Next-gen nuclear reactors in US to get more efficient with Idaho’s new test bed

One of the key obstacles to bringing molten salt reactors to market has been the need for efficient and effective testing. To address this challenge, researchers at Idaho National Laboratory (INL) have developed a cutting-edge system that will accelerate the commercialization of molten salt reactors.

Revolutionizing testing with real-time monitoring

INL’s new Molten Salt Flow Loop Test Bed stands out from other testing systems due to its ability to perform continuous, real-time monitoring and analysis. Unlike other test loops, which often dismantle after only a few hours to study material degradation, INL’s system allows for ongoing testing of the materials while they remain in operation.

“Most test loops focus on testing the structural materials,” explained Ruchi Gakhar, the lead scientist at INL’s Advanced Technology of Molten Salts department. “After a few hours of operation, they dismantle the loop to study how the materials have degraded.”

“Our loop at INL is unique because it serves as a test bed for advanced electrochemical sensors and bubbler instruments,” Gakhar continued. “These instruments allow us to monitor and investigate material performance in real-time while the loop is still operational. This approach has not been implemented or explored in flow loops at other institutions.”

This new approach will allow researchers to assess how chloride salts—known for their ability to transfer heat efficiently and their affordability—behave in a flowing environment.

The use of these salts in molten salt reactors has been a point of interest, but researchers need to ensure that the salts flow smoothly and do not damage the reactors. INL’s test bed makes this possible by providing detailed insights into the behavior of the salts during operation.

Collaborating for a breakthrough reactor

INL is collaborating with Southern Company and TerraPower on a project called the Molten Chloride Reactor Experiment, which will demonstrate the world’s first operational fast-spectrum molten salt reactor. This experiment will help advance the understanding and development of molten salt reactors on a global scale.

In this collaboration, INL will play a major role by synthesizing and handling the fuel salt, operating the reactor, and performing post-operation deactivation and disassembly. The insights gained from the molten salt flow loop will be crucial to improving the longevity and reliability of these reactors, ultimately reducing costs and maintenance needs.

“This will be a big step toward building molten salt reactors that last longer and require less maintenance, reducing costs and improving reliability,” said John Carter, manager of the Advanced Technology of Molten Salts department at INL.

How the test bed works

The molten salt flow loop at INL operates similarly to a car radiator, which circulates coolant through the engine to maintain optimal temperature and prevent overheating. Just as the radiator is crucial for a car’s performance, the flow loop is essential for the molten salt reactor’s performance. It allows researchers to maintain precise temperature control and efficiently transfer heat, ensuring the system operates smoothly.

The loop is constructed from stainless steel, a highly durable material, and contains a special mixture of lithium chloride and potassium chloride salts. To keep the salts pure and free from contamination, an inert gas fills the space above the salts, much like how a car radiator cap prevents dirt from entering the coolant system.

The system also includes features that allow researchers to monitor material wear over time without interrupting the flow. Scientists can insert and remove samples while the system continues to operate, much like checking the oil in a running engine.

The test bed is equipped with five electrode ports for electrochemical experiments, enabling the real-time monitoring of the chemical state of the salt and any corrosion occurring in the system. Bubbler dip-tube ports measure fluid density, surface tension, and molten salt levels, while special devices monitor temperature changes throughout the system. This setup helps scientists better understand the heat transfer properties of molten salts.

“This work will accelerate us toward our advanced energy future,” said Carter. “It will enable development of advanced corrosion-resistant materials, sensors, and instrumentation for ultra-high-temperature applications.”