Stellaria and the CEA announce the signing of a Letter of Intent (LOI) regarding the feasibility study for the establishment of an “ ALPHA ” INB housing a test model, a fast-spectrum liquid-fuel (molten salt) demonstration reactor, and a salt fabrication facility to supply the prototype and demonstration reactor at the CEA’s Cadarache site. To this end, a site has been identified to study the feasibility of establishing the ALPHA INB at the CEA ’s Cadarache site.
This is an important new milestone for Stellaria, as the signing of this letter of intent lays the foundations for Alvin, our critical experiment, scheduled for 2030 through the INB Alpha facility. The objectives to be achieved with Alvin are multiple, but it will notably allow us to validate our neutronics-thermohydraulic coupling modelling and calculations.
A letter intent for what?
The letter of intent concerns INB Alpha, which encompasses both Alvin and MegAlvin. Indeed, by 2032, following the completion of our Alvin experimental programme, we plan to modify the facility to operate MegAlvin, our prototype reactor.
It will be installed within the building used for the Alvin critical experiment, the main modification consisting of replacing certain systems as well as the vessel, with a larger one (approximately 40 to 100 cm).
MegAlvin objectives:
- Conducting endurance and qualification tests on fuel
- Testing structural materials and systems specific to molten salt reactors
- Obtaining sufficient operational feedback, available several years before the commissioning of our first commercial reactor, the Stellarium, in 2035.
MegAlvin in the service of science
Long-duration irradiation of test specimens will enable the qualification of the mechanical properties of various materials under fast neutrons. This capability will be unique in Europe and available to other stakeholders (startups or national programmes). MegAlvin will notably provide data on fuel qualification and its evolution under irradiation, as well as the validation of our design of systems critical to the development of molten salt reactors, such as corrosion management and fission gas handling.
Key milestones reached alongside the signing of the letter of intent
- The Preliminary Design Study (Avant-Projet Sommaire) for Alvin was finalised in late 2025
- On the regulatory front, exchanges with the ASNR are well underway: the construction authorisation request (DAC) for the facility was submitted in late 2025
- In the meantime, a funding round of €23M was closed. This raise will complement the €10 million in non-dilutive funding obtained by Stellaria as a laureate of the "Innovative Reactors" call for projects under the France 2030 plan, and will finance all the technical and regulatory studies required to establish the world's first molten salt facility capable of achieving a fission reaction, expected from the 2030s onwards.
- That same year, Stellaria signed a commercial contract with its firts customerEquinix. This pre-order agreement will allow Equinix data centres to benefit from the energy autonomy of the world's very first nuclear reactor with renewable fuel, enabling sustainable, low-carbon artificial intelligence capabilities.
Why sign a Letter of Intent with the CEA?
The CEA, a public research organisation, plays a key role in nuclear innovation — notably by supporting the French industrial sector, major research programmes, and more recently by accompanying France 2030 laureate projects through their development and industrialisation. The CEA's Cadarache centre, located in Saint-Paul-Lez-Durance (Bouches-du-Rhône), is dedicated to research platforms and technological development in low-carbon energies (fission nuclear, fusion nuclear, solar, bioenergies, biotechnologies, hydrogen).