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Copenhagen Atomics has successfully completed two years of continuous operation of a molten salt pump and test loop at its facilities in Copenhagen.
The system has been running without issues under high-temperature molten salt conditions, marking one of the longest continuous durability tests of its kind worldwide.
The milestone represents a significant validation of critical components required for molten salt reactors and is an important step in Copenhagen Atomics’ ambition to become a leading supplier of next-generation molten salt reactor technology.
Professor Emeritus Niels J. Bjerrum*:
This is exactly the kind of milestone molten salt technology needs. For decades, molten salt reactors have been discussed as a promising next-generation nuclear solution, but progress depends on proving that key components can operate reliably over years, not weeks. Demonstrating continuous pump operation under realistic molten salt conditions for two full years is a major technical validation and an important step toward commercial and regulatory readiness.
About Niels J. Bjerrum:
Niels J. Bjerrum is a Danish chemist with expertise in molten-salt and high-temperature chemistry. While he conducted research at Oak Ridge National Laboratory in the 1960’s, he was not involved in the thorium molten salt reactor experiments themselves.
Molten salt reactors rely on pumps to circulate liquid fuel or coolant at temperatures exceeding 600 °C for years at a time. Demonstrating long-term, stable pump operation is therefore a prerequisite for regulatory approval and commercial deployment.
Thomas Jam Pedersen, CEO and Co-Founder of Copenhagen Atomics, says:
Component reliability is not something you prove once, it has to be proven repeatedly over long periods and under realistic conditions. Running a molten salt pump continuously for two years is a major technical milestone, and it confirms that our approach to design, materials, salt purity and testing works as intended.
A test platform built for scale and realism
The pump is part of Copenhagen Atomics’ pumped molten salt loop platform, a fully integrated test system designed to replicate the thermal, chemical and mechanical conditions found in future reactors, but without nuclear fission. Across the company’s test infrastructure, Copenhagen Atomics has now accumulated more than 100,000 hours of combined pump runtime, and many pumps have exceeded one year of runtime.
Unlike many reactor developers, Copenhagen Atomics designs and builds its pumps, control electronics, sensors and test loops in-house, and produces highly purified molten salts at tonne scale. This vertically integrated approach allows the company to run long-duration tests at a fraction of the cost typically seen at national laboratories or large research facilities.
Thomas Jam Pedersen says:
For regulators data matters. Not optimism or simulations, long-duration component testing dramatically reduces risk later in the development process. Finding and fixing issues in a test loop is orders of magnitude cheaper than discovering them in a prototype reactor.
Why long-duration testing matters
While molten salt reactors have been studied for decades, the global industry has accumulated very limited operational experience. Fewer than a handful of molten salt reactors have ever operated, and for only short periods. This lack of historical data increases regulatory requirements for component testing.
Copenhagen Atomics’ strategy is therefore to push as much learning as possible into non-fission test systems. By operating multiple molten salt loops in parallel, the company can accumulate operating hours, iterate designs, and generate statistically meaningful reliability data for pumps, valves, heat exchangers and sensors.
The two-year continuous run demonstrates that molten salt pumps can operate stably over timescales relevant to future commercial reactors, which is a key hurdle for the technology as a whole.
A competitive advantage in molten salt reactors
Extensive testing requires infrastructure, know-how and sustained investment. Copenhagen Atomics began building molten salt systems more than ten years ago and has since developed more than ten generations of test loops.
This experience now represents a competitive advantage as interest in molten salt reactors accelerates globally.
Thomas Jam Pedersen says:
Many companies talk about commercial reactors, what matters is whether the underlying components have been tested long enough to satisfy regulators and customers. This milestone shows that we are steadily turning molten salt reactors from a promising concept into an engineered, licensable technology.
Copenhagen Atomics plans to continue expanding its test capacity over the coming years, with the long-term goal of operating dozens of molten salt loops in parallel, both in Copenhagen and with partner institutions.