We already have the world’s first fast neutron nuclear reactor. We are going to use it for AI data centers

The growth of artificial intelligence is driving global electricity demand to historical figures. The expansion of data centers, the advance of electrification and the industrial rebound are straining aging networks that are already suffering from saturation in multiple countries.

In this scenario, the digital sector—a large consumer of electricity for the development of AI—faces a paradox: it needs much more energy, but it must do so without increasing its emissions. And there arises a proposal that until recently would have seemed like science fiction: data centers powered by a compact fast neutron nuclear reactor.

The Stellaria–Equinix deal that no one saw coming. The French startup Stellaria, born from commissariat to the atomistic energy (CEA) and Schneider Electric, announced a pre-purchase agreement with Equinix, one of the largest global data center operators.

According to the press releasethe agreement secures Equinix the first 500 MW of capacity of the Stellarium, the molten salt and fast neutron reactor that the company plans to deploy starting in 2035. This reserve is part of Equinix’s initiatives to diversify towards “alternative energies” applied to AI-ready data centers.

Autonomy, zero carbon and waste management. It is a brief summary of the first reactor breed and burn intended to supply data centers. As explained by Stellariaoffers:

• Completely carbon-free and controllable energy, enough to make a data center autonomous.
• Underground design without exclusion zone, thanks to its operation at atmospheric pressure and its liquid core.
• Ultra-fast response to load variations, essential for generative AI.
• Virtually infinite regeneration of fuel, part of which can come from current waste from nuclear power plants.
• Multi-fuel capability, from uranium 235 and 238 to plutonium 239, MOX, minor actinides and thorium.

For Equinix, this means solving one of its great challenges: operating with guaranteed clean energy 24/7 without depending on the grid. For Europe, it marks the entry into a new generation of ultra-compact reactors: the Stellarium occupies just four cubic meters.

The technology behind the reactor. The Stellarium is a fourth-generation liquid chloride salt reactor, cooled by natural convection and equipped with four physical containment barriers. It operates on a closed fuel cycle, capable of maintaining fission for more than 20 years without recharging.

Stellaria’s roadmap establishes that in 2029 there will be the first fission reaction and six years later a commercial deployment and delivery of the reactor to Equinix. According to the company, The energy density of this type of reactor is “70 million times higher than that of lithium-ion batteries”, which would allow a single Stellarium to supply a city of 400,000 inhabitants.

As fusion progresses, fast fission arrives first. To understand why a fast neutron reactor comes to the world of AI before fusion, just compare the technological moment of each. The merger is making spectacular progress—such as the record of the French WEST reactorwhich maintained a stable plasma for 22 minutes, or the Wendelstein 7-Xwhich sustained a high-performance plasma for 43 seconds—but remains experimental. ITER will not be operational this decade and commercial prototypes will not arrive until well into the 2030s.

Advanced fission, on the other hand, is much closer to the market. Reactors like Stellaria’s, with molten salt and fast neutrons, do not require the extreme conditions of fusion and can be deployed sooner. The company plans its first reaction in 2029 and a commercial deployment in 2035.

The data centers of the future will no longer depend on the network. Equinix already operates more than 270 data centers in 77 metropolitan areas. In Europe they are powered by 100% renewables, but their future demand for AI will require a constant, carbon-free source that does not congest the electrical grid. According to Stellariathis agreement “lays the foundation for data centers with lifetime energy autonomy.” And, if the company meets its schedule, Europe will become the first region in the world where artificial intelligence is powered by compact reactors that recycle their own nuclear waste.

The technological race between advanced fission and fusion is far from over, but, today, the first fast neutron reactor intended for AI does not come from ITER or an industrial giant: it comes from a French startup. Europe has just opened a door that could transform, at the same time, the future of energy and computing.

Image | freepik and Stellaria

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