New insight into δ-Pu alloy oxidation kinetics highlighted by using in-situ X-ray diffraction coupled with an original Rietveld refinement method

Ravat, B.; Jolly, L.; Oudot, B.; Fabas, Aurélien; Guérault, Hugues; Popa, Iolanda Valentina; Delaunay, F.

doi:10.1016/j.corsci.2018.03.046

Cited by 25 publications

(8 citation statements)

References 42 publications

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“…The P–T diagram for Pu oxides in dry air also exhibit the prevailing appearance of PuO 2 as the most-stable oxide in all the considered phase space (Figure e). This is fully consistent with the experimental observations on the oxidation behaviors of Pu metal at temperatures of 300–1000 K and pressures of 10 –9 ∼ 0.1 bar, ,− where it is PuO 2 on the top layer to contact with the environmental atmosphere. Another oxide Pu 2 O 3 only forms between the PuO 2 layer and metal substrate due to the insufficient O atoms there, and Pu 2 O 3 is also a favored composition that resides on the convex-hull line (i.e., free from spontaneous decomposition, see Figure c).…”

Section: Resultssupporting

confidence: 90%

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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Section: Resultssupporting

confidence: 90%

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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“…Exposures were carried out in a reaction chamber (TTK 450 Anton Paar) directly mounted on a θ/θ diffractometer (BRUKER AXS D8 Advance) located inside a glovebox. Diffraction patterns were recorded in situ during the exposure, and have been analyzed using a modified Rietveld refinement method described in [11]. In addition, grazing incidence XRD analysis (E=10 keV) was performed on oxidized samples, using a 2D Pilatus detector on the MARS beamline at the SOLEIL synchrotron facility.…”

Section: Experimental Details and Methodsmentioning

confidence: 99%

“…It consists of a parabolic step with the formation of a compact oxide layer, followed by a linear step with the occurrence of cracks in the oxide scale. Ravat et al [11] have shown, by using in situ XRD analyses, that the parabolic growth results from the formation of Pu2O3, while the linear growth is exclusively induced by the growth of PuO2. The influence of Ga, used as a −phase stabilizer element, on oxidation has also been investigated.…”

Section: Introductionmentioning

confidence: 99%

Characterization of PuGa (1at%. Ga) Oxidation under Dry Oxygen Atmosphere Exposure

Favart,

Ravat,

Jolly

et al. 2024

Preprint

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The oxidation of δ−stabilized plutonium alloy has been studied under dry oxygen exposures for temperatures varying from 100°C up to 300°C and oxygen partial pressures varying from 10− 4 up to 500 mbar. The coupling of X-ray diffraction, Raman spectroscopy and FIB-SEM has allowed to show that the oxide scale is composed of an outer layer of PuO2 and an inner mixed layer of α+β−Pu2O3 platelets propagating into a metallic zone corresponding to the stable phase of unalloyed Pu. Furthermore, the analysis of Pu oxidation kinetics has displayed first a parabolic growth governed by the diffusion of interstitial oxygen. This step consists in the thickening of the Pu2O3 layer with a decrease in α−Pu2O3 ratio in favour of β−Pu2O3. Then, a second step occurs consisting in a linear growth of the PuO2−layer with the formation of thick nodules which tend to cover the whole oxide surface. Based on the results of this work, a general oxidation mechanism for δ−Pu alloy is provided.

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“…Plutonium is also extremely reactive forming compounds or alloys with the majority of the elements in the periodic table 2 . The oxophillic nature of plutonium means the metal is typically covered with an oxide film where the rate of reaction is significantly enhanced by the presence of moisture at room temperature 3,4 . In addition to the physical properties described above, plutonium is radioactive and toxic which requires special handling facilities and scientific equipment modified or designed to contain possible contamination.…”

Section: Introductionmentioning

confidence: 99%

Quantitative XPS of plutonium: Evaluation of the Pu4f peak shape, relative sensitivity factors and estimated detection limits

Roussel

Nelson

2022

Surface & Interface Analysis

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High-resolution X-ray photoelectron spectra have been acquired from sputter cleaned and in situ oxidized samples of α-plutonium and a face-centred cubic δ-plutonium-gallium alloy. The differences in the Pu4f peak shape in these two materials have been investigated, and the poorly screened satellite peaks have been quantified.Curve fitting parameters for the Pu4p 3/2 , Pu4d 5/2 , Pu4f and Pu6p 3/2 photoelectron peaks are reported, and relative sensitivity factors have been determined. The Pu4f curve fit model has been applied to data acquired using different spectrometers and alloys. Examples of quantification of the plutonium spectra are provided and minimum detection limits are calculated for common impurities in plutonium metal.

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New insight into δ-Pu alloy oxidation kinetics highlighted by using in-situ X-ray diffraction coupled with an original Rietveld refinement method

Cited by 25 publications

References 42 publications

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

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

Characterization of PuGa (1at%. Ga) Oxidation under Dry Oxygen Atmosphere Exposure

Quantitative XPS of plutonium: Evaluation of the Pu4f peak shape, relative sensitivity factors and estimated detection limits

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