Raman spectroscopy characterization of actinide oxides (U1−yPuy)O2: Resistance to oxidation by the laser beam and examination of defects

Jégou, Christophe; Caraballo, R.; Peuget, S.; Roudil, D.; Desgranges, Lionel; Magnin, Magali

doi:10.1016/j.jnucmat.2010.08.005

Cited by 77 publications

(63 citation statements)

References 37 publications

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“…Absorbance bands are observed at $764 cm À1 and $838 cm À1 . Comparison of these bands with Raman bands of common uranium oxide/hydroxide/nitrate compounds reported in the literature [31,36,38,[44][45][46][47][48], reveals that the Raman spectrum of the cracked base layer is consistent with it being at least in part comprised of polymeric hydrated UO 2 2+ , as suggested by dos Santos et al [36], main bands at $740 and $822 cm À1 . In their analysis dos Santos et al also indicate that this polymeric hydrated UO 2 2+ is structurally akin to UO 3 (vide supra), a conclusion that is supported by the main bands of orthorhombic c-UO 3 being observed at 768 and 845 cm À1 .…”

Section: Characterisation Of Electroplated Uranium Oxide Filmssupporting

confidence: 62%

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

Wilbraham

Boxall

Goddard

et al. 2015

Journal of Nuclear Materials

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h i g h l i g h t sThe first report of the presence of both UO 2 and polymeric UO 2 2+ in the same electrodeposited U oxide sample.The action of H 2 O 2 on electrodeposited U oxides is described using corrosion based concepts.Electrodeposited U oxide freely dissolves at hydrogen peroxide concentrations <100 lmol dm À3 .At [H 2 O 2 ] > 0.1 mmol dm À3 dissolution is inhibited by formation of a studtite passivation layer. At [H 2 O 2 ] P 1 mol dm À3 studtite formation competes with uranyl-peroxide complex formation. a b s t r a c tFor the first time the effect of hydrogen peroxide on the dissolution of electrodeposited uranium oxide films on 316L stainless steel planchets (acting as simulant uranium-contaminated metal surfaces) has been studied. Analysis of the H 2 O 2 -mediated film dissolution processes via open circuit potentiometry, alpha counting and SEM/EDX imaging has shown that in near-neutral solutions of pH 6.1 and at [H 2 O 2 ] 6 100 lmol dm À3 the electrodeposited uranium oxide layer is freely dissolving, the associated rate of film dissolution being significantly increased over leaching of similar films in pH 6.1 peroxide-free water. At H 2 O 2 concentrations between 1 mmol dm À3 and 0.1 mol dm À3 , formation of an insoluble studtite product layer occurs at the surface of the uranium oxide film. In analogy to corrosion processes on common metal substrates such as steel, the studtite layer effectively passivates the underlying uranium oxide layer against subsequent dissolution. Finally, at [H 2 O 2 ] > 0.1 mol dm À3 the uranium oxide film, again in analogy to common corrosion processes, behaves as if in a transpassive state and begins to dissolve. This transition from passive to transpassive behaviour in the effect of peroxide concentration on UO 2 films has not hitherto been observed or explored, either in terms of corrosion processes or otherwise. Through consideration of thermodynamic solubility product and complex formation constant data, we attribute the transition to the formation of soluble uranyl-peroxide complexes under mildly alkaline, high [H 2 O 2 ] conditions -a conclusion that has implications for the design of both acid minimal, metal ion oxidant-free decontamination strategies with low secondary waste arisings, and single step processes for spent nuclear fuel dissolution such as the Carbonate-based Oxidative Leaching (COL) process.

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Section: Characterisation Of Electroplated Uranium Oxide Filmssupporting

confidence: 62%

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

Wilbraham

Boxall

Goddard

et al. 2015

Journal of Nuclear Materials

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“…However, more bands were experimentally observed in Raman spectrum of UO 2 . Graves first observed a broad band around 576 cm −1 for Kr + implanted UO 2 samples, which was confirmed by other groups . It is a disorder/defect induced band and generally assigned to the normally forbidden first‐order longitudinal optical phonon (1LO), which can become Raman active through a loss of symmetry because of a breakdown in the selection rules.…”

Section: Introductionmentioning

confidence: 58%

Raman scattering from phonons and electronic excitations in UO₂with different oxygen isotopes

Gan

Guo

et al. 2015

J. Raman Spectrosc.

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Comparison of the phonons and electronic excitations of UO2 with different oxygen isotopes (16O, 18O), two purely electronic excitations at 4162 and 5778 cm−1 have been evidenced by their limited shift, when 16O is replaced by 18O. The bands observed at 570, 1144 and 2300 cm−1 in U16O2 shift to 545, 1091 and 2190 cm−1 for U18O2. The wavenumbers and the isotope shifts of these bands exhibit multiple relationships. It supports the assignments of the 1LO (~570 cm−1) and 2LO (~1144 cm−1) phonons for U16O2. Both bands exhibit marked decrease for increasing O/U ratio. The observed phenomenon is regarded as a good estimation of the stoichiometry of a uranium oxide. In addition, by analyzing the intensity ratios of the 2LO to 1LO phonons for various UO2 samples, the 2LO band is assigned to the Fröhlich interaction. Defect‐induced and/or deformation potential mechanisms play a dominant role for the 1LO band. Copyright © 2015 John Wiley & Sons, Ltd.

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“…It is known that solid solutions containing oxygen vacancies are sensitive to oxidation . Oxidation of the sample by increasing laser power as a heat source was reported by Palacious on UO 2 and Jégou on UO 2 and (U 1− y Pu y )O 2 samples. Oxidation of the samples under Kr + laser beam was shown by recording the spectra sequentially on the same point of the sample at the consecutive laser powers (I) 2, (II) 6, and (III) 13 mW (at the exit of the laser cavity).…”

Section: Resultsmentioning

confidence: 92%

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

et al. 2015

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UO 2 samples doped with 6, 11, 22 mol% lanthanum were examined before and after air oxidation. To verify the formation of uranium-lanthanum-mixed oxide solid solutions, powder X-ray diffraction (XRD) analyses of the crystalline phases in the materials were carried out. The presence of oxygen vacancies in the La-doped UO 2 samples was identified by Raman spectrometry. It was evidenced by changes induced in the Raman spectra by air oxidation. This latter was carried out either by increasing the Raman laser power or by thermally treating the samples at 500 K for 370 h. In addition, oxidation behavior differences of pure and La-doped UO 2 samples were reported by comparing XRD and Raman results of the samples before and after air oxidation. It was shown that the concentration of the M 4 O 9 (M: U, La) phase increased with increasing content of La, whereas inhibition for the formation of M 3 O 8 phase was observed.

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Raman spectroscopy characterization of actinide oxides (U1−yPuy)O2: Resistance to oxidation by the laser beam and examination of defects

Cited by 77 publications

References 37 publications

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

Raman scattering from phonons and electronic excitations in UO₂with different oxygen isotopes

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

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Raman spectroscopy characterization of actinide oxides (U1−yPuy)O2: Resistance to oxidation by the laser beam and examination of defects

Cited by 77 publications

References 37 publications

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

Raman scattering from phonons and electronic excitations in UO2with different oxygen isotopes

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

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Raman scattering from phonons and electronic excitations in UO₂with different oxygen isotopes