Neutron Activation

Neutron activation is how fusion neutrons make structures mildly radioactive. A low-neutron design minimizes it — Kronos's central materials advantage.

What

Neutrons transmuting structure into radioisotopes

Fusion vs fission

No long-lived spent fuel; far less waste

Kronos lever

Low neutron fraction (~5.25%)

Benefit

Smaller shield, less damage, shorter-lived waste

Neutron activation is the process by which neutrons striking a reactor's structure convert some atoms into radioactive isotopes. It is the main source of radioactive material in a fusion plant — not spent fuel, as in fission, but activated steel and components. The amount scales directly with the neutron flux the structure sees.

This is exactly where the Kronos low-neutron D–³He choice pays off. With a neutron fraction around 5.25% — roughly 25× below deuterium–tritium — activation, shielding mass, and material damage are all dramatically reduced, and the waste that does form is shorter-lived. The design still carries an explicit neutron-fluence budget for the shielded center stack, because even a low flux, over 30 full-power-years, must be accounted for.