Molten salt could reshape the future of nuclear energy

The intricate dance of uranium trichloride (UCl3), a molten salt under extremely high temperatures, holds the key to unlocking the full potential of next-generation nuclear reactors.

Its unique properties, when transformed into a liquid state, offer unparalleled opportunities to rethink nuclear fuel technology and improve reactor safety and efficiency.

Researchers from the Oak Ridge National Laboratory (ORNL) and their collaborators have meticulously documented, for the first time, the elusive structure and complex chemistry dynamics of high-temperature liquid UCl3 salt.

Promising source of nuclear energy

The research positions this substance as a promising source of nuclear fuel. The critical insights pave the way for designing safer, more efficient, and innovative reactors that could reshape the future of nuclear energy.

In a paper published in the Journal of the American Chemical Society, ORNL researcher Santanu Roy noted that this is a first critical step in enabling good predictive models for the design of future reactors.

“A better ability to predict and calculate the microscopic behaviors is critical to design, and reliable data helps develop better models,” said Roy.

The study highlights the significant leap toward understanding the behavior of molten uranium salts.

Nuclear energy and molten salt reactors

For decades, molten salt reactors have been seen as a promising solution for producing safe and affordable nuclear energy.

ORNL’s prototyping experiments in the 1960s demonstrated the potential of this technology. With the global push for decarbonization, there has been renewed interest in making these reactors widely available.

However, designing the ideal system requires a deep understanding of how liquid fuel salts behave, particularly those involving actinide elements such as uranium.

Molten salts, which melt at extremely high temperatures, exhibit complex ion-ion coordination, making them challenging to study.

State-of-the-art neutron scattering studies

The research was a collaboration between ORNL, Argonne National Laboratory, and the University of South Carolina. The team utilized a combination of computational approaches and advanced facilities like the Spallation Neutron Source (SNS).

As one of the brightest neutron sources in the world, SNS allowed the team to perform state-of-the-art neutron scattering studies, enabling them to measure the chemical bond lengths of molten UCl3 for the first time.

“I’ve been studying actinides and uranium since I joined ORNL as a postdoc,” said Alex Ivanov, who co-led the study. “But I never expected that we could go to the molten state and find fascinating chemistry.”

The findings revealed that, unlike most substances, the bonds between uranium and chlorine contracted rather than expanded as the substance became liquid.

Breaking stereotypes in chemistry

One of the most surprising discoveries was the inconsistent behavior of the bonds, which oscillated between expanded and contracted states at ultra-fast speeds.

“This is an uncharted part of chemistry and reveals the fundamental atomic structure of actinides under extreme conditions,” noted Ivanov.

The bond lengths exhibited varying patterns, occasionally becoming shorter and temporarily transforming from an ionic to a more covalent nature. This fleeting change helped explain inconsistencies in previous studies.

These findings, along with the broader results of the study, will improve both experimental and computational approaches to reactor design, while also shedding light on challenges such as nuclear waste management and pyroprocessing.

Unlocking the future of nuclear energy

The insights gained from this study not only deepen our understanding of molten uranium salts but also highlight their potential in revolutionizing nuclear energy production.

With the unpredictable behavior of UCl3 now more clearly defined, the path to developing more efficient and safer nuclear reactors becomes clearer.

These breakthroughs could play a crucial role in addressing challenges related to nuclear waste, pyroprocessing, and the advancement of sustainable nuclear technologies.

By improving predictive models and expanding the knowledge of molten salt behavior, scientists are one step closer to creating reactors that can help meet global energy demands while minimizing environmental impact.

As nuclear energy remains a key player in the race toward decarbonization, the discoveries in this study offer hope for more reliable, scalable, and eco-friendly energy solutions in the near future.

The study is published in the Journal of the American Chemical Society.

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