Why does Kronos build two different machines?

The breeder and burner do different jobs, so they use different fuels and geometries. The spherical-tokamak breeder makes neutrons, tritium and helium-3; the tandem-mirror burner converts D–³He directly to electricity. 'Fuel follows purpose, not platform.'

Building the breeder first gives Kronos a saleable product — isotopes and neutrons — before the hardest net-electric milestone is reached.