SMRS & ADVANCED REACTORS | PROVING RELIABILITY
Proving MSR reliability
Copenhagen Atomics’ recent durability milestones and corrosion breakthroughs are key to advancing molten salt reactors from concept to industrial reality. CEO and co-founder, Thomas Jam Pedersen talks to NEI about the road less travelled.
WIDELY REGARDED AS ONE OF the more promising of the next-generation small modular reactor technologies, molten salt reactors (MSRs) have nonetheless been persistently constrained by unresolved materials challenges. Two recent developments from Copenhagen Atomics aim to bridge that credibility gap by demonstrating the long-term performance of systems and materials. The results point to both technical feasibility and a broader strategy centred on reliability, cost reduction and industrial scalability. Taken together, these are the critical factors that will ultimately determine whether MSRs can compete.
Proving durability where it matters In MSR designs pump reliability is a fundamental characteristic and presents particular challenges. Molten salt systems depend on continuous circulation of a liquid fuel and coolant material which is both corrosive and at a high temperature. While in contrast to many light water designs any failure in pumping systems may not affect safety, it does directly compromise reactor operation and therefore becomes a critical path system for plant economics. “Component reliability is not something you prove once,
it has to be proven repeatedly over long periods and under realistic conditions,” Copenhagen Atomics CEO and co- founder, Thomas Jam Pedersen, tells NEI, adding: “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.” Indeed, operating a molten salt pump continuously for two
years under conditions exceeding 600°C represents one of the longest continuous demonstrations of its kind globally. However, the import lies less in the face value operational duration than in what it represents for licensing and commercial deployment. Regulators do not approve reactors based on theoretical performance; they require extensive empirical data demonstrating that critical components can operate reliably over timescales comparable to operational lifetimes. Pedersen emphasises the significance of this point:
“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.”
Necessity as the mother of invention Copenhagen Atomics’ approach focuses on high-volume, low-cost experimentation. Rather than relying on a small number of expensive prototypes, the company has built a vertically integrated testing platform capable of running multiple molten salt loops in parallel. To date, the company reports more than 100,000 hours of combined pump runtime, with over 120 pumps tested and many exceeding one year of operation. This scale of testing is unusual in a field where individual test systems can cost millions of dollars. The rationale is both technical and economic, as Pedersen explains: “When you start combining temperature, flow rate and salt chemistry, you get a very large solution space that you need to explore and regulators don’t just want one result, they want to see variation across repeated tests.” Cost reduction is therefore critical. “If each test costs a million dollars, there’s a limit to how many you can run. But if you can get that down to maybe $10,000, then suddenly you can run many more tests and build statistically meaningful data.” This strategy has led to a level of experimental
throughput that Pedersen argues is unmatched: “We have more molten salt pumps here in Copenhagen than all the other teams testing molten salt reactors or equipment around the world combined.” The company’s decision to develop its own pump
Running an in-house designed molten salt pump continuously for two years is a major technical milestone for Copenhagen Atomics. Source: Copenhagen Atomics
90 | April 2026 |
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technology also illustrates how practical constraints have shaped its engineering approach. Early in its development, Copenhagen Atomics found that no existing supplier could provide a suitable high-temperature pump for molten salt applications. After contacting approximately 20 manufacturers, the only viable proposal involved a multi-year development effort costing around $1m and even then there were no guarantees of success. For Pedersen and the other co-founders this was untenable. The result was an in-house design based on a canned rotor configuration, in which the motor and impeller are integrated and enclosed, eliminating the need for long shafts and reducing leakage risks. This canned rotor pump model also contrasts with the cantilever designs more commonly proposed for molten salt systems. “It was really because we couldn’t find anything on the
market, but that forced us to develop something different and it turned out to work quite well,” Pedersen says. The design has since been patented and refined through
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