Electrochemical reduction behavior of U3O8 powder in a LiCl molten salt

Jeong, Sang Mun; Shin, H. S.; Hong, Sun-Seok; Hur, Jin‐Mok; Bum, Jae; Lee, Han Soo

doi:10.1016/j.electacta.2009.10.060

Cited by 80 publications

(46 citation statements)

References 25 publications

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“…The presence of Li metal at the cathode could be observed through the potential between the cathode and Li-Pb reference electrode at an open circuit potential (i.e., the Li/Li + potential of about −0.6 V). While the constant voltage was applied, the cathode potential was lowered to about −0.78 V (Figure 3(c)) because, as a cyclic voltammetry test in our previous study showed, UO 2 is reduced at potentials more negative than −0.6 V [30,31]. A response current of about 40 A was passed by applying the constant voltage (Figure 3(b)).…”

Section: Resultsmentioning

confidence: 99%

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Quantitative Analysis of Oxygen Gas Exhausted from Anode through In Situ Measurement during Electrolytic Reduction

Choi

Lee

Heo

et al. 2017

Science and Technology of Nuclear Installations

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Quantitative analysis by in situ measurement of oxygen gas evolved from an anode was employed to monitor the progress of electrolytic reduction of simulated oxide fuel in a molten Li 2 O-LiCl salt. The electrolytic reduction of 0.6 kg of simulated oxide fuel was performed in 5 kg of 1.5 wt.% Li 2 O-LiCl molten salt at 650 ∘ C. Porous cylindrical pellets of simulated oxide fuel were used as the cathode by loading a stainless steel wire mesh cathode basket. A platinum plate was employed as the anode. The oxygen gas evolved from the anode was exhausted to the instrumentation for in situ measurement during electrolytic reduction. The instrumentation consisted of a mass flow controller, pump, wet gas meter, and oxygen gas sensor. The oxygen gas was successfully measured using the instrumentation in real time. The measured volume of the oxygen gas was comparable to the theoretically calculated volume generated by the charge applied to the simulated oxide fuel.

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Section: Resultsmentioning

confidence: 99%

“…The electrode reactions in OR processes are well known [16][17][18][27][28][29][30][31][32]. The spent oxide fuels are used as cathodes by loading them into a permeable basket.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Oxygen Gas Exhausted from Anode through In Situ Measurement during Electrolytic Reduction

Choi

Lee

Heo

et al. 2017

Science and Technology of Nuclear Installations

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“…2c) by applying a cell voltage of 3.3 V (Fig. 2a) because a cyclic voltammetry test in our previous study 40) showed that UO 2 is reduced at a potential that is more negative than −0.60 V. The Li/Li + potential measured during the interruption of the electrolysis run was −0.60 V against the Li-Pb reference electrode. The response current ranged from 7.5 to 10 A (Fig.…”

Section: Resultsmentioning

confidence: 99%

Effect of the Anode-to-Cathode Distance on the Electrochemical Reduction in a LiCl-Li₂O Molten Salt

Choi¹,

Im²,

Hur³

2013

Journal of the Korean Electrochemical Society

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: Electrochemical reductions of UO 2 at various anode-to-cathode distances (1.3, 2.3, 3.2, 3.7 and 5.8 cm) were carried out to investigate the effect of the anode-to-cathode distance on the electrochemical reduction rate. The geometry of the electrolysis cell in this study, apart from the anode-to-cathode distance, was identical for all of the electrolysis runs. Porous UO 2 pellets were electrolyzed by controlling a constant cell voltage in molten Li 2 O-LiCl at 650 o C. A steel basket containing the porous UO 2 pellets and a platinum plate were used as the cathode and anode, respectively. The metallic products were characterized by means of a thermogravimetric analyzer, an X-ray diffractometer and a scanning electron microscope. The electrolysis runs conducted during this study revealed that a short anode-to-cathode distance is advantageous to achieve a high current density and accelerate the electrochemical reduction process.

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“…134 Numerous alternative CV's of metal electrodes in LiCl-Li 2 O have also not detected any UPD current. 68,75,135 It has been demonstrated that the activity of Li in LiCl is significantly less than unity, even under Li saturated conditions. 81 This observation is highly supportive of the feasibility of Li + UPD, as it would raise the Li|Li + reduction potential.…”

Section: Before Reductionmentioning

confidence: 99%

“…66 However, research into the reduction behavior of U 3 O 8 has shown that it reacts to form lithium uranates, and reduces to UO 2 prior to reducing to metallic uranium. 44,67,68 . Furthermore, it has also been demonstrated the reduction of U 3 O 8 to UO 2 occurs spontaneously upon exposure to molten LiCl-Li 2 O.…”

Section: Experience With the Reduction Processmentioning

confidence: 99%

Review—Metallic Lithium and the Reduction of Actinide Oxides

Merwin

Williamson

Willit

et al. 2017

J. Electrochem. Soc.

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Extensive research and process development has been conducted on the electrolytic reduction of actinide oxides in molten LiCl-Li 2 O. It is now accepted that the reduction of these metal oxides occurs via two separate reduction mechanisms: direct electro-chemical reduction and mediated chemical reduction by metallic lithium. The deposition of metallic lithium at the cathode (mediated chemical reduction mechanism) during the process is known to be essential in order to achieve high process throughputs and reduction yields, and yet a knowledge gap exists regarding the nature of metallic lithium in this system. This review summarizes the formation of lithium during the process and its dispersion into the molten salt electrolyte. Previously reported aspects of the physical chemistry of the LiCl-Li 2 O-Li system are presented with a specific focus on the dispersion of Li in the solution. Finally, issues regarding the effect of the presence of lithium on the electrolytic reduction process are discussed. Evidence shows that electrochemically generated metallic lithium is likely a significant source of experimental uncertainty, low current efficiency and Li 2 O consumption in the oxide reduction process. The reduction of uranium, plutonium and minor actinide oxides to a metallic form is an important nuclear fuel cycle process.2-9 The ability of metallic lithium to reduce various uranium oxides, importantly UO 2 and U 3 O 8 , has been known for many years.10 A molten salt metalothermic reduction process employing metallic lithium (Li) as a reductant dissolved in molten LiCl was first developed by Argonne National Laboratory (ANL) to consolidate a variety of forms of actinide oxides for integration into a single electrometallurgical reprocessing system. 11-13 An electrolytic process, often referred to as electro-deoxidation or simply oxide reduction, was subsequently developed as a more controllable method of reducing metal oxides. A feasibility study conducted by Poa et al. demonstrated that oxides of uranium and plutonium could be reduced electrochemically in molten salts as long as the reduction potential of the metal oxide in question was more noble than the cation of the electrolyte.14,15 This approach was further developed by Gourishankar et al. to better understand processes chemistry and develop the electrolytic cell technology. 13,[16][17][18][19][20] Independent research conducted by Fray, Farthing, and Chen (FFC) applied the principles of electrochemical reduction in molten salt electrolytes to a variety of metal oxide reduction processes. 21,22 The FFC process has been the subject of several literature reviews.23-25 While these review articles address the processes associated with the reduction of nuclear fuel in LiCl, they focus on the electro-deoxidation phenomena and the CaCl 2 -CaO system. Additionally, the process engineering of the electrolytic reduction of nuclear fuel, and experience in incorporating oxide fuel into pyroprocessing, has been the focus of a recent review article. 26 The current review wi...

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Electrochemical reduction behavior of U3O8 powder in a LiCl molten salt

Cited by 80 publications

References 25 publications

Quantitative Analysis of Oxygen Gas Exhausted from Anode through In Situ Measurement during Electrolytic Reduction

Quantitative Analysis of Oxygen Gas Exhausted from Anode through In Situ Measurement during Electrolytic Reduction

Effect of the Anode-to-Cathode Distance on the Electrochemical Reduction in a LiCl-Li₂O Molten Salt

Review—Metallic Lithium and the Reduction of Actinide Oxides

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Electrochemical reduction behavior of U3O8 powder in a LiCl molten salt

Cited by 80 publications

References 25 publications

Quantitative Analysis of Oxygen Gas Exhausted from Anode through In Situ Measurement during Electrolytic Reduction

Quantitative Analysis of Oxygen Gas Exhausted from Anode through In Situ Measurement during Electrolytic Reduction

Effect of the Anode-to-Cathode Distance on the Electrochemical Reduction in a LiCl-Li2O Molten Salt

Review—Metallic Lithium and the Reduction of Actinide Oxides

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Effect of the Anode-to-Cathode Distance on the Electrochemical Reduction in a LiCl-Li₂O Molten Salt