Hydrogen Interactions with Uranium Materials

Hydrogen exhibits multifaceted interactions with uranium and its alloys, profoundly influencing corrosion, phase stability and long-term storage safety. When hydrogen contacts uranium metal, it can adsorb onto the surface, dissociate and diffuse into the bulk, leading to the nucleation and growth of uranium hydride (UH3). This reaction is accompanied by a significant volume expansion and the emergence of brittle hydride layers, which compromise structural integrity and generate pyrophoric risk in air. Environmental factors such as temperature, pressure, microstructure and surface condition govern the kinetics of adsorption, diffusion and hydride formation. In storage and legacy waste contexts, incomplete oxidation of UH3 layers under water vapour or aqueous conditions contributes to prolonged hydride persistence, with implications for burn-up and oxidation models. Computational studies at the atomic scale have elucidated site-specific adsorption energies and diffusion pathways, linking orbital hybridisation between hydrogen 1s and uranium 5f/6d states to stability trends. Collectively, these insights underpin improved design of corrosion mitigation strategies, inform safety assessments for uranium handling and guide alloy development for hydrogen tolerance.

Research from Nature Portfolio

Recent studies have probed the reaction of uranium hydride powder with saturated water vapour under ambient conditions. Kinetic measurements reveal a rapid initial oxidation stage followed by a decelerating, quasi-linear regime characteristic of a shrinking-core mechanism. Analysis of evolved gases indicates that the hydride-to-oxide conversion remains incomplete, reinforcing evidence for UH3 persistence in storage environments. From gas-phase composition and residual gas analysis, a mechanistic scheme has been proposed in which hydrogen evolution and surface diffusion control the progression of UO2 formation. These findings refine models of hydride stability in legacy waste and illuminate pathways for controlled oxidation under moisture exposure.

Research from all publishers

A comprehensive review of uranium-hydrogen corrosion over seven decades has mapped the thermodynamics and kinetics of UH3 formation, decomposition and oxidation. The survey highlights the critical roles of grain boundaries, surface strain and environmental humidity in dictating hydride nucleation rates, and analyses pyrophoric hazard in storage scenarios. First-principles calculations on α-uranium surfaces have identified two stable adsorption sites for hydrogen atoms and detailed energy barriers for atomic diffusion between surface and subsurface sites. Electronic structure analysis demonstrates hybridisation between hydrogen 1s orbitals and uranium 5f/6d states, correlating with increases in work function and enhanced surface stability. Spectroscopic examinations of corroded uranium have uncovered subsurface strain transition regions beneath hydride craters. Secondary ion mass spectrometry and X-ray photoelectron spectroscopy confirm covalent U–H bonding in these zones, leading to a micro-scale induction period before stoichiometric UH3 forms. Together, these experimental and computational approaches converge to clarify atomic-scale interactions and inform macroscopic corrosion models.

Hydrogen Interactions with Uranium Materials publication trend

The graph below shows the total number of articles in hydrogen interactions with uranium materials across all publications each year (not limited to Nature Index journals).

Technical terms

Uranium hydride (UH3): Intermetallic compound formed when hydrogen reacts with uranium metal, often pyrophoric and volumetrically expansive.

Shrinking-core mechanism: Oxidation model in which the reactive front moves inward from the particle surface, leaving an unreacted core.

First-principles calculations: Quantum mechanical simulations, typically based on density functional theory, predicting material properties without empirical parameters.

Work function: Minimum energy required to remove an electron from a solid to a point immediately outside its surface.

Hydride nucleation: Initial formation of discrete UH3 phases on or within a uranium substrate, often influenced by defects and surface strain.

References

1. A review of uranium corrosion by hydrogen and the formation of uranium hydride. Corrosion Science (2018).
2. An Investigation on the Persistence of Uranium Hydride during Storage of Simulant Nuclear Waste Packages. PLOS ONE (2015).
3. The kinetics and mechanism of the uranium hydride - water vapour system under ambient conditions. Scientific Reports (2020).
4. First-principles study of adsorption, dissociation, and diffusion of hydrogen on α-U (110) surface. AIP Advances (2024).
5. Mechanism of surface uranium hydride formation during corrosion of uranium. npj Materials Degradation (2019).