Oxidation behaviour of uranium and neptunium in stabilised zirconia

Walter, Marcus; Somers, J.; Bouëxière, Daniel; Gaczyński, P.; Brendebach, Boris

doi:10.1016/j.jssc.2009.09.022

Cited by 12 publications

(4 citation statements)

References 33 publications

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“…Both Fe(II) and Fe(III) occupy the octahedral sites in the magnetite inverse spinel structure, but substitution of U into the structure is likely to preferentially replace Fe(III) to aid charge balance. Indeed, the observed expansion of the site occurs in a similar way to other instances of metal incorporation (Dardenne et al, 2002;Walter et al, 2009). The presence of the shoulder on the rising edge in the XANES spectrum is not inconsistent with U(V) in the OCL reduced sample.…”

Section: X-ray Absorption Spectroscopysupporting

confidence: 61%

Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste

et al. 2015

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Uranium incorporation into magnetite and its behaviour during subsequent oxidation has been investigated at high pH to determine the uranium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to U(VI) aq containing cement leachates ( pH 10.5-13.1) and crystallization of magnetite was induced via addition of Fe(II) aq . A combination of XRD, chemical extraction and XAS techniques provided direct evidence that U(VI) was reduced and incorporated into the magnetite structure, possibly as U(V), with a significant fraction recalcitrant to oxidative remobilization. Immobilization of U(VI) by reduction and incorporation into magnetite at high pH, and with significant stability upon reoxidation, has clear and important implications for limiting uranium migration in geological disposal of radioactive wastes.

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Section: X-ray Absorption Spectroscopysupporting

confidence: 61%

Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste

et al. 2015

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“…It is useful to construct the relationship of oxygen potential‐temperature‐composition and further optimize the sintering conditions of this novel nuclear fuel. Walter et al revealed the oxidation behavior of uranium in yttria stabilized zirconia. Under reducing conditions, the oxidation state of the uranium was +4 in the obtained fluorite‐type structure, (Zr,Y,U)O 2‐x .…”

Section: Applications Of Xanes In Actinide Characterizationmentioning

confidence: 99%

Exploring Actinide Materials Through Synchrotron Radiation Techniques

et al. 2014

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Synchrotron radiation (SR) based techniques have been utilized with increasing frequency in the past decade to explore the brilliant and challenging sciences of actinide‐based materials. This trend is partially driven by the basic needs for multi‐scale actinide speciation and bonding information and also the realistic needs for nuclear energy research. In this review, recent research progresses on actinide related materials by means of various SR techniques were selectively highlighted and summarized, with the emphasis on X‐ray absorption spectroscopy, X‐ray diffraction and scattering spectroscopy, which are powerful tools to characterize actinide materials. In addition, advanced SR techniques for exploring future advanced nuclear fuel cycles dealing with actinides are illustrated as well.

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“…Furthermore, XAS is a suitable method to assess supplementary data since it allows obtaining atomic local environment and information on cation valence state. XAS is a powerful analytical tool for the characterization of actinide oxides. − For the specific case of americium bearing materials, XAS studies are limited to AmO 2 , , (Zr,Y,Am)O 2 , ,, AmAlO 3 , Pb 2 Se 2 AmCu 3 O 8 , and Am(OH) 3 …”

Section: Introductionmentioning

confidence: 99%

Local Structure and Charge Distribution in Mixed Uranium–Americium Oxides: Effects of Oxygen Potential and Am Content

et al. 2011

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Partitioning and transmutation (P&T) of minor actinides (MA) is currently studied to reduce the nuclear waste inventory. In this context, the fabrication of MA bearing materials is of great interest to achieve an effective recycling of these highly radioactive elements. To ensure the in-pile behavior, nuclear oxide fuels have to respect several criteria including preservation of the fluorite structure and defined oxygen to metal ratio (O/M). In the case of Am bearing materials, such as U(1-y)Am(y)O(2±x) (y = 0.10, 0.15, 0.20), the O/M determination is quite challenging using conventional methods (TGA, XRD) because of the particular thermodynamic properties of Am. Despite the lack of experimental data in the U-Am-O system, thermodynamical models are currently developed to effectively assess the O/M ratio. In this work, the O/M ratios were calculated for various oxygen potentials using the cation molar fraction determined by XAS measurements. These results are an important addition to the experimental data available for the U-Am-O system. Moreover, XRD and XAS indicated that the fabrication of fluorite U(1-y)Am(y)O(2±x) solid solution was achieved for all Am content and oxygen potentials investigated. On the basis of the molar fraction, a description of the solid solution was proposed depending on the considered sintering conditions. Finally, the occurrence of an unexpected charge compensation mechanism was pointed out.

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Oxidation behaviour of uranium and neptunium in stabilised zirconia

Cited by 12 publications

References 33 publications

Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste

Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste

Exploring Actinide Materials Through Synchrotron Radiation Techniques

Local Structure and Charge Distribution in Mixed Uranium–Americium Oxides: Effects of Oxygen Potential and Am Content

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