World’s first fast-neutron nuclear reactor to power AI data centers

French startup Stellaria has secured its first power reservation from Equinix for Stellarium, the world’s first fast-neutron molten-salt nuclear reactor designed to reduce nuclear waste. Stellarium is a fourth-generation reactor using liquid chloride salt fuel in a closed fuel cycle, capable of destroying more long-lived nuclear waste than it produces—a milestone no commercial reactor has yet achieved. The compact reactor, occupying only four cubic meters, can utilize a wide range of nuclear fuels including uranium, plutonium, MOX, minor actinides, and thorium. Stellaria aims to achieve its first fission reaction by 2029 and begin commercial deployment by 2035. Key design features include passive cooling, four physical containment barriers, and operation for over 20 years without refueling, making it a safe, resilient, and scalable clean energy source. The agreement with Equinix will enable the company’s AI data centers to operate autonomously with carbon-free, controllable nuclear power, supporting sustainable and dec