Layered uranium(<scp>vi</scp>) hydroxides: structural and thermodynamic properties of dehydrated schoepite α-UO<sub>2</sub>(OH)<sub>2</sub>

Weck, Philippe F.; Kim, Eunja

doi:10.1039/c4dt02455a

Cited by 37 publications

(47 citation statements)

References 45 publications

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“…The UO 2 sample, OU1, has an empirical oxygen yield of 3.6 μmol mg −1 , which matches the theoretical yield of 3.7 μmol mg −1 , and has also a highly reproducible δ 18 O conventional value (1 s < 0.2‰, n = 4). The UO 3 samples, LAR and JU‐21, have empirical oxygen yields of 21% (6.3 μmol mg −1 ) and 25% (6.5 μmol mg −1 ) greater than that expected from the chemical formula taken without any water molecule (5.2 μmol mg −1 ), meaning their theoretical formula can be a mix between different hydration states of schoepite (Finch and Ewing , Weck and Kim ). Indeed, in the structural formula UO 3 .…”

Section: Resultsmentioning

confidence: 99%

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF₅ Fluorination

Dierick

Pili

Assayag

et al. 2017

Geostandard Geoanalytic Res

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A new method for accurate determination of oxygen isotopes in uranium oxides encountered in the nuclear fuel cycle was developed using the conventional BrF5 fluorination technique. Laser‐assisted fluorination was tested for comparison. We focused on fine powders of triuranium octoxide (U3O8), uranium dioxide (UO2±x with 0 ≤ x ≤ 0.25), uranium trioxide (UO3.nH2O, with 0.8 ≤ n ≤ 2) and diuranates (M2U2O7.nH2O, with M = NH4, Na or Mg0.5 and 0 ≤ n ≤ 6). Fluorination at room temperature and heating under vacuum at 150 °C are shown to eliminate both adsorbed and structural water from the powder samples. Precision fit for purpose of δ18O values (± 0.3‰, 1s) and oxygen yields (close to 100%) were obtained for U3O8 and UO2 where oxygen is only bound to uranium. A lower precision was observed for UO3.nH2O and M2U2O7.nH2O where oxygen is both present in the structural H2O and bonded to uranium and where the extracted O2(g) can be contaminated by NF3 and NOx compounds. Laser‐assisted fluorination gave shifted δ18O values between +0.8 and +1.4‰ for U3O8, around −0.8‰ for UO3.nH2O and between −3.9 and −4.5‰ for M2U2O7.nH2O (± 0.3‰, 1s) compared with the conventional method.

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Section: Resultsmentioning

confidence: 99%

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF₅ Fluorination

Dierick

Pili

Assayag

et al. 2017

Geostandard Geoanalytic Res

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“…Because the corresponding information is available for anhydrous species, thermodynamic computations have been performed for the uraniumoxygen and sodium-uranium-oxygen system [85][86][87][88][89][90][91][92][93][94][95]. A detailed analysis of previous studies [41,[96][97][98][99][100][101][102][103][104][105] suggests that first principles methodology is an excellent complement to experimental methodology for determining the thermodynamic functions of these materials.…”

Section: Introductionmentioning

confidence: 99%

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Ruiz¹

2019

Density Functional Theory

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With the advent of increased computer capacities, improved computational resources, and easier access to large-scale computer facilities, the use of density functional theory methods has become nowadays a frequently used and highly successful approach for the research of solid-state materials. However, the study of solid materials containing heavy elements as lanthanide and actinide elements is very complex due to the large size of these atoms and the requirement of including relativistic effects. These features impose the availability of large computational resources and the use of high quality relativistic pseudopotentials for the description of the electrons localized in the inner shells of these atoms. The important case of the description of uranyl-containing materials and their properties has been faced recently. The study of these materials is very important in the energetic and environmental disciplines. Uranyl-containing materials are fundamental components of the paragenetic sequence of secondary phases that results from the weathering of uraninite ore deposits and are also prominent phases appearing from the alteration of the spent nuclear fuel. The development of a new norm-conserving relativistic pseudopotential for uranium, the use of energy density functionals specific for solids, and the inclusion of empirical dispersion corrections for describing the long-range interactions present in the structures of these materials have allowed the study of the properties of these materials with an unprecedented accuracy level. This feature is very relevant because these methods provide a safe, accurate, and cheap manner of obtaining these properties for uranium-containing materials which are highly radiotoxic, and their experimental studies demand a careful handling of the samples used. In this work, the results of recent applications of theoretical solid state methods based on density functional theory using plane waves and pseudopotentials to the determination of the thermodynamic properties and stability of uranyl-containing materials are reviewed. The knowledge of these thermodynamic properties is indispensable to model the dynamical behavior of nuclear materials under diverse geochemical conditions. The theoretical methods provide

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“…In fact, for a numerous set of materials in which uranium exists with VI oxidation state, the standard DFT description provides a reliable description of their structures and properties. [113][114][115][116][117][118][119][120][121][122][123][124][125][139][140][141][142][143][144][155][156][157][158][159][160][161][162] 2.2.2. Elastic tensor and equation of state.…”

Section: Introductionmentioning

confidence: 99%

Structural, mechanical, spectroscopic and thermodynamic characterization of the copper-uranyl tetrahydroxide mineral vandenbrandeite

et al. 2019

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Layered uranium(vi) hydroxides: structural and thermodynamic properties of dehydrated schoepite α-UO₂(OH)₂

Cited by 37 publications

References 45 publications

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF₅ Fluorination

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF₅ Fluorination

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Structural, mechanical, spectroscopic and thermodynamic characterization of the copper-uranyl tetrahydroxide mineral vandenbrandeite

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Layered uranium(vi) hydroxides: structural and thermodynamic properties of dehydrated schoepite α-UO2(OH)2

Cited by 37 publications

References 45 publications

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF5 Fluorination

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF5 Fluorination

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Structural, mechanical, spectroscopic and thermodynamic characterization of the copper-uranyl tetrahydroxide mineral vandenbrandeite

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Layered uranium(vi) hydroxides: structural and thermodynamic properties of dehydrated schoepite α-UO₂(OH)₂

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF₅ Fluorination

Enhanced Oxygen Isotope Determination in Uranium Oxides Using BrF₅ Fluorination