Equinix is betting that the next wave of digital infrastructure will be powered not only by renewables and grid contracts, but by advanced nuclear. The global data center giant has signed a pre-order agreement with French start-up Stellaria for electricity from its first commercial molten salt reactor, a compact unit branded ‘Stellarium’ that the company plans to deploy from 2035.
Under the arrangement, Equinix has reserved the first tranche of power capacity from a future Stellarium reactor, marking the inaugural capacity commitment Stellaria has secured. The deal is framed as a long-term move to secure firm, low-carbon power for Equinix’s growing fleet of AI-ready, high-density data centers, which are driving up both power demand and resiliency requirements worldwide.
Stellaria is a spin-out from the French Alternative Energies and Atomic Energy Commission (CEA), one of Europe’s leading nuclear research institutions. Its proposed molten salt reactor design is notably compact, at around four cubic meters of reactor core volume, and is intended to operate with a range of nuclear fuels including uranium, plutonium, MOX, minor actinides and thorium. Stellaria claims that Stellarium is the first reactor concept to run on a liquid fuel capable of “destroying more waste than it produces,” positioning it as a tool for both power generation and long-lived waste reduction.
Diversifying The Energy Mix
For Equinix, the agreement is part of a broader strategy to diversify its energy mix beyond traditional power purchase agreements and grid-based renewables. In August, the company announced partnerships with five alternative energy providers, including Stellaria, to support the expansion of its AI-optimized data centers. The Stellaria deal is the most futuristic of these moves, pointing toward a model in which some data center campuses may eventually sit alongside dedicated, on- or near-site nuclear microreactors.
Régis Castagne, Managing Director of Equinix France, said the company selected Stellaria because it is among a small group of vendors that could, in principle, make very high-density AI data centers both energy-resilient and low-carbon. Stellarium units are designed to generate around 250 MWe of continuous power, with Stellaria emphasizing both the potential for 24/7 firm output and the ability to consume certain categories of nuclear waste as fuel. For hyperscale data center operators, that combination of baseload power, carbon-free generation and reduced on-site waste storage is particularly attractive.
Equinix, headquartered in California, operates more than 270 data centers in 77 metropolitan areas globally. In Europe, the company already reports 100% renewable coverage for its operations and has been an active buyer of long-term renewable power purchase agreements, including in France. Advanced nuclear is being positioned not as a replacement for renewables, but as a complementary, dispatchable power source that can support the extreme, often spiky loads associated with AI training clusters and GPU-rich infrastructure.
For Stellaria, the Equinix agreement is an important commercial signal in a market where most advanced reactor projects are still at the design and licensing stage. CEO Nicolas Breyton described the deal as a turning point that validates Stellaria’s strategy and provides a clear demand signal ahead of planned Stellarium deployments beginning in 2035, subject to regulatory approvals and industrialization.
The concept of using molten salt reactors (MSRs) for data center power is still highly speculative, but technically compelling. MSRs use molten fluoride or chloride salts as both coolant and, in some designs, as a carrier for dissolved nuclear fuel. Operating at low pressure but high temperature, they promise inherent safety features, high thermal efficiency and the ability to run on alternative fuel cycles, including thorium-based systems that breed fissile uranium-233. They can be configured for fast or epithermal neutron spectra, opening options for burning transuranic waste or optimizing for different fuel strategies.
Nuclear Safety Regulations
However, the path to commercialization remains complex. MSR designs must navigate stringent nuclear safety regulations, materials challenges such as corrosion in hot salt environments, fuel cycle logistics and public acceptance. Several design variants exist, and standardization is still limited. Stellaria will need to demonstrate not just technical feasibility, but also bankability, manufacturability at scale and competitive levelized cost of electricity.
From a digital infrastructure standpoint, the Equinix–Stellaria agreement underscores how rapidly the power profile of AI-era data centers is changing. As rack densities climb, workloads become more continuous and AI training clusters behave more like industrial loads than traditional IT, operators are exploring options far beyond incremental efficiency gains and grid contracts. Co-locating or closely siting advanced nuclear capacity could, if realized, offer latency-free, predictable power, reduce exposure to grid constraints and potentially stabilize long-term energy costs.
The deal does not mean that Equinix data centers will be running on molten salt nuclear power in the near term; 2035 is a long horizon in both technology and policy terms. But for B2B technology and infrastructure leaders, it is another sign that the convergence of AI, energy transition and digital sovereignty is pushing hyperscalers and colocation providers to experiment with unconventional energy partnerships.
If Stellaria’s roadmap holds, the first Stellarium units would come online at a time when both AI workloads and grid decarbonization pressures are expected to be far higher than today. Whether this specific design succeeds or not, the Equinix pre-order signals that major data center operators are willing to act as early offtakers for next-generation nuclear, provided it can deliver the dual promise of carbon-free baseload power and robust safety.
Executive Insights FAQ
What exactly did Equinix agree to with Stellaria?
Equinix has signed a pre-order capacity reservation with Stellaria, securing access to power from the first planned Stellarium molten salt reactor. It is a forward-looking commitment rather than an immediate power contract, linked to reactors Stellaria aims to deploy from 2035 onward.
Why are data center operators looking at molten salt reactors?
AI and high-density workloads are driving up continuous power demand and tightening resilience requirements. Molten salt reactors promise 24/7 baseload, low-carbon electricity in a compact footprint, potentially located near or alongside large data center campuses, which is attractive for operators seeking both energy security and decarbonization.
How does this fit with Equinix’s existing renewable strategy?
Equinix already sources 100% renewable electricity in Europe and invests heavily in renewable PPAs. Advanced nuclear is being explored as a complementary, firm power source that can backstop intermittent renewables and support extremely power-hungry AI clusters where uptime and predictability are critical.
What is unique about Stellaria’s Stellarium reactor concept?
Stellarium is a very compact molten salt reactor design that uses liquid nuclear fuel and is intended to operate on multiple fuel types, including some waste streams such as minor actinides. Stellaria claims the design can consume more nuclear waste than it generates, combining power production with waste reduction, although this remains to be demonstrated commercially.
When could Equinix realistically use power from a Stellarium reactor?
Stellaria currently targets 2035 for the first Stellarium deployment, contingent on successful development, licensing and financing. Any Equinix data center powered by such a reactor would therefore be at least a decade away, making this agreement primarily a strategic signal rather than an immediate change in Equinix’s energy mix.
