contained, with leak detection interlocked to safety systems.
- Recover and recycle unburned fuel each pulse
- Separate isotopes and blend the D-T ratio
- Store tritium on metal-hydride beds
- Track inventory and hold containment barriers
Kronos context
The Hyperion breeder is designed to breed its own tritium in a surrounding blanket, with a modeled tritium breeding ratio of 1.8, so the fuel cycle must integrate bred tritium with recycled fuel. First tritium for the first-of-a-kind machine is targeted around 2030 in the program plan, following construction beginning in 2027; the machine is a design and simulation case, and no net-gain hardware claim precedes that milestone. The burner uses D-3He with a much smaller tritium role.
Fuel-cycle control is where plasma operation meets the strict discipline of tritium stewardship.