Stellaria, a French startup focused on next-generation nuclear technology, has raised €23 million in a new funding round to further develop its fast neutron molten-salt reactor. This marks the company’s second successful fundraising effort since its founding in 2023.
The round was co-led by U.S.-based impact fund At One Ventures and France’s Supernova Invest, with continued support from Stellaria’s early backers: CEA Investissements, Schneider Electric, Technip Energies, and Exergon.
Stellaria’s total funding includes €10 million in non-dilutive public support through France 2030’s “Innovative Reactors” program. The startup plans to use this capital to carry out technical and regulatory studies ahead of a demonstration reactor capable of sustaining fission by 2029. A commercial rollout is targeted for 2035.
This new phase also positions the company to file an Application for Authorisation to Create (DAC) a Basic Nuclear Installation (INB) in the coming months.
Stellaria operates in a field undergoing renewed interest, as governments and industries look for low-carbon energy alternatives that are scalable, safe, and reliable. Its reactor, the Stellarium, offers a different approach: it uses liquid fuel and fast neutrons to regenerate its own fuel, potentially reducing nuclear waste.
"The reactor offers low CAPEX and LCOE, passive safety with 72-hour cooldown, fuel flexibility, and fast power ramping," said Laurie Menoud, Partner at At One Ventures. "This is the kind of planetary impact we’re here for—clean, dispatchable power that can be built faster, sited closer, and operated more safely.”
Supernova Invest’s François Breniaux emphasized the importance of Stellaria’s technology for heavy industries. “Stellaria offers the only viable solution for many industries requiring a high-power energy supply, long-term price stability, and the operational flexibility of gas-fired power plants.”
The new capital will enable Stellaria to double its team and accelerate research and development. A key milestone will be the construction of a liquid-core, fast-neutron demonstrator at its research site in Grenoble.
The company also aims to invest several million euros to expand its laboratory facilities and deepen scientific collaborations. Preparing for regulatory approval is another major focus area, as it looks to obtain clearance for the prototype reactor.
Founded in 2023 by a team spun out of CEA and Schneider Electric, Stellaria is building a fourth-generation reactor called the Stellarium. Designed for long-term autonomy, the reactor can operate for over 20 years without refueling and actively reduces long-lived nuclear waste by destroying minor actinides.
Stellaria’s CEO, Nicolas Breyton, said, “We are laying the foundations for a model in which electro-intensive industries become self-sufficient in energy throughout the lifetime of their facilities.”
By replacing fossil fuels with the Stellarium, the company claims it can reduce CO₂ and particulate emissions from industrial sites by up to 99%.
In addition to lead investors, Stellaria continues to receive support from Schneider Electric, Technip Energies, and CEA Investissements. Each brings sector expertise and strategic backing that strengthens Stellaria’s industrial roadmap.
“We will support Stellaria in the industrial scale-up of this controllable, low-carbon energy production technology through concrete projects,” said Benjamin Lechuga, Chief Strategy and Sustainability Officer at Technip Energies.
Giuseppe Sangiovanni, Co-founder of Exergon, added: “We are delighted with the company’s continuing progress and the milestones already validated. This is a project with growing prospects across Europe and globally.”
The fundraising process was advised by Yards and Optiva Capital, while investor-side legal counsel was provided by Chammas & Marcheteau and Goodwin.
