In the winter of 2022 energy prices surged across Europe, lights dimmed, factories slowed, and governments scrambled for options. It was a wake-up call: we still rely
on fragile, centralised energy systems vulnerable to geopolitics and supply shocks. What if the answer wasn’t more fossil fuels, but a smarter, safer kind of nuclear that could run on yesterday’s waste and tomorrow’s abundant materials?
It wouldn’t be the first time such a solution was within reach. Back in the 1960s, a small team at Oak Ridge National Laboratory in the US successfully ran a Molten Salt Reactor (MSR). It was stable, self-regulating, and efficient – a quiet revolution in nuclear design. But the project was put aside, buried under the politics and priorities of its time. Now, as climate urgency mounts and energy security becomes critical, molten salt technology is getting a second look.
Molten salt reactors
Molten Salt Reactors are Generation IV designs that use molten salt as both fuel and coolant. In these systems, nuclear fuel is dissolved in a high-temperature, low-pressure liquid salt mixture.
Unlike traditional reactors that rely on fixed fuel rods and leave behind long-lived and high activity waste, molten salt reactors can run on a much broader mix of fuels. That includes some of the hardest to manage nuclear materials like spent fuel along with materials that have barely been tapped, like depleted uranium and thorium.
The design has built-in safety features. Because the system runs at low pressure, it reduces the risk of explosive failures. Also, since the salt in the system is a liquid, it expands with rising temperature, which naturally slows down the fission reaction without needing human intervention. Add in the ability to eliminate long-lived waste and run more efficiently than conventional reactors, you have a technology with real potential.
While molten salt reactors have long been admired for their potential, building one that could survive real-world conditions and meet modern safety standards has been difficult primarily due to two challenges:
- Material Integrity: The parts of a reactor that come into contact with molten salt face extreme heat, corrosive conditions, and constant radiation. Designing materials that can last for 60+ years under such stress has proven extremely difficult.
- Fuel Management: Molten salt reactors need large amounts of liquid fuel, and figuring out how to safely move, store, and handle that salt, especially once it’s been used, hasn’t been easy.
These were the issues that previously kept molten salt reactors a scientific curiosity rather than a commercial reality.
The Cartridge-based core
Thorizon has taken a fresh approach to an old problem, starting with a rethink of the reactor core. Instead of one massive structure with permanent fuel chambers, Thorizon’s patented design uses a series of sealed, modular cartridges filled with molten salt fuel. These cartridges power the reactor and are replaceable every five to 10 years. They operate in unison to maintain criticality. Each cartridge is sealed, transportable, and contains its own pump and heat exchanger. Given that all the complexity stays inside the cartridge, it makes it possible to manufacture these systems off-site, simplifying on-site construction and enabling true modular deployment.
Together, these features enable walk-away safety, straightforward fuel handling, and practical licensing – all crucial for commercial viability. This design is the foundation for Thorizon’s first commercial system.
During operation, the pump moves the salt upwards through the cartridges. Criticality occurs only when all cartridges are active and salt is circulating. Fission occurs through neutron interaction at the top of the reactor. The heat then flows to the bottom and is extracted through the heat exchanger. At the end of the cartridge lifecycle, or in case of a power failure, the pump stops and the salt drops to the bottom of the cartridges. This stops the fission reaction automatically. This way, the reactor stays safe, even during a full power outage scenario.
The Thorizon One is designed to deliver 250 MW of industrial heat, which can be directly used in sectors like the chemical industry or hydrogen production. This heat can also be transformed into 100 MW of electricity. The reactor is also designed to provide flexible capacity of between 50 MW and 300 MW, storing energy when demand is low and releasing it during peak hours.
The road to commercialisation
Thorizon hasn’t built this vision in isolation. Since its inception, Thorizon has assembled a strong ecosystem of public and private partners. The Thorizon One has been endorsed as the only molten salt reactor project in the EU Small Modular Reactor (SMR) Industrial Alliance – a significant recognition of its strategic relevance to Europe’s energy future.
Thorizon was awarded a €10m grant in 2024 as part of a consortium with Orano through the France 2030 programme, making it one of only three molten salt reactor projects selected. Together with Orano, Thorizon is leading 10 specialised work packages, ranging from fast spectrum reactor design and cartridge handling to fuel salt transport and nuclear safety awareness, with strong involvement from CEA, NRG, and other top-tier research institutions.
In parallel, Thorizon has teamed up with VDL and Demcon to demonstrate the manufacturability and functionality of key molten salt reactor components. This long-term collaboration will support critical prototyping, including heat exchanger development and salt purification systems.
Most recently, in March 2025, Thorizon announced a successful fundraising of €20m to accelerate reactor development. This includes a €16m equity commitment from existing investors led by Invest-NL, and a €4 million grant from the Province of Noord-Brabant. This new capital will support licensing efforts, engineering development, and partnership building. Thorizon is actively seeking strategic industrial collaborators and investors across Europe to support cross-border deployment and scale-up.
A full construction licence application is planned for 2027, with the aim of beginning construction of Thorizon One by 2030.
Looking ahead
Thorizon was started as a small team and the belief that molten salt reactors could finally deliver on their early promise – if approached differently. Today, that belief is stronger than ever. Thorizon’s team has grown, its technology has matured, and the momentum behind clean, flexible nuclear energy is undeniable.
From the outset, Thorizon has focused on bringing a practical, real-world mindset to a field too often stuck in theory. As Europe faces rising energy demand, geopolitical volatility, and the urgent need to decarbonise, the need for practical solutions has never been greater. The energy space requires technologies that are ready to be built, scaled, and trusted. Molten salt is among the most promising.
