Kairos Power's KP-FHR is a molten-fluoride-salt-cooled, TRISO-fueled reactor — a non-light-water design backing Google's AI power bet

Google's nuclear bet for AI data-center power runs through Kairos Power, whose reactor — the KP-FHR (Kairos Power Fluoride salt–cooled High-temperature Reactor) — is mechanically unlike the conventional light-water plants that dominate the US fleet. Per the US Department of Energy, the design is a "140 megawatt-electric high-temperature molten salt reactor" cooled by "FLiBe (a mixture of lithium and beryllium fluoride salts)" and fueled with "robust TRISO fuel" particles.

Three design features distinguish it from a pressurized- or boiling-water reactor:

• Coolant. FLiBe molten salt, not water. The salt is liquid across a wide temperature band and operates near atmospheric pressure, so the reactor avoids the high-pressure steam envelope that drives much of a light-water plant's containment engineering.
• Fuel. TRISO (TRi-structural ISOtropic) particles encapsulate fuel kernels in layers of carbon and ceramic engineered to retain fission products at high temperature — a fundamentally different fuel form than the zirconium-clad uranium rods of a light-water reactor.
• Regime. High outlet temperature at low pressure, targeting passive safety margins.

This makes Google's path a genuine engineering fork from Microsoft's light-water restart of Three Mile Island Unit 1: one company is reviving a legacy design, the other is fielding a novel one. Both are downstream of the same driver — the continuous power demand of AI inference. Molten-salt and non-conventional reactor concepts also appear in the vault's reactor-engineering cluster, e.g. the direct-cycle reactor modeling of the Burevestnik.