Deep Dive: Fuelling & Exhaust

A burning plasma must be continuously fed and cleaned — fuel injected to the core, helium ash and unburned fuel pumped out and recycled at over 95% single-pass.

Fuel in

Pellet injection to the dense core

Ash out

Helium exhausted via the divertor

Recovery

> 95% single-pass DIR (P4)

Balance

Feed rate matched to burn + exhaust

A steady fusion burn is a continuous flow problem: fuel must go in as fast as it's consumed, and spent fuel and helium ash must come out just as fast, without disturbing the plasma.

Fuelling. Because edge gas puffing barely reaches the core, Kronos uses pellet injection — firing frozen fuel pellets deep into the plasma to maintain the high core density (n̄_e = 1.9 × 10²⁰ m⁻³) and deliver the right D–³He mix.

Exhaust and recycling. Helium ash and unburned fuel flow through the scrape-off layer to the divertor, where they're pumped out. The fuel is then recycled by direct internal recovery at over 95% single-pass (prediction P4) — keeping the working fuel inventory small and the ³He mass balance tight.

Getting this feed-and-clean loop right is essential to steady-state operation, and it ties together fuelling, the divertor, and the fuel cycle into one system.