Marie Dubois still remembers the day her family’s century-old glass factory nearly shut down. Rising gas prices had pushed their heating costs through the roof, and competitors using cheaper energy were undercutting their prices. “We were looking at laying off half our workforce,” she recalls, staring at the massive furnaces that had kept her grandfather’s business alive for decades. “Then someone mentioned these new mini nuclear reactors that could replace our gas boilers.”
That conversation happened two years ago. Today, Marie’s story might have a very different ending, as France takes its first serious steps toward making mini nuclear reactors a commercial reality.
The French nuclear industry has always been about thinking big – massive concrete domes, gigawatt-scale power plants, and projects that take decades to complete. But a quiet revolution is brewing in research labs and startup offices across the country, where engineers are betting on something radically different: nuclear reactors small enough to fit in a factory courtyard.
Two Companies Are Now Racing to Build France’s First Mini Reactors
On January 22, French startup Stellaria made headlines by filing the country’s second formal application to build a mini nuclear reactor. The company submitted its “demande d’autorisation de création” to the Autorité de sûreté nucléaire (ASN), France’s nuclear safety watchdog.
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This follows a similar application from Jimmy, another French startup focused on industrial heating, which broke new ground in early 2024 by becoming the first company to seek regulatory approval for a small nuclear unit in France.
“We’re witnessing a fundamental shift in how France thinks about nuclear energy,” explains Dr. Pierre Laurent, a nuclear engineering consultant who has worked with both traditional and small reactor projects. “Instead of building massive plants to power cities, these companies want to put nuclear reactors right where the heat is needed – in factories, chemical plants, and industrial facilities.”
Stellaria’s application covers their prototype called Stellarium, an “advanced modular reactor” designed to work as an industrial boiler rather than a traditional power plant. The company wants to target facilities that currently burn gas and coal to generate process heat – exactly the kind of applications that could help Marie’s glass factory stay competitive.
What Makes These Mini Nuclear Reactors Different
These aren’t just scaled-down versions of France’s existing nuclear plants. The technology behind mini nuclear reactors represents a completely different approach to nuclear energy, built around several key advantages:
- Size and modularity: Small enough to be factory-built and transported by truck
- Faster deployment: Months instead of decades for installation
- Lower upfront costs: Millions rather than billions in initial investment
- Industrial focus: Designed for process heat rather than electricity generation
- Advanced safety systems: Built-in passive safety features that don’t rely on external power
Stellaria emerged from the French Alternative Energies and Atomic Energy Commission (CEA) at Paris-Saclay in 2022. The startup keeps its team lean but highly specialized, drawing on decades of research into Generation IV reactor designs that had been sitting in laboratories waiting for commercial application.
“The breakthrough isn’t just technical – it’s economic,” notes Dr. Sophie Chen, an energy policy researcher at Sciences Po. “These reactors could finally make nuclear competitive for industrial heat applications that have been dominated by fossil fuels.”
| Feature | Traditional Nuclear Plant | Mini Nuclear Reactor |
|---|---|---|
| Power Output | 1,000-1,600 MW | 1-50 MW |
| Construction Time | 10-20 years | 2-3 years |
| Initial Cost | €10-20 billion | €50-200 million |
| Primary Use | Electricity generation | Industrial process heat |
| Site Requirements | Massive dedicated facility | Existing industrial sites |
How Stellarium’s Molten Salt Technology Works
Stellarium doesn’t use the pressurized water reactor design that dominates French nuclear plants. Instead, it relies on molten salt and fast neutrons – a Generation IV approach that offers several technical advantages.
The molten salt acts as both coolant and fuel carrier, eliminating the need for solid fuel rods that can overheat. This design operates at atmospheric pressure, reducing the risk of explosive accidents that have plagued traditional reactors.
“The molten salt approach is inherently safer because if something goes wrong, the fuel naturally drains into a safe configuration,” explains Dr. Laurent. “You don’t need complex emergency systems – the physics of the reactor works in your favor.”
The reactor can also consume nuclear waste as fuel, potentially addressing one of the industry’s biggest challenges. This feature could be particularly attractive in France, which has been storing nuclear waste for decades while debating long-term disposal solutions.
Who Could Benefit from Mini Nuclear Reactors
The target market for these mini nuclear reactors isn’t residential neighborhoods or small towns. Instead, companies like Stellaria are focusing on industrial facilities that consume enormous amounts of process heat:
- Glass manufacturing: Furnaces that need constant high-temperature heat
- Steel production: Mills requiring steady thermal energy for processing
- Chemical plants: Facilities using heat for refining and synthesis
- Food processing: Large-scale operations needing steam and hot water
- Paper mills: Plants using heat for pulping and drying processes
These industries currently depend heavily on natural gas and coal, making them vulnerable to price spikes and environmental regulations. A mini nuclear reactor could provide decades of stable, carbon-free heat at predictable costs.
“For industrial customers, energy security is just as important as cost,” notes Dr. Chen. “A nuclear reactor on-site means you’re not dependent on gas pipelines from Russia or coal shipments that can be disrupted by global events.”
The Regulatory Challenge Ahead
Filing an application with ASN is just the beginning of a complex approval process. The French nuclear safety authority will spend months or potentially years evaluating Stellaria’s design, safety systems, and operational procedures.
The regulatory framework for mini nuclear reactors is still evolving. ASN must adapt rules written for gigawatt-scale plants to much smaller, modular designs that could be deployed across multiple industrial sites.
“The regulator faces a unique challenge,” explains nuclear industry analyst Jean-Marc Rousseau. “They need to ensure safety without stifling innovation, and create a pathway that makes sense for smaller companies that don’t have EDF’s resources.”
Success stories from other countries could influence France’s approach. The United States has already licensed several small reactor designs, while Canada and the UK are developing their own regulatory frameworks for mini nuclear reactors.
If approved, Stellaria’s reactor could begin commercial operations within five to seven years. That timeline would make France one of the first European countries to deploy Generation IV nuclear technology at commercial scale.
For Marie Dubois and thousands of other industrial facility owners across France, that timeline can’t come soon enough. Rising energy costs and pressure to reduce carbon emissions are forcing difficult decisions about the future of energy-intensive industries.
“We’re not just talking about saving individual businesses,” she reflects. “This technology could keep entire industrial sectors competitive in France while helping us meet our climate goals.”
FAQs
What exactly is a mini nuclear reactor?
A mini nuclear reactor is a small-scale nuclear power plant designed to generate 1-50 MW of power, compared to 1,000+ MW for traditional plants. They’re built for industrial process heat rather than large-scale electricity generation.
How safe are these smaller reactors compared to traditional nuclear plants?
Mini nuclear reactors often incorporate passive safety systems that work without external power, and many designs like Stellarium’s molten salt reactor are inherently safer due to their physics and operating conditions.
How much would a mini nuclear reactor cost for a business?
Initial estimates suggest costs between €50-200 million depending on size and complexity, which is significantly less than billions required for traditional nuclear plants.
When could the first mini nuclear reactor start operating in France?
If regulatory approval goes smoothly, the first commercial mini nuclear reactor could begin operations in France within 5-7 years.
What industries would benefit most from mini nuclear reactors?
Glass manufacturing, steel production, chemical plants, large food processing facilities, and paper mills – basically any industry requiring constant high-temperature process heat.
Could mini nuclear reactors replace fossil fuels in French industry?
They have the potential to replace gas and coal for process heating in many industrial applications, which could significantly reduce France’s industrial carbon emissions while improving energy security.