From uranium(IV) oxalate to sintered UO 2 : Consequences of the powders' thermal history on the microstructure

Martinez, Julien; Clavier, Nicolas; Ducasse, Thomas; Mesbah, Adel; Audubert, Fabienne; Corso, Bruno; Vigier, Nicolas; Dacheux, Nicolas

doi:10.1016/j.jeurceramsoc.2015.07.010

Cited by 28 publications

(35 citation statements)

References 56 publications

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“…Finally, it is worth noting that a slight weight loss signal was recorded between 500 and 1000°C, and associated with the detection of small amounts of CO and CO 2 , which could be assigned to the elimination of residual carbon in the sample. Indeed, the thermal decomposition of MO 2 precursors, including carboxylates such as oxalates, was systematically associated with the presence of amorphous carbon within the final oxides 39,40 .…”

Section: Thermal Behaviour Of Uo 2 Particlesmentioning

confidence: 99%

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate

et al. 2018

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Section: Thermal Behaviour Of Uo 2 Particlesmentioning

confidence: 99%

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate

et al. 2018

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“…The initial yellow pellet became a black powder -likely losing oxalate ligands and reducing to UO2 within the environment of Flattop. Typically the decomposition of the oxalate species occurs between 300 and 400 °C in vacuum, 100 (Figure 70) shows that fission products can be extracted from the target diameter UO2 particles, although the yields were not high. The low yield may be due to a lack of secondary matrix onto which the products can embed (such as KBr), or due to the larger size of the particles.…”

Section: Resultsmentioning

confidence: 99%

“…Oxalic acid ( Figure 68) has historically been used in uranium synthesis, including the formation of UO2 fuel, 100 formation of clusters, 101 and frameworks. 102 It is most commonly used in precipitation of uranium during fuel production.…”

Section: Oxalic Acidmentioning

confidence: 99%

“…The precipitation can form either uranium (IV) oxalate or uranyl oxalate; 103 this process is often studied by the nuclear forensics community for its effect on surface formation of the final UO2 fuel. 100 The target discussed herein is uranium (VI) oxalate, which has a different chemical structure owing to the addition of two oxygen atoms to the uranium center. Though not technically a MOF, the UO2-oxalate polymer forms stacks of 1-dimensional sheets that interact via Van der Waals interactions.…”

Section: Oxalic Acidmentioning

confidence: 99%

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Synthesis of Actinide Materials for the Study of Basic Actinide Science and Rapid Separation of Fission Products

Dorhout

2017

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This dissertation covers several distinct projects relating to the fields of nuclear forensics and basic actinide science. Post-detonation nuclear forensics, in particular, the study of fission products resulting from a nuclear device to determine device attributes and information, often depends on the comparison of fission products to a library of known ratios. The expansion of this library is imperative as technology advances. Rapid separation of fission products from a target material, without the need to dissolve the target, is an important technique to develop to improve the library and provide a means to develop samples and standards for testing separations. Several materials were studied as a proof-of-concept that fission products can be extracted from a solid target, including microparticulate (< 10 µm diameter) dUO2, porous metal organic frameworks (MOFs) synthesized from depleted uranium (dU), and other organicbased frameworks containing dU. The targets were irradiated with fast neutrons from one of two different neutron sources, contacted with dilute acids to facilitate the separation of fission products, and analyzed via gamma spectroscopy for separation yields. The results indicate that smaller particle sizes of dUO2 in contact with the secondary matrix KBr yield higher separation yields than particles without a secondary matrix. It was also discovered that using 0.1 M HNO3 as a contact acid leads to the dissolution of the target material. Lower concentrations of acid were used for future experiments. In the case of the MOFs, a larger pore size in the framework leads to higher separation yields when contacted with 0.01 M HNO3. Different types of frameworks also yield different results. The second portion of this dissertation describes efforts to better understand electronic structure and bonding of the actinide metals in various environments. One project involved studying thorium and uranium bonding with the soft-donor chalcogenides, specifically sulfur. Results from these studies include the synthesis and characterization of the novel (C5Me5)2Th(SMe)2 complex; the synthesis of (C5Me5)2ThS5 by myriad routes, indicating the product is a thermodynamic sink; and evidence that sulfur is inserted iv into the thorium-carbon bond of (C5Me5)2ThMe2 to form the pentasulfide. The second project involved unique activation of the strong carbon-halide bonds present in benzyl-halides mediated by a uranium-(2,2'-bipyridine) complex. The resultant products include a series of uranium-halide bonds from fluoride to iodide, and the addition of the benzyl group to the bipyridine ring. Studies of the mechanism indicate that the benzyl group is added first to the 6 position of the ring before migrating to its final place at the 4 position. The final project utilized a novel gold-tetrazolate complex that can be tailored to add highnitrogen ligands to actinides in a facile and safe way. This transfer ligand was used to synthesize new uranium-tetrazolate species. A brief exploration into using the transfer ligand to add tetra...

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“…Calcinations under oxygen deficient atmospheres permit to avoid over-oxidation of the final oxide. Such controlled treatments lead to actinide dioxides presenting a targeted O/M (stoichiometry of oxygen / metal) ratio close to 2.00 and usually integrating residual carbon still remaining [2,3]. Depending on the conversion conditions (heating rate / maximum temperature / atmosphere), this carbon content varies from a few ppm to about 0.42 at.…”

Section: Introductionmentioning

confidence: 99%

Speciation of residual carbon contained in UO2

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Arab-Chapelet

Tamain

et al. 2016

Journal of Solid State Chemistry

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UO 2 powders were synthesized thanks to oxalic precipitation (platelet morphology) and sol-gel route and completely characterized. A secondary phase was found in addition of the oxide depending on the calcination atmospheres. This phase has been identified by Raman spectroscopy as graphitic material (i.e. carbon-based secondary compound) and quantified by thermogravimetric analyses. Its amount varies with the calcination atmosphere. The presence of this secondary phase has no significant effect on the lattice parameter and its specific surface area.

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From uranium(IV) oxalate to sintered UO 2 : Consequences of the powders' thermal history on the microstructure

Cited by 28 publications

References 56 publications

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate

Synthesis of Actinide Materials for the Study of Basic Actinide Science and Rapid Separation of Fission Products

Speciation of residual carbon contained in UO2

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From uranium(IV) oxalate to sintered UO 2 : Consequences of the powders' thermal history on the microstructure

Cited by 28 publications

References 56 publications

Synthesis of size-controlled UO2 microspheres from the hydrothermal conversion of U(iv) aspartate

Synthesis of size-controlled UO2 microspheres from the hydrothermal conversion of U(iv) aspartate

Synthesis of Actinide Materials for the Study of Basic Actinide Science and Rapid Separation of Fission Products

Speciation of residual carbon contained in UO2

Contact Info

Product

Resources

About

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate