Uranium (III) precipitation in molten chloride by wet argon sparging

Vigier, Jean-François; Laplace, Annabelle; Renard, Catherine; Miguirditchian, Manuel; Abraham, Francis

doi:10.1016/j.jnucmat.2016.03.005

Cited by 17 publications

(9 citation statements)

References 28 publications

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“…Uranium can exhibit multiple oxidation states within a salt melt. These include U(III) and U(IV), which are standard target states maintained in MSRs or pyroprocessing schemes; however, U can also take on the U(VI) state. , Furthermore, U speciation can be highly complex, presenting both dissolved or precipitated species , and intricate complexes when other metals or impurities are present in the salt. , All of these factors impact optical fingerprints and can lead to highly complex signals. This section provides a general overview of fingerprints to enable a better understanding of the dynamic behavior demonstrated in the following sections.…”

Section: Resultsmentioning

confidence: 99%

“…These include U(III) and U(IV), which are standard target states maintained in MSRs or pyroprocessing schemes; 35 however, U can also take on the U(VI) state. 36,37 Furthermore, U speciation can be highly complex, presenting both dissolved or precipitated species 38,39 and intricate complexes when other metals or impurities are present in the salt. 40,41 All of these factors impact optical fingerprints and can lead to highly complex signals.…”

Section: ■ Introductionmentioning

confidence: 99%

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Exploring the Complex Chemistry of Uranium within Molten Chloride Salts

Branch,

Felmy,

Schafer Medina

et al. 2023

Ind. Eng. Chem. Res.

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Harsh environments represent a unique opportunity to explore new frontiers in chemistry while developing novel tools to meet global needs. Exploring the chemistry of uranium within molten salts is a key example. Actinide chemistry within the highly ionic environment of a molten salt is poorly understood, particularly in the presence of common salt impurities or without active oxidation state control. Delving into this chemistry can provide new insight into actinide and f-electron interactions. Furthermore, expanding our chemical knowledge can also enable advances in the deployment of molten salt reactors or molten salt recycle schemes. Both molten salt applications aim toward providing green and reliable energy as well as critical materials for the world. Here, the utilization of visible absorbance and Raman spectroscopies to understand and quantify U within chloride-based salt eutectics is discussed. Furthermore, machine learning techniques in the form of chemometric modeling are developed and described, providing advanced analytical tools to quantify and characterize the U present. These tools are then leveraged to monitor and explore the dynamic fundamental chemistry of U within chloride-based salt melts without active oxidation state control.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Exploring the Complex Chemistry of Uranium within Molten Chloride Salts

Branch,

Felmy,

Schafer Medina

et al. 2023

Ind. Eng. Chem. Res.

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“…These results demonstrate that uranium and lanthanides react independently with Li 2 O in the LiCl-KCl melt, and concentration control of the oxide ion can separate uranium from a chloride molten salt containing several lanthanide ions. 18 In addition, the electrochemical measurement tool used in this study has potential for on-line monitoring of the chemical reactions in the melt. 9…”

Section: Resultsmentioning

confidence: 99%

“…Several research groups have studied such reactions by potentiometric titration of the oxide ion in the melt and product characterization, in order to estimate the thermodynamic properties for oxide reduction 10,[12][13][14][15] and to partition lanthanides and actinides from the melt. 11,[16][17][18] In the present work, we focused monitoring the chemical behaviors of ions of interest (U 3+ , Nd 3+ , Ce 3+ , and La 3+ ) in situ during their reactions with O 2− in the LiCl-KCl molten salt by means of electrochemical and spectroscopic tools. The chronological cyclic voltammograms (CVs) and absorption spectra elucidated the chemical reactions of the actinide/lanthanide and oxide ions, in combination with the characterization of the precipitates using Raman spectroscopy and Xray diffraction (XRD) analysis.…”

mentioning

confidence: 99%

Electrochemical and Spectroscopic Monitoring of Interactions of Oxide Ion with U (III) and Ln (III) (Ln = Nd, Ce, and La) in LiCl-KCl Melts

Choi

Bae

Park

2017

J. Electrochem. Soc.

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Using cyclic voltammetry and UV-vis absorption spectroscopic methods, we studied the precipitation reactions of trivalent uranium and lanthanides (Nd, Ce, and La) with the oxide ion in LiCl-KCl molten salts, which are likely side reactions during the electrorefining process for nuclear fuel treatment. The in situ electrochemical and spectroscopic monitoring demonstrated that U 3+ consumed O 2− with the mole ratio of 2:1, whereas the lanthanide ions reacted with O 2− with the mole ratio of 1:1. Raman spectroscopy and X-ray diffraction were also employed to analyze the precipitates, confirming that U 3+ was precipitated and oxidized into UO 2 , while the trivalent lanthanide ions formed oxychlorides (LnOCl). As a preliminary study of actinide co-precipitation, we also electrochemically monitored the precipitation reactions in a mixed melt containing uranium and lanthanides, demonstrating a higher reactivity of the former with the oxide ion in LiCl-KCl. Understanding the chemical reactions in chloride-based molten salts at high temperatures is of fundamental importance for developing pyroprocessing technologies, which have been extensively examined over the last 30 years as a promising solution for accumulated spent nuclear fuel. [1][2][3][4] In particular, the electrochemical behaviors of actinides and lanthanides in LiCl-KCl melts have been widely studied to explain the fundamental electrochemical reactions in the electrorefining process, which partitions reusable metals and highly radioactive fission products.5-7 However, before the commercialization of this technology, it is necessary to obtain comprehensive insight of the molten salt chemistry of trace elements dissolved from the spent nuclear fuel, and the additives and/or impurities that enter during the process. 8,9 Li 2 O is a critical ingredient for the electrochemical reduction of spent oxide fuel. It affords O 2− ions that should diffuse to the anode at the beginning of the reduction process, and controls the O 2− concentration in the LiCl melt to prevent the Pt cathode from dissolving. 3 However, a trace amount of Li 2 O likely remains in the reduced fuel, even after distilling out the molten salt at the end of the oxide reduction process, and can enter the next process. During the electrorefining process, the oxide ion may react with trivalent actinide and lanthanide ions in the LiCl-KCl eutectic melt, affording insoluble oxides and oxychlorides 10,11 which contaminate the salt and reduce the purity and yields of recovered uranium. In addition, unreduced lanthanide oxides in the metal fuel feed play the role of oxo-donor in the LiClKCl melt.12 Therefore, knowledge of the reactions between the actinide/lanthanide ions and the oxide ion in the molten salt could lead to improvement in the electrorefining technology. Several research groups have studied such reactions by potentiometric titration of the oxide ion in the melt and product characterization, in order to estimate the thermodynamic properties for oxide reduction 10,12-15 and to partition lanthan...

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“…Para el mecanismo de precipitación con la solución de NaF se obtuvieron las condiciones de concentración óptimas para las cuales el porcentaje de uranio en la solución es menor, siendo concentración de la solución del NaF 0,5M, tiempo de contacto 12 hrs y sin agitación generando un compuesto insoluble como es el NaUF 6 . Otros trabajos estudiados como es VIGIER et al [5] utilizan condiciones redox y altas temperaturas, pero los costos y las variables operativas del proceso de precipitación aumentan considerablemente.…”

Section: Discusionesunclassified

Precipitación de uranio a partir de licores alcalinos

et al. 2018

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RESUMEN En Argentina existen minerales de uranio con abundante contenido de materia orgánica, conjuntamente variedad en cantidad de sulfuros y carbonatos que actúan como cemento o sellando diaclasas. Estos últimos minerales, modifican directamente la elección del proceso metalúrgico de lixiviación para la concentración de uranio. El proceso seleccionado más benéfico, resulta ser la lixiviación alcalina. Una vez realizada la lixiviación alcalina del mineral de uranio, mediante el uso del agente lixiviante como es el Na2CO3/NaHCO3 en presencia de agente oxidantes, se logra llegar al estado hexavalente del uranio como U3O8. En este trabajo de investigación se plantea el diseño experimental a nivel de laboratorio, con el fin de obtener la precipitación de uranio a partir de licores de lixiviación alcalina mediante dos mecanismos diferentes de precipitación. El primero utiliza un agentes oxidantes fuertes como el peróxido de hidrogeno en exceso. Estequiométricamente, se utilizó 0,9 g de H2O2, obteniendo la precipitación de uranio como UO2*2H2O. Las variables de trabajo son condiciones de pH débilmente ácidas, para valores comprendidos entre 2.5, 4 hasta 5 y tiempos de reacción con exposición del mineral de 1, 2, 3 y 4 hrs. Las temperaturas de trabajo son de 25 ºC, 60 ºC y 80 ºC para una velocidad de agitación constante de 400 rpm. En el segundo mecanismo se adiciona un agente precipitante como es el NaF en medio alcalino, sin modificación del pH de los licores lixiviados, generando un compuesto insoluble como es el NaUF6. Para ello se trabajó con distintas concentraciones del agente precipitante, velocidad de agitación y tiempos de precipitación. Sin embargo el mecanismo de mejor repuesta fue el primero, donde los valores de recuperación de uranio óptimos fueron encontrados para condiciones de trabajo de pH: 2,5; temperatura de 60 ºC y tiempos de reacción superiores a 3 h hasta 4 h.

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Uranium (III) precipitation in molten chloride by wet argon sparging

Cited by 17 publications

References 28 publications

Exploring the Complex Chemistry of Uranium within Molten Chloride Salts

Exploring the Complex Chemistry of Uranium within Molten Chloride Salts

Electrochemical and Spectroscopic Monitoring of Interactions of Oxide Ion with U (III) and Ln (III) (Ln = Nd, Ce, and La) in LiCl-KCl Melts

Precipitación de uranio a partir de licores alcalinos

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