Lawrence Livermore researchers film hydrogen corrosion of uranium

Lawrence Livermore Researchers Film Uranium Destruction

A continuous topographical movie recorded at Lawrence Livermore National Laboratory captured the exact moment hydrogen gas initiates a severe corrosion cycle on solid uranium, turning the dense metal into a highly reactive powder. For more than 75 years, researchers struggled to observe the start of this degradation reaction because traditional testing methods relied entirely on measuring changes in overall gas pressure or total weight. Those legacy techniques lacked microscale sensitivity, leaving laboratories blind to the initial moments of surface failure. Engineers working on nuclear energy and fusion systems confront this vulnerability constantly, as hydrogen degrades internal metals and threatens depleted uranium used as radiation shielding for spent fuel.

The Tech TL;DR:

• Researchers used white-light interferometry (WLI)—acting as an ultra-precise 3D camera—to bounce light waves off solid uranium without touching the delicate sample.
• When exposed to hydrogen at 122 degrees Fahrenheit and 2 psi, the metal surface remained unchanged for 62 minutes before the first hydride blister appeared.
• Once the protective surface ruptured at 78 minutes, fresh metallic uranium was exposed, causing 42.7% of the surface area to degrade within four hours.

High-Resolution Optical Profiling Exposes the Geyser Cycle

To overcome the limitations of weighing entire samples to find microscopic cracks, the Lawrence Livermore team adapted high-resolution optical profiling. White-light interferometry mapped the metal at a sub-microscopic level, revealing a physical degradation cycle resembling a geyser. Hydrogen gas dissolves and diffuses into uranium until it exceeds solubility limits, forming uranium hydride that expands significantly and builds intense subsurface pressure. Real-time WLI tracking recorded the precise timeline of this destruction. At 122 degrees Fahrenheit and 2 psi, the first hydride blister emerged after 62 minutes. At 78 minutes, that blister reached a critical spallation threshold—measuring 1.79 micrometers in height and 17.58 micrometers in diameter—cracking the outer metal and releasing fine uranium hydride powder.

Hydride Blisters Grow Horizontally from Uranium Carbide Impurities

Continuous imaging disproved long-term assumptions regarding where hydride blisters originate on a polished metal surface. Focused ion beam sectioning revealed that growth centers did not form preferentially at casting pores, but instead aligned with uranium carbide impurities and microscopic structural cracks. Cross-sectional tomography showed that subsurface hydrides do not drill deep into the core; rather, the hydride expands horizontally in an oblate shape along the surface boundary. Quantifying this behavior allowed scientists to measure a stable spall-front velocity of 0.91 micrometers per minute as the metal cracks and flakes off.

Implications for Spent Fuel Shielding and Fusion Reactors

Establishing precise degradation models helps engineers design safer long-term storage solutions for depleted uranium used to shield spent nuclear fuel. Understanding the mechanics behind this metal–hydrogen reaction provides critical knowledge for engineering durable, plasma-facing components for future fusion systems.