Jun 23, 2025 · 1 hr 7 min
Copenhagen Atomics is an ambitious Danish company with a bold, potentially world-changing vision. They’re driven by a goal of manufacturing one reactor per day from a high quality, certified factory. If they achieve that goal, they would be adding an additional 37 GW/year of heat to the global energy supply. They want to help make affordable, reliable, clean and abundant energy available to everyone on the planet.
Thomas Jam Pedersen is a co-founder and the CEO of Copenhagen Atomics. He recently visited the Atomic Show to describe his company, its history, its vision and its technology. He provided a wealth of information during a lengthy conversation and also shared a brief about the company, its facilities, its potential markets and the physical fabrication and testing units.
The company was founded by a group of four Danish engineers and businessmen with a complimentary set of valuable skills and experience. They were each “bitten by the thorium bug” through individual research starting in the late 2000s. They came to the decision to start a company about ten years ago through a series of meetings at Copenhagen bars and restaurants.
Copenhagen Atomics is developing a molten salt reactor that uses a kickstarter actinide fuel (U-233, U-235 or Pu-239) along with a thorium blanket and heavy water moderator to produce 100 MW of heat. The nuclear heat source system – including pumps, tanks, pipes, valves and the proprietary “onion core” reactor – fits into a standard shipping container. After 5 years of operation, the molten salt contains almost as much fissile material as it did when it was initially loaded into the fuel.
In the future, the fissile material inventory at the end of 5 years will be equal to, or slightly greater than it was at the beginning. The Waste Burner reactor will eventually become a thermal spectrum breeder reactor that adds to the world’s fissile material inventory.
The container and its included systems would be fully manufactured and tested at the factory, but it would be shipped to its destination with no loaded fuel using conventional shipping methods. The destination facility could use heat for a conventional steam power plant or it could use the heat for an application like manufacturing fertilizer or desalinating water.
In the current business model, the receiving facility would be erected by a customer that had contracted to purchase heat coming from the pre-fabricated reactor furnished by Copenhagen Atomics. The power plant design and construction would include a series of shielded “cocoons”, each with two meter thick walls and enough internal space for the container and a number of tanks and connections.
Each reactor would be inserted into a cocoon, loaded with fuel from tanks in the cocoon and connected to the receiving heat system using welded connections. The welding would be done by an automated system that is already under development and testing at Copenhagen Atomics’s 9,000 m² fabrication and testing facility in Copenhagen. (See photos in the company presentation.)
The containers and their included mechanical systems are fabricated out of conventional stainless steel and designed to be affordably replaced every five years. At the end of this operating life, they would be defueled and replaced with the fuel salt put into the new reactor. The old reactor would be stacked into a pre-existing storage facility at the power plant where it would remain for several decades to allow radioactive isotopes to decay.
After the containers have sufficiently cooled – from a radioactivity perspective – they could be recycled into materials for new reactors or compacted for storage at low level waste facilities.
Though Denmark does not allow the government to invest in nuclear power facilities, it has a respected regulator with many decades worth of experience in regulating radioactive materials and nuclear research facilities that include reactors. But Copenhagen Atomics’s current development path includes construction of an initial fissioning test reactor at the Paul Scherrer Institute in Switzerland. That facility is currently planned to be completed in 2028, but that date can vary depending on a number of factors, including the time required to arrange appropriate financing.
Copenhagen Atomics is a company founded by practical engineers that know that real products require a vast amount of physical testing. They build parts – including tanks, pipes, valves, sensors and pumps – and assemble them into both partial and complete systems that allow them to test materials and performance at operating conditions. They started with non radioactive salts and are progressing to tests and demonstrations using non-fissile actinides and then to the actual fuel materials that will be used in commercial facilities.
So far, the company has accumulated 100,000 hours of actual system testing. They have developed refined test loops that are good enough to have been sold to other researchers working on molten salts. They have developed large scale salt production systems and gradually increased their production rates.
If all continues to progress, Copenhagen Atomics expects that its first commercial reactor unit will be operating in about 5 years. But Thomas Jam is a practical and patient man who realizes that there are lot of obstacles left to overcome.
Disclosure – Nucleation Capital is an investor in Copenhagen Atomics. We believe that the company’s vision is important, visionary and potentially valuable. We appreciate the iterative approach to design and manufacture; it is vital for teams designing something new to build, test, redesign and rebuilt as often as needed to produce refined products.
We think you will appreciate the opportunity to learn more about Copenhagen Atomics in a discussion that delves into some deeply technical issues.
