Most nuclear reactors in the U.S. today rely on solid pellets of uranium dioxide to operate. While these pellets get the job done, they aren’t very good at conducting heat. Because they hold onto that heat so stubbornly, the reactors need a constant, uninterrupted flow of water to stay cool. If that cooling stops, things quickly get complicated.

Researchers at Oak Ridge National Laboratory (ORNL) think they have found a way to fix this by changing the fuel’s physical state. Their new concept is called ULIMES, which stands for Uranium Dioxide Liquid Metal Suspension. Instead of hard pellets, they are using tiny uranium particles suspended in liquid metal.

A Liquid Upgrade for Reactor Safety

By shrinking the uranium down to small particles and mixing them into a liquid metal alloy, the fuel can flow through the reactor core. Metal is a much better heat conductor than solid ceramic pellets, so the fuel cools down more efficiently on its own.

This change means the reactor doesn’t need the same massive, complex cooling systems that current plants require. Because the fuel handles heat so much better, the whole design becomes simpler. It could lead to reactors that are cheaper to build and much easier to maintain, all while being safer because they don’t rely so heavily on a constant power source to keep pumps running.

Bridging the Gap

One of the best parts about this new fuel is that it doesn’t require engineers to reinvent the wheel. It works with the same types of materials already used in today’s light water reactors. This makes it a practical step forward rather than a sci-fi dream that’s decades away.

“ULIMES bridges today’s reactors with tomorrow’s technologies, using proven materials to provide next-generation performance without next-generation construction costs,” said ORNL’s Ian Greenquist.

To get this tech out of the lab and into the real world, ORNL has signed a research license agreement with an Australian investment firm, Out The Back Ventures. This funding will help push the research further, potentially changing how we think about everything from large-scale power grids to medical isotope production.