Loss-of-Coolant Response

With no large decay-heat source, losing coolant does not lead to core damage — the structure stays below its limits passively.

The loss-of-coolant accident is the defining severe-accident scenario for water-cooled fission plants, precisely because decay heat must be removed for days after shutdown. Remove the coolant and temperatures climb toward fuel damage. The scenario's severity is set by the size of the residual heat source.

Why the fusion case is bounded

When a fusion plasma terminates, the only remaining heat is decay heat in activated structures — the vessel, first wall, and blanket. This inventory is small, and it decays quickly compared with fission fuel. The relevant question is whether structures can shed that heat by conduction and radiation alone; for Kronos geometries and power levels, they can, keeping materials below damage thresholds.

The burner (Aegis / MetroVolt) has an advantage here: its 5.44% neutron fraction means less activation, less decay heat, and a smaller temperature rise. Its direct energy conversion also means it does not depend on a large steam-cycle coolant loop in the first place — see why fusion cannot melt down.

Design consequences

• Coolant is for productive heat removal in normal operation, not for averting core melt.
• Passive heat paths are sized so no active makeup cooling is credited for safety.
• Loss of coolant is an equipment-protection concern, not a public-safety cliff.

This reframes coolant systems from safety-critical to operationally important, which is a large simplification of the accident analysis and the required safety-grade systems.