Fueling and Pellet Injection

Frozen fuel pellets and gas puffing replenish deuterium and tritium in the burning core and control the plasma density.

Feeding the reaction

A burning plasma consumes deuterium and tritium and must be continuously refueled. Two methods do this: gas puffing at the edge, which is simple but penetrates shallowly, and pellet injection, which fires small frozen pellets of hydrogen-isotope ice deep into the plasma where they ablate and deposit fuel in the core. Core fueling is far more effective for sustaining density where the fusion rate is highest.

Density control

Fueling is also the primary lever on plasma density, which sets the fusion power together with temperature. The design must maintain the density profile that supports 85.0 MW without exceeding density limits that would degrade confinement or trigger instabilities. Pellet timing, size, and speed are tuned to hold the core density while gas puffing manages the edge and the divertor.

Tritium and inventory

Because the fuel includes tritium, fueling ties directly into tritium inventory management: only a small fraction of injected fuel is burned per pass, so unburned tritium must be pumped, recovered, and recycled. Efficient core fueling reduces the tritium throughput needed for a given fusion output, which eases the inventory the machine must hold. Fueling efficiency is therefore both a performance and a tritium-economy question in the breeder.

• Pellet injection fuels the core; gas puffing serves the edge
• Fueling sets and controls plasma density
• Unburned tritium is recovered and recycled

Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030.