Researchers at Lawrence Livermore National Laboratory (LLNL) have observed and characterized the initial stages of hydrogen-uranium corrosion for the first time.

“Critical advanced energy initiatives such as fusion energy, hydrogen storage, and nuclear fuels require an understanding of the metal-hydrogen degradation reaction,” said the researchers in a new study. 

“This knowledge enables characterizing tritium retention effects for improved plasma-facing component durability in fusion energy, material and containment reliability for hydrogen storage, and improved fuel cycle efficiency and lifespan for nuclear fuels.”

The team used a non-destructive imaging technique to record the start of the reaction.The findings will allow researchers to create more predictive models for how uranium components degrade over time.

“We achieved real-time tracking of the uranium surface in a hydrogen environment for an extended reaction time to collect the first-of-its-kind relevant degradation statistics that better define and aid modelling of uranium degradation,” added the study.

Akin to the “geyser” effect

When hydrogen gas interacts with uranium metal, the combination creates a reactive powder and a runaway reaction. 

LLNL scientist Jibril Shittu compared the interaction to a geyser. First, hydrogen dissolves and diffuses into the uranium metal. Once the uranium can no longer hold the gas, the two materials combine to form a new compound called uranium hydride.

Because uranium hydride takes up more volume than the original uranium metal, internal pressure increases. This pressure forces the material upward, creating a shallow blister on the surface. Eventually, the blister bursts, releasing uranium hydride powder and exposing fresh metal that accelerates the reaction.

“In short: adsorb, dissociate, diffuse, accumulate, blister, rupture, spall,” Shittu remarked. “That’s the cycle, and once it starts, it’s hard to stop.”

Tracking the start of the reaction

Historically, tracking the start of this reaction has been difficult. The two standard monitoring techniques in the field only function effectively after the reaction is well underway, leaving the initial events unrecorded.

To resolve this, the LLNL team used white-light interferometry. This method measures how light reflects off the uranium surface compared to a reference beam, creating a small topographic map. 

The technique does not touch or destroy the material. Therefore, the team repeatedly scanned the same surface throughout the entire reaction to build a frame-by-frame record.

The data revealed unexpected behaviors: the hydride blisters did not appear where models predicted, and the corrosion spread horizontally across the surface rather than deep into the metal.

Could transfer to other fields

“This work was done at a narrow temperature range and a single hydrogen pressure and material state,” noted the team in a press release. “The next step is to extend it across a wider range of conditions.”

The non-contact imaging method could also transfer to other fields, such as investigating degradation in hydride superconductors or general industrial metal corrosion.

“The result will lead to more predictive and physically grounded models for how uranium components degrade,” concluded the researchers.

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