UH3 produced at the initial stage of U-H2O corrosion

Li, Haibo; Wang, Shuaipeng; Gan, Li; Wu, Haoxi; Pu, Zhen; Ren, Bin; Luo, Wenhua

doi:10.1016/j.corsci.2023.111143

Cited by 2 publications

(3 citation statements)

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“…The electrochemical hydration tendency of actinide oxides deserves special discussion because the resultant loose atomic structures (see Figure S5) will be adverse to the corrosion resistance of native oxide films. 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 grain-boundary sites. ,,,,, 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. , However, as revealed by the Al Pourbaix diagram (see Figure S12), the hydration process of Al 2 O 3 is exothermic and will be stimulated by hot water vapors.…”

Section: Resultsmentioning

confidence: 99%

“…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: 99%

“…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%

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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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