Identification, measurement, and mitigation of key impurities in LiCl-Li2O used for direct electrolytic reduction of UO2

Gonzalez, Mario Alberto; Burak, Adam; Guo, Shaoqiang; Simpson, Michael F.

doi:10.1016/j.jnucmat.2018.08.020

Cited by 21 publications

(8 citation statements)

References 23 publications

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“…The improper drying of LiCl can lead to the formation of LiOH, which can decrease the efficiency of the DOER process. 34 As-received Li 2 O was further dried under vacuum at 900 °C for 3 h. Vacuum dried Li 2 O (∼4.2 g) was added to anhydrous LiCl inside the glove box for the preparation of LiCl-1 wt% Li 2 O melt.…”

Section: Methodsmentioning

confidence: 99%

Preparation of U-Nb alloy from oxide precursors by direct oxide electrochemical reduction method

Khan¹,

Mukherjee²,

Kumaresan³

2022

J. Electrochem. Soc.

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The aim of the present study was to prepare U-7 wt.% Nb alloy by the direct oxide electrochemical reduction method. The alloy was prepared from the mixed oxide precursors namely, UO2 and Nb2O5. When the precursors were sintered in a reducing atmosphere of Ar-8 vol.% H2, Nb2O5 was converted into NbO2. Subsequently, the mixed oxide pellet (UO2-NbO2) was reduced by the lithium metal, electrochemically generated from a molten LiCl-1 wt.% Li2O bath at 700°C. The electro-lithiothermic reduction was performed by constant current electrolysis mode with a mixed oxide pellet as the cathode and platinum as the anode. The reduction pathways of the individual oxides and the mixture were established using cyclic voltammetry and potentiostatic electrolysis techniques. The reduced alloy was characterized by X-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). These results confirmed the formation of U-Nb alloy. The composition of the alloy was determined by EDS, energy-dispersive X-ray fluorescence and chemical analysis.

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Section: Methodsmentioning

confidence: 99%

Preparation of U-Nb alloy from oxide precursors by direct oxide electrochemical reduction method

Khan¹,

Mukherjee²,

Kumaresan³

2022

J. Electrochem. Soc.

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“…Electrolyte preparation.-LiCl (99.5 wt%, FMC, UK) and Li 2 O were used for the electrolyte preparation. To eliminate an impurities (LiOH, Li 2 CO 3 et al 23 ) LiCl was gradually heated under vacuum, melted in argon atmosphere, and purified by the zone recrystallization. [24][25][26] The required amount of Li 2 O was immersed into the electrolyte as a pre-saturated LiCl-Li 2 O melt.…”

Section: Methodsmentioning

confidence: 99%

Reduction of ZrO₂ in LiCl-Li₂O Melt During Electrolysis

Shishkin¹,

Shishkin²,

Nikolaev³

et al. 2022

J. Electrochem. Soc.

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Reduction of spent nuclear fuel (SNF) components to metals during the electrolysis of the LiCl-Li2O melt at 650°C is extremely important in the framework of the development of fuel reprocessing technology. Here, ZrO2 reduction by lithium during the electrolysis of the LiCl-Li2O melt at 650°C was studied. Cathode processes on a molybdenum substrate in contact with different ZrO2 samples (powder, pressed pellet, dense ceramic) were analyzed using cyclic voltammetry and electrolysis. It was shown that the appearance of ZrO2 near the molybdenum cathode leads to increasing cathode currents and decreasing lithium oxidation current. Both effects indicate the consumption of reduced lithium for the reduction of ZrO2 samples. In order to analyze the reduction products X-ray phase analysis and scanning electron microscopy were used, and to estimate the reduction degree of ZrO2 samples three methods were tested: dissolution of samples in inorganic acid solution, dissolution of samples in EtOAc/Br2 solution, and carbothermal reduction. It was shown that during the electrolysis of dense samples only the lithium zirconate (Li2ZrO3) was formed at their surfaces, whereas the electrolysis of ZrO2 powder samples resulted in the formation of Li2ZrO3, Zr3O, and ZrO phases.

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“…While hydrolysis was not explicitly shown to be the cause of impurity formation in work done by Gonzalez et al, the study was motivated to determine the cause of unexpected cathodic reactions preceding UO2 and Li2O reduction during direct electrolytic reduction (DER) in LiCl-Li2O, as shown in work published by Herrmann et al (1,2). In the work published by Herrmann et al, a broad cathodic current began to develop at -1.0 V vs Ni/NiO as Li2O was added to the salt (2).…”

Section: Studies With Molten Liclmentioning

confidence: 99%

“…The magnitude of the cathodic current increased as larger quantities of Li2O were added. Due to the hygroscopic nature of LiCl, Gonzalez et al suspected that moisture-induced contamination could be the cause of this prereduction current; resulting in the formation of LiOH as residual moisture is expected was interact with LiCl or Li2O as shown in Equations [1] and [2] (1).…”

Section: Studies With Molten Liclmentioning

confidence: 99%

Electrochemical Methods for Analysis of Hydroxide and Oxide Impurities in Li, Mg/Na, and Ca Based Molten Chloride Salts

Gonzalez¹,

Faulkner²,

Zhang³

et al. 2020

ECS Trans.

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Due to their highly hygroscopic nature, molten chloride salts are known to resist complete thermal dehydration, resulting in incomplete water removal prior to use in high temperature applications. At temperatures required to melt these salts, this can result in hydrolysis, leading to formation of oxides or hydroxides. Depending on application, these hydrolytic impurities can cause further adverse effects through the formation of insoluble oxides and oxychlorides. In this paper, previously published work is reviewed to discuss electrochemical methods used for identification and measurement of hydrolytic impurities in LiCl and CaCl2 as well as their effect on electrolytic processes. Cyclic voltammetry shows that thermal dehydration of LiCl and CaCl2 promotes LiOH and CaO formation, respectively. The presence of CaO in a CaCl2-CeCl3 salt meant to emulate a typical actinide-chloride electrorefining salt causes insoluble Ce2O3 and CeClO to form, reducing electrochemical signals as the active species is precipitated as an insoluble phase.

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Identification, measurement, and mitigation of key impurities in LiCl-Li2O used for direct electrolytic reduction of UO2

Cited by 21 publications

References 23 publications

Preparation of U-Nb alloy from oxide precursors by direct oxide electrochemical reduction method

Preparation of U-Nb alloy from oxide precursors by direct oxide electrochemical reduction method

Reduction of ZrO₂ in LiCl-Li₂O Melt During Electrolysis

Electrochemical Methods for Analysis of Hydroxide and Oxide Impurities in Li, Mg/Na, and Ca Based Molten Chloride Salts

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Identification, measurement, and mitigation of key impurities in LiCl-Li2O used for direct electrolytic reduction of UO2

Cited by 21 publications

References 23 publications

Preparation of U-Nb alloy from oxide precursors by direct oxide electrochemical reduction method

Preparation of U-Nb alloy from oxide precursors by direct oxide electrochemical reduction method

Reduction of ZrO2 in LiCl-Li2O Melt During Electrolysis

Electrochemical Methods for Analysis of Hydroxide and Oxide Impurities in Li, Mg/Na, and Ca Based Molten Chloride Salts

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Reduction of ZrO₂ in LiCl-Li₂O Melt During Electrolysis