Stellaria signs CEA deal to study Alvin molten-salt reactor at Cadarache

Stellaria’s push into Cadarache is less a branding exercise than a credibility test. On April 23, the molten-salt developer and France’s Alternative Energies and Atomic Energy Commission signed a letter of intent to study an Alpha basic nuclear installation at CEA Cadarache in Saint-Paul-lez-Durance, a campus that already anchors major work in fission, fusion, bioenergy and solar energy, alongside ITER.

That matters because Stellaria is not just sketching a reactor on paper anymore. The company filed its creation authorization application for Alpha on December 19, 2025, and said in January 2026 that it had become a nuclear operator. The Cadarache study now asks the next hard question: can Stellaria place a first-of-kind experimental machine inside one of Europe’s most demanding nuclear environments and clear the technical, licensing and siting hurdles that turn concept into buildable hardware?

The proposed Alpha INB would house a test model, a fast-spectrum liquid-fuel molten-salt demonstration reactor and a salt fabrication facility. Stellaria says Alvin, the first experimental reactor in the sequence, is a 100 kW unit scheduled to start up in 2030. By 2032, the company wants to modify the facility for MegAlvin, a 10 MWe prototype. Its commercial design, Stellarium, is targeted for 2035.

For Europe’s advanced-reactor crowd, the CEA tie-up is significant because access to Cadarache signals proximity to the sort of engineering culture that can pressure-test claims about materials, safety case development and manufacturability. A letter of intent does not create a reactor, but it can open the door to site studies, regulator-facing work and a more disciplined deployment path. That is the kind of de-risking investors and industrial partners look for before they treat a first-of-a-kind system as more than a long-duration bet.

Stellaria’s pitch is ambitious. The company says its liquid core can ramp from 0% to 100% output in about three minutes, and it and CEA say pairs of reactors on roughly four hectares could deliver up to 1,000 MW of heat or 500 MW of power. In practice, that promise still has to survive authorization, engineering detail and the realities of nuclear construction. But the company has been building a funding trail to match the timeline, raising €2 million in 2023, securing €10 million in government support in 2024 and collecting a total of €23 million in July 2025.

The CEA deal also gives Stellaria a stronger European storyline. The company says it originated from CEA and Schneider Electric, counts five founders including three CEA employees, and has already drawn industrial interest from Schneider Electric, Technip and Orano. Equinix went a step further in November 2025, securing the first power-capacity reservation on Stellarium. If Cadarache turns from study to site, Stellaria will have moved one step closer to proving that molten-salt commercialization in Europe can be licensed, financed and eventually built.