Recognition of uranium oxides in soil particulate matter by means of μ-Raman spectrometry

Stefaniak, E.; Alsecz, Anita; Sajó, István E.; Worobiec, Anna; Máthé, Z.; Török, Szabina; Grieken, R. Van

doi:10.1016/j.jnucmat.2008.08.036

Cited by 61 publications

(48 citation statements)

References 15 publications

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“…Two sets of FLiNaK melts were prepared by adding Li 2 O. The Raman spectrum of this precipitates is consistent with that of UO 2 reported by Stefaniak et al, 38 as shown in Fig. One set was added with ZrF 4 to achieve n Zr /n O ¼ 7.0, while the other set was not (n Zr /n O ¼ 0).…”

Section: The Mechanism Of Zrf 4 Protection Against the Uo 2 Precipitasupporting

confidence: 82%

Chemical interactions between zirconium and free oxide in molten fluorides

et al. 2015

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The chemical interactions between zirconium and free oxide in FLiNaK melts at different zirconium to oxide (n Zr /n O ) molar ratios were studied by means of a carbothermal-reduction technique (LECO oxide analyzer) and Raman spectroscopy. ZrO 2 precipitates were formed with n Zr /n O # 0.5, while ZrO 2 was converted to Zr 2 OF x 6Àx complexes with n Zr /n O > 0.5. The maximum amount of Zr 2 OF x 6Àx complexes in FLiNaK melts was found to be 0.020 mol kg À1 . With an initial oxide concentration lower than 0.020 mol kg À1 and the required amount of ZrF 4 , the free oxide in FLiNaK melts could be completely converted to Zr 2 OF x 6Àx complexes, which would further prevent the formation of UO 2 precipitates. Fig. 9 The Raman spectra of UO 2 (ref. 38) ore and the bottom precipitates taken from the solidified FLiNaK-UF 4 (0.007 mol kg À1 ) melts at initial oxide ¼ 0.020 mol kg À1 and n Zr /n O ¼ 0. Fig. 8 The solidified FLiNaK melts with initial oxide at 0.020 mol kg À1 and different n Zr /n O ; (a) n Zr /n O ¼ 0; (b) n Zr /n O ¼ 7.0. 40712 | RSC Adv., 2015, 5, 40708-40713This journal is

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Section: The Mechanism Of Zrf 4 Protection Against the Uo 2 Precipitasupporting

confidence: 82%

Chemical interactions between zirconium and free oxide in molten fluorides

et al. 2015

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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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“…Representative spectra are shown in Figure 3. The U-doped samples also show the presence of two broad peaks centered at ~740 and ~700 cm -1 , which are typical for a U 6+ structure (γ-UO 3 ) and have been assigned to the O-U-O-U (700 cm -1 ) and U-O (740 cm -1 ) stretching vibrations [18,19]. The U-doped samples also show the presence of two broad peaks centered at ~740 and ~700 cm -1 , which are typical for a U 6+ structure (γ-UO 3 ) and have been assigned to the O-U-O-U (700 cm -1 ) and U-O (740 cm -1 ) stretching vibrations [18,19].…”

Section: Discussionmentioning

confidence: 97%

The Structural Characterization of a Series of Uranium-containing Gadolinium Zirconates

Gregg

Zhang

et al. 2012

MRS Proc.

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A series of uranium-containing gadolinium zirconate samples have been fabricated at 1723 K in air. X-ray diffraction and Raman spectroscopy have confirmed pyrochlore or defect fluorite structures, while diffuse reflectance, X-ray absorption near edge structure and X-ray photoelectron spectroscopies indicate a predominantly U 6+ oxidation state, even when Ca 2+ was added to charge balance for U 4+ . The results demonstrate the potential of gadolinium zirconates as host materials for actinides.

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Recognition of uranium oxides in soil particulate matter by means of μ-Raman spectrometry

Cited by 61 publications

References 15 publications

Chemical interactions between zirconium and free oxide in molten fluorides

Chemical interactions between zirconium and free oxide in molten fluorides

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

The Structural Characterization of a Series of Uranium-containing Gadolinium Zirconates

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