Jan 28, 2026
Stellaria requests approval to construct an experimental reactor.
French molten salt reactor developer Stellaria has announced its intention to obtain the required approvals to build an experimental reactor. The application is currently under review.
The start-up, which originated from the French Alternative Energies & Atomic Energy Commission and Schneider Electric, submitted its creation authorization decree (DAC) for its Basic Nuclear Installation (INB) Alpha to the French nuclear safety minister on December 19.
The application pertains to the siting and construction of its 100 kW Alvin experimental reactor, planned to become operational in 2030, to initiate a test program that will conclusively validate the concept.
The submission includes approximately 15 documents totaling over 1,000 pages. It encompasses the safety case, detailing the installation, adopted safety principles, incident and accident analyses (including severe accidents), management of external hazards (such as earthquakes, flooding, aircraft crashes), and radiation safety for workers, the public, and the environment. Additionally, it contains the environmental impact assessment, planned decommissioning conditions, a presentation of the operator’s technical and financial preparedness, and comprehensive technical documentation essential for the application review.
"This new milestone is a critical advancement for Stellaria in the development and implementation of its Stellarium reactor, outlining the primary principles of the project and officially recognizing the start-up as a nuclear operator," Stellaria stated. "To date, Stellaria is the first company to file such an application in the French fast-neutron nuclear market and the second among the eleven French start-ups focused on developing SMRs or AMRs, following Jimmy Energy."
The Stellarium reactor proposed by Stellaria is highly compact (4 cubic meters) and can utilize a diverse range of nuclear fuels (including uranium, plutonium, mixed-oxide, minor actinides, and even thorium). Stellaria claims it is "the world's first reactor to operate with a liquid fuel capable of destroying more waste than it generates."
After the Alvin reactor validates Stellaria's concept, the company intends to construct a 10 MWe prototype reactor named MegAlvin.
"2025 was a critical year for Stellaria," stated Nicolas Breyton, President of Stellaria. "Following a structured fundraising round and the signing of a preliminary power order agreement with Equinix, a global leader in data centers, the submission of the DAC signifies reaching a new milestone. This step is crucial for Stellaria, as it affirms the work done by its teams and partners to date and fully engages the company in its responsibilities as a nuclear operator. By filing this application, Stellaria progresses beyond the concept phase into a structured regulatory stage with foundational decisions now established."
Molten salt reactors (MSRs) utilize molten fluoride salts as primary coolant at low pressure. They can operate with epithermal or fast neutron spectra and diverse fuels. Current interest in reviving the MSR concept largely revolves around using thorium to breed fissile uranium-233, necessitating an initial fissile material source such as plutonium-239. Various MSR design concepts exist, each presenting unique challenges for commercialization, especially concerning thorium.
The start-up, which originated from the French Alternative Energies & Atomic Energy Commission and Schneider Electric, submitted its creation authorization decree (DAC) for its Basic Nuclear Installation (INB) Alpha to the French nuclear safety minister on December 19.
The application pertains to the siting and construction of its 100 kW Alvin experimental reactor, planned to become operational in 2030, to initiate a test program that will conclusively validate the concept.
The submission includes approximately 15 documents totaling over 1,000 pages. It encompasses the safety case, detailing the installation, adopted safety principles, incident and accident analyses (including severe accidents), management of external hazards (such as earthquakes, flooding, aircraft crashes), and radiation safety for workers, the public, and the environment. Additionally, it contains the environmental impact assessment, planned decommissioning conditions, a presentation of the operator’s technical and financial preparedness, and comprehensive technical documentation essential for the application review.
"This new milestone is a critical advancement for Stellaria in the development and implementation of its Stellarium reactor, outlining the primary principles of the project and officially recognizing the start-up as a nuclear operator," Stellaria stated. "To date, Stellaria is the first company to file such an application in the French fast-neutron nuclear market and the second among the eleven French start-ups focused on developing SMRs or AMRs, following Jimmy Energy."
The Stellarium reactor proposed by Stellaria is highly compact (4 cubic meters) and can utilize a diverse range of nuclear fuels (including uranium, plutonium, mixed-oxide, minor actinides, and even thorium). Stellaria claims it is "the world's first reactor to operate with a liquid fuel capable of destroying more waste than it generates."
After the Alvin reactor validates Stellaria's concept, the company intends to construct a 10 MWe prototype reactor named MegAlvin.
"2025 was a critical year for Stellaria," stated Nicolas Breyton, President of Stellaria. "Following a structured fundraising round and the signing of a preliminary power order agreement with Equinix, a global leader in data centers, the submission of the DAC signifies reaching a new milestone. This step is crucial for Stellaria, as it affirms the work done by its teams and partners to date and fully engages the company in its responsibilities as a nuclear operator. By filing this application, Stellaria progresses beyond the concept phase into a structured regulatory stage with foundational decisions now established."
Molten salt reactors (MSRs) utilize molten fluoride salts as primary coolant at low pressure. They can operate with epithermal or fast neutron spectra and diverse fuels. Current interest in reviving the MSR concept largely revolves around using thorium to breed fissile uranium-233, necessitating an initial fissile material source such as plutonium-239. Various MSR design concepts exist, each presenting unique challenges for commercialization, especially concerning thorium.