Thermodynamic assessment of the Na-O and Na-U-O systems: Margin to the safe operation of SFRs

Smith, Anna; Guéneau, C.; Flèche, J.-L.; Chatain, S.; Beneš, O.; Konings, R.J.M.

doi:10.1016/j.jct.2017.04.003

Cited by 11 publications

(25 citation statements)

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“…Finally, the computed thermodynamic properties of these materials together with those reported previously for rutherfordine and γ-UO 3 , were used to determine their enthalpies and free energies of formation as a function of temperature. The theoretical results obtained for rutherfordine and γ – UO 3 are shown to be in excellent agreement with experimental information.…”

Section: Discussionmentioning

confidence: 99%

“…The RWMC assigned a high priority to the critical review of relevant chemical thermodynamic data of inorganic species, actinide compounds, and fission products. , Additionally, the range of conditions (i.e., temperature and pressure) for which the thermodynamic properties are known for this kind of materials is quite limited. The temperature dependence of these properties for anhydrous uranium oxides is well-known and, therefore, thermodynamic studies have been carried out for uranium–oxygen and sodium–uranium–oxygen systems. − However, the knowledge of the corresponding information for most of uranyl containing materials, such as the secondary phases arising from alteration of spent nuclear fuel under final geological disposal is extraordinarily poor. While, most of the thermodynamic properties of these phases are known for the standard state (298.15 K and 1 bar), the almost complete absence of temperature-dependent thermodynamic data for these phases precludes the realization of accurate thermodynamic modeling studies for the study and assessment of the spent nuclear fuel geological disposal.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic Properties of Uranyl-Containing Materials Based on Density Functional Theory

et al. 2018

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermodynamic Properties of Uranyl-Containing Materials Based on Density Functional Theory

et al. 2018

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“…The lack of temperature-dependent information for these phases rules out the possibility of performing reliable thermodynamic modeling studies for the performance assessment of DGRs for SNF. 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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“…However, during an accident, the oxygen potential can increase, and therefore the reaction with metallic molybdenum (reaction ) could be expected. Note that the oxygen potential threshold for the other four mechanisms is lower than that for the formation of the trisodium uranate (Na 3 UO 4 ), which is the phase predicted to form in case of interaction between sodium and hyperstoichiometric uranium dioxide …”

Section: Resultsmentioning

confidence: 97%

“…With a procedure similar to that of Smith et al, the threshold derived for each reaction was subsequently compared to the concentration levels of oxygen dissolved in liquid sodium. Combining the oxygen solubility equation in sodium reported by Noden with the Gibbs energy of formation of Na 2 O, the oxygen potential limit in sodium is given by where C 0 is the dissolved concentration in liquid sodium.…”

Section: Resultsmentioning

confidence: 99%

Structural and Thermodynamic Investigation of the Perovskite Ba₂NaMoO_5.5

et al. 2020

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Neutron diffraction, X-ray absorption spectroscopy (XAS), and Raman spectroscopy measurements of the quaternary perovskite phase Ba2NaMoO5.5 have been performed in this work. The cubic crystal structure in space group Fm3̅m has been refined using the Rietveld method. X-ray absorption near-edge structure spectroscopy (XANES) measurements at the Mo K-edge have confirmed the hexavalent state of molybdenum. The local structure of the molybdenum octahedra has been studied in detail using extended X-ray absorption fine structure (EXAFS) spectroscopy. The Mo–O and Mo–Ba distances have been compared to the neutron diffraction data with good agreement. The coefficient of thermal expansion measured in the temperature range of 303–923 K, using high temperature X-ray diffraction (HT-XRD) (αV = 55.8 × 10–6 K), has been determined to be ∼2 times higher than that of the barium molybdates BaMoO3 and BaMoO4. Moreover, no phase transition nor melting have been observed, neither by HT-XRD nor Raman spectroscopy nor differential scanning calorimetry, up to 1473 K. Furthermore, the standard enthalpy of formation (Δf H m°) for Ba2NaMoO5.5(cr) has been determined to be −(2524.75 ± 4.15) kJ mol−1 at 298.15 K, using solution calorimetry. Finally, the margin for safe operation of sodium-cooled fast reactors (SFRs) has been assessed by calculating the threshold oxygen potential needed, in liquid sodium, to form the quaternary compound, following an interaction between irradiated mixed oxide (U,Pu)O2 fuel and sodium coolant.

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Thermodynamic assessment of the Na-O and Na-U-O systems: Margin to the safe operation of SFRs

Cited by 11 publications

References 64 publications

Thermodynamic Properties of Uranyl-Containing Materials Based on Density Functional Theory

Thermodynamic Properties of Uranyl-Containing Materials Based on Density Functional Theory

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

Structural and Thermodynamic Investigation of the Perovskite Ba₂NaMoO_5.5

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Thermodynamic assessment of the Na-O and Na-U-O systems: Margin to the safe operation of SFRs

Cited by 11 publications

References 64 publications

Thermodynamic Properties of Uranyl-Containing Materials Based on Density Functional Theory

Thermodynamic Properties of Uranyl-Containing Materials Based on Density Functional Theory

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

Structural and Thermodynamic Investigation of the Perovskite Ba2NaMoO5.5

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Structural and Thermodynamic Investigation of the Perovskite Ba₂NaMoO_5.5