Electrochemical properties of the Ag+|Ag and other reference electrodes in the LiCl–KCl eutectic melts

Shirai, Osamu; Nagai, Takayuki; Uehara, Akihiro; Yamana, Hideaki

doi:10.1016/j.jallcom.2007.02.104

Cited by 43 publications

(34 citation statements)

References 16 publications

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“…Initially, a silver-silver ion (Ag/Ag + ) electrode (1 wt% Ag in LiCl-KCl) contained within a thinned, closed-end Vycor glass tube was used as the reference electrode for the measurements. 31,32 However, the durability of the Vycor glass at elevated temperature is poor and its lifetime is very short. Replacing the closed-end Vycor tube with a closed-end mullite tube improved the durability of the electrode but introduced additional redox peaks in the voltammograms, presumably caused by formation of salt-soluble species arising from a reaction between mullite and trivalent actinide ions in molten salt.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Tylka¹,

Willit²,

Williamson³

2017

J. Electrochem. Soc.

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This work examines the nucleation and growth behavior of uranium and plutonium from molten LiCl-KCl eutectic on inert electrodes using electrochemical techniques. Current-time transients obtained from chronoamperometric experiments were compared with theoretical models to characterize the type of nucleation (progressive or instantaneous) for deposition of U and Pu, and co-deposition of U-Pu, from molten LiCl-KCl at inert electrodes. It was established that the nucleation mode of actinides present as chlorides in molten chloride salts changes from progressive to instantaneous with an increasing concentration of the trivalent actinide ions in the salt. The effect of the material of the working electrode was investigated, and it was found that changing the material from tungsten to silver improves resolvability of the nucleation peaks and allows more accurate analysis of the experimental measurements. Using the nucleation data, diffusion coefficients were obtained for U 3+ and Pu 3+ , and were found to be in very good agreement with the values obtained from other studies. The density of nuclei produced during instantaneous nucleation, the rate of nucleation for progressive nucleation, and the radius of the deposited nuclei were evaluated and examined at different overpotentials. Pyrochemical reprocessing technology represents a promising alternative to aqueous processes for separating actinides from irradiated fuel by applying electrolytic methods to the molten salt media. [1][2][3][4][5][6][7] Electrorefining is the main step in pyrochemical reprocessing. During this process, actinides are separated from the bulk of the fission product elements by electrotransport onto a solid or liquid cathode. Electrochemical deposition that takes place at the electrode/electrolyte interface occurs by a process of nucleation and growth and is strongly dependent on the overpotential. [8][9][10][11] Nuclei initially form at active sites of the substrate, consistent with some nucleation rate law, and then grow via the incorporation of additional ions from the electrolyte. Determination of the fundamental parameters of the nucleation and growth phenomena and a very good physical understanding of these processes are essential for improved control and efficiency of pyroprocesses.Electrochemical methods are widely used to study nucleation and growth phenomena in aqueous or molten media because the driving force of nucleation can be easily changed by varying the applied potential.12 Chronoamperometry (CA) is the most frequently used technique for quantitative analysis of the deposition process; it entails applying potential step pulses and observing the resulting currenttime transients. Immediately after applying the potential step, there is a decreasing current transient corresponding to the charging of the double layer, followed by a current due to the formation of the new phase, and an increase in the number of nuclei. As the nuclei grow, the coalescence of adjacent diffusion zones gives rise to a current maximum, followed by a decay...

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Section: Methodsmentioning

confidence: 99%

Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Tylka¹,

Willit²,

Williamson³

2017

J. Electrochem. Soc.

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“…Results of this work will be presented against both the Ag|AgCl and Cl -|Cl 2 scales. Conversion from the 5 mol% Ag|AgCl scale to the Cl -|Cl 2 scale can be performed in the following manner, as demonstrated by Shirai [15].…”

Section: Reference Electrodementioning

confidence: 99%

Thermal Properties of LiCl-KCl Molten Salt for Nuclear Waste Separation

Sridharan

Allen

Anderson

et al. 2012

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“…There are quite a few conversion equations available in the literature. 6,14,15 For the determination of the activity of the analyte using an analyte reference electrode, this conversion is not necessary. Additionally the error contributions due to lack of knowledge of the activity coefficient of AgCl in the reference electrode is also eliminated.…”

Section: Journal Of the Electrochemical Society 164 (8) H5299-h5307 mentioning

confidence: 99%

Activity Measurements of Gadolinium(III) Chloride in Molten LiCl-KCl Eutectic Salt Using Saturated Gd/GdCl₃Reference Electrode

Bagri

Simpson

2017

J. Electrochem. Soc.

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The activity coefficients of rare earth chlorides in molten salt systems are of great interest for the research, development and commercialization of pyrochemical processing of spent nuclear fuels. In this paper, the activity coefficient of GdCl 3 in molten LiCl-KCl eutectic salt has been studied using a two electrode electrochemical cell with a gadolinium metal rod as working electrode and a saturated Gd|GdCl 3 -LiCl-KCl reference electrode. Use of this analyte reference electrode allows for the elimination of hereto unavoidable errors in the experiments. It is determined that the activity coefficient of GdCl 3 is a function of concentration; decreasing from 3.9 × 10 −4 at low concentrations to 4.9 × 10 −5 at about 0.62 mol % GdCl 3 , remaining unchanged up to about 2 mol % GdCl 3 after which it begins to increase with increasing concentration of GdCl 3 . Further it is also determined experimentally that presence of high levels of CsCl tends to decrease the activity coefficient of The pyrochemical processing (pyroprocessing) of spent nuclear fuel and the development of high temperature separations process technology is one of the flowsheet options for closing the spent fuel cycle. During pyrochemical separations, it is proposed that the uranium and transuranic species are selectively separated from the spent fuel in a high temperature electrorefining process. LiCl-KCl eutectic salt serves as the electrolyte for the electrorefining cell. A stainless steel basket, in which spent fuel is placed, serves as the anode. The cathode can be an inert metal (steel), a reactive metal (aluminum) or liquid metal cathode (cadmium). Inert solid cathodes are excellent at recovering pure uranium deposits, 1 reactive solid metal cathodes are good at collecting uranium and transuranic elements with less rare earth impurities 2 whereas liquid metal cathodes allow for the co-deposition of uranium and transuranic elements during the electrorefining process but can result in high levels of rare earth impurities in the cathode deposit.3 Actinide drawdown process can be used to achieve high levels of actinide recovery from the salt prior to disposal. In theory, actinides are electrochemically more noble (more positive standard reduction potentials) than the rare earths and other fission products present in the molten salt hence can be selectively reduced on the cathode. Standard reduction potentials (E 0 ) does not account for the deviation from ideal behavior both the actinides and rare earths are reported to exhibit in the molten salt systems. This deviation can be quantified using the activity coefficients of the species.The motivation for future research and development of the nuclear fuel cycle is both efficient utilization of the fuel as well as waste minimization. After an actinide recovery step, the actinide-free, fission product-rich salt will need to be disposed safely after immobilizing the salt in waste forms suitable for long term storage in a deep geological repository. Recently, flowsheets were proposed for the further re...

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Electrochemical properties of the Ag+|Ag and other reference electrodes in the LiCl–KCl eutectic melts

Cited by 43 publications

References 16 publications

Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Thermal Properties of LiCl-KCl Molten Salt for Nuclear Waste Separation

Activity Measurements of Gadolinium(III) Chloride in Molten LiCl-KCl Eutectic Salt Using Saturated Gd/GdCl₃Reference Electrode

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Electrochemical properties of the Ag+|Ag and other reference electrodes in the LiCl–KCl eutectic melts

Cited by 43 publications

References 16 publications

Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Thermal Properties of LiCl-KCl Molten Salt for Nuclear Waste Separation

Activity Measurements of Gadolinium(III) Chloride in Molten LiCl-KCl Eutectic Salt Using Saturated Gd/GdCl3Reference Electrode

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Activity Measurements of Gadolinium(III) Chloride in Molten LiCl-KCl Eutectic Salt Using Saturated Gd/GdCl₃Reference Electrode