The crystallographic structure of the air-grown oxide on depleted uranium metal

Jones, Christopher P.; Petherbridge, James R.; Davis, Sean A.; Jones, Jonathan; Scott, Thomas Bligh

doi:10.1016/j.corsci.2016.05.036

Cited by 20 publications

(6 citation statements)

References 30 publications

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“…In most metallic nuclear materials, either only a very small dependence of the oxidation behaviour on different substrate orientations was found, e.g. in zirconium alloys [29], or in some cases, no variation at all was found, as is the case for uranium [30]. On the other hand, in non-metallic compounds such as uranium dioxide [31] a marked orientational dependence on aqueous dissolution was observed.…”

Section: Introductionmentioning

confidence: 99%

Probing the correlation between phase evolution and growth kinetics in the oxide layers of tungsten using Raman spectroscopy and EBSD

Fulton

Lunev

2020

Corrosion Science

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Tungsten, a plasma-facing material for future fusion reactors, may be exposed to air during abnormal operation or accidents. Only limited information is available on the evolution of related oxide phases. This work addresses the effect of substrate orientation on structural variations of tungsten oxides. Annealing experiments in an argon-oxygen atmosphere have been conducted at T = 400°C under varying oxygen partial pressure and oxidation time. A combination of EBSD, Raman spectroscopy and confocal microscopy shows preferential oxidation initially on {1 1 1} base material planes. The oxide scale changes its phase composition dynamically, influencing the kinetics of its growth.

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Section: Introductionmentioning

confidence: 99%

Probing the correlation between phase evolution and growth kinetics in the oxide layers of tungsten using Raman spectroscopy and EBSD

Fulton

Lunev

2020

Corrosion Science

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“…On the experimental U metal samples contacting humid atmospheres and water solutions, the hydration phenomenon ubiquitously takes place and considerably promotes the environmental degradation process of the native oxide films, especially at the reactive grainboundary sites. 3,5,8,10,11,14 Such a hydration process occurring at defect sites and its corrosion promoting effect can be understood more clearly by illustrating a similar example with the prototypical α-Al 2 O 3 . The compact corundum crystal structure of α-Al 2 O 3 films can provide superior protection to many metal and coating substrates in regular environments.…”

Section: = | |=mentioning

confidence: 98%

“…It is the spontaneously formed oxide films that serve as the native corrosion barriers for the metal substrates because of the reduced surface adsorption and blocked defect permeation. , Thus, in various chemical and mechanical treatment methods (e.g., alloying and ultrasonic surface rolling) that can obviously improve the corrosion resistance of actinide metals, , the key mechanisms are always associated with the optimized microscopic states of the native oxide films. The environmental water molecules may aggravate the breakdown of oxide films through accelerating the surface electrochemical reactions on these native outer-layer oxide films and then forming loose and pyrophoric hydrides at the oxide/metal interfaces. ,,− Apart from serving as the protective films on actinide metals, actinide oxides themselves are the major chemical forms for nuclear fission fuels. The traditional fuels mainly consist of UO 2 , plus some possible oxidization byproducts (e.g., U 4 O 9 , U 3 O 7 , U 3 O 8 , and UO 3 ). ,,,− Mixed-oxide fuels consisting of UO 2 and PuO 2 powders have also been developed for the new-generation fast breeder reactors, making it possible to dispose the industrial and military Pu in a more sustainable recycling approach. , The thermodynamic oxidations of UO 2 and PuO 2 under an environment, if not precisely predicted and appropriately controlled, will bring unexpected volume expansion and stress accumulation.…”

Section: Introductionmentioning

confidence: 99%

Environmental Stability of Actinide Oxides Mapped by Integrated and Accurate First-Principles Calculations

Sun,

Ye,

Zhang

et al. 2024

J. Phys. Chem. C

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The synthesis, storage, application, and disposal of various actinide materials in the fields of nuclear-fuel-based clean energy and actinide-metal-based metallurgy always closely correlate with the stabilities of U and Pu oxides in many atmospheric and aqueous environments. It is technologically important to jointly evaluate both the thermodynamic and electrochemical stabilities of actinide oxides there, for which free energy of formation (Δf G) is the key physical quantity. Due to various unavoidable technical and physical challenges in experiments, the Δf G data for these polyvalent oxides have long-standing inaccurate and incomplete problems. Here, we design an integrated first-principles approach to carry out efficient structural screenings, accurate energetic calculations by considering both the exact electronic potential and phononic contribution, and reliable mappings of the thermodynamic and electrochemical phase diagrams for anhydrous and hydrous actinide oxides in different environments (e.g., dry air, humid air, and aqueous solution). Based on the accurate and complete stability-composition-environment relationships constructed here, the established thermodynamic and electrochemical understandings can successfully explain versatile experimental observations on the hydration, oxidation, and corrosion behaviors of actinide oxides. Finally, the isotope effects on Δf G values are quantitatively predicted, revealing that any oxide will have nearly the same stability in environments with light and heavy waters. The systematically accurate electronic structure, thermodynamic stability, and electrochemical stability of actinide oxides as obtained in this work can provide many related theoretical and experimental studies in the future with reliable and desirable numerical references, as well as the comprehensively revealed physical and chemical mechanisms.

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“…In addition, UO 2 is the main product of the uranium oxidation reaction . Experimental findings reveal that the layer of uranium oxide formed in air consists of UO 2 nano-grains, averaging around 12 nm in grain size . The oxidation of uranium, being a diffusion-controlled process, is governed by the rate of oxygen diffusion through the defects, especially GBs, existing in the oxide layers. , Therefore, gaining a deep understanding of the characteristics of UO 2 GBs is vital for predicting fuel performance, safety, and longevity, as well as for elucidating and regulating uranium corrosion.…”

Section: Introductionmentioning

confidence: 99%

Quantifying Local Atomic Distortions in UO₂ Grain Boundaries: Correlation with Energetic and Electronic Properties

Zheng,

Wang,

Chen

et al. 2023

Inorg. Chem.

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UO 2 , as a key material in the nuclear industry, is composed of grains or crystallites in real applications. Their interfaces, known as grain boundaries (GBs), significantly impact thermal conductivity, corrosion resistance, and mechanical response. Here, utilizing Hubbard-corrected density functional theory, we systematically examine the local cluster structures, energetic stabilities, and electronic properties of five typical tilt UO 2 GBs ranging from Σ 3 to Σ 11. We categorize all possible distorted U-and O-centered clusters at these GBs and identify their cluster morphologies and radial and angular distortions. Our results highlight the abundance of new U−O bonds stretching to "medium-range", a feature often overlooked in conventional coordination analysis. To quantitatively describe these distorted clusters, we use smooth overlap of atomic positions (SOAP) to represent the structural and chemical local environments, which takes into account both radial (2-body) and angular (3-body) distortions. We define a dissimilarity index by computing the inner product of SOAP descriptors between the distorted and the perfect motif in ideal UO 2 . Our findings show that the medium-range SOAP dissimilarity correlates well with the GB excess energy, outperforming metrics such as dangling bonds or bonding strain. Furthermore, it is found that the band gaps in sufficiently high-energy GBs are shortened, with excess states primarily contributed by the distorted U clusters. Our results present a comprehensive gallery of the local distorted clusters introduced by typical UO 2 GBs and have implications on the structure−property relations of GBs and other interfaces.

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The crystallographic structure of the air-grown oxide on depleted uranium metal

Cited by 20 publications

References 30 publications

Probing the correlation between phase evolution and growth kinetics in the oxide layers of tungsten using Raman spectroscopy and EBSD

Probing the correlation between phase evolution and growth kinetics in the oxide layers of tungsten using Raman spectroscopy and EBSD

Environmental Stability of Actinide Oxides Mapped by Integrated and Accurate First-Principles Calculations

Quantifying Local Atomic Distortions in UO₂ Grain Boundaries: Correlation with Energetic and Electronic Properties

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The crystallographic structure of the air-grown oxide on depleted uranium metal

Cited by 20 publications

References 30 publications

Probing the correlation between phase evolution and growth kinetics in the oxide layers of tungsten using Raman spectroscopy and EBSD

Probing the correlation between phase evolution and growth kinetics in the oxide layers of tungsten using Raman spectroscopy and EBSD

Environmental Stability of Actinide Oxides Mapped by Integrated and Accurate First-Principles Calculations

Quantifying Local Atomic Distortions in UO2 Grain Boundaries: Correlation with Energetic and Electronic Properties

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Quantifying Local Atomic Distortions in UO₂ Grain Boundaries: Correlation with Energetic and Electronic Properties