Electrochemical behaviour of gadolinium ion in molten LiCl–KCl eutectic

Caravaca, C.; Córdoba, G. De; Tomás, Miguel; Rosado, M.

doi:10.1016/j.jnucmat.2006.08.009

Cited by 59 publications

(58 citation statements)

References 24 publications

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“…In most of the studies, measurements have been made simply by visual determination of the immersion depth, 4,14,17,[22][23][24][25][26][27][28]32,33,39,42,[49][50][51][52][53]58 which has an error associated with capillary effects and wetting between the electrode and the salt at different temperatures. Several studies used wires encased in alumina or other insulating material tubes with a known apparent surface area.…”

Section: Resultsmentioning

confidence: 99%

Method Development for Quantitative Analysis of Actinides in Molten Salts

Tylka

Willit

Prakash

et al. 2015

J. Electrochem. Soc.

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This paper describes how electrochemical techniques have been used to develop a method for high-precision, real-time quantitative measurements of the concentration of actinides, present in in molten salts as actinide chlorides, for pyrochemical process monitoring applications. Possible reasons for discrepancies between reported measurements obtained with electrochemical techniques have been investigated and a combination of methods to improve their precision has been established. The combination of methods consists of selecting a suitable electroanalytical measurement technique, experimentally verifying assumptions used in its theoretical analysis, ensuring reproducible conditions at the electrode/electrolyte interface, and using an improved method to eliminate the need to know the electrode surface area. By following the developed procedures and refining both experimental techniques and data analysis methods, precise and reproducible measurements were obtained for U and Pu in LiCl/KCl eutectic at 773 K. Preliminary results showed that cyclic voltammetry, along with a method of standard area addition, are very promising tools for in situ quantitative measurements with a degree of precision comparable to destructive analysis techniques. Electrorefining is the main step in pyrochemical reprocessing. During this process, actinides are separated from the bulk of the fission product elements by electrochemical dissolution and electrotransport onto a solid or liquid cathode. The goal of the process is to maximize the separation and recovery of actinides from chlorinated fission products so that minimal amounts of actinides are lost to the process waste stream. [1][2][3][4][5] In addition to efficient actinide recovery, there is a need to address the safeguarding the recycle system. 5 Highprecision, real-time concentration measurements of actinides, present as actinide chlorides, in molten salts are required for process monitoring and control and could be used to support traditional material control and accountability techniques. Development of these measurements is essential to implement and operate a commercial fuel reprocessing facility. [6][7][8][9][10] Electrochemical techniques are well suited for in situ monitoring because they allow rapid, real-time measurements, are compatible with remote handling operations, and do not require the use of standards. Also, the equipment is not affected by the high radiation field present in a fuel processing operation.9,10 Unlike offline destructive analysis techniques, in situ methods do not require representative sample collection and preparation, and therefore avoid problems with sample contamination and degradation. In addition, analytical results can be received in a relatively short period (for example, less than 2 minutes).In an electrochemical cell, the measured potential (E), current (i), or charge (Q) is related to the quantity of the analyte in the solution; therefore, it can serve as an analytical signal for concentration measurements. 11,12 Depending on the applied...

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Section: Resultsmentioning

confidence: 99%

Method Development for Quantitative Analysis of Actinides in Molten Salts

Tylka

Willit

Prakash

et al. 2015

J. Electrochem. Soc.

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“…[5][6][7] It is important to note that all of these authors used different electrochemical cell set-up than the one presented here for their experimental measurements. Tang and Pesic 5 and Caravaca et al 7 both used Ag/AgCl reference electrode for their experimental measurements. Lantelme and Berghoute 6 used a standard Cl − /Cl 2 reference electrode for their measurements.…”

Section: Effect Of Gdclmentioning

confidence: 99%

“…At the closest comparable concentration of 1.49 wt % GdCl 3 at 773 K, this work reports an activity coefficient value of 5.312 × 10 −5 . Caravaca et al 7 reported the activity coefficient of GdCl 3 at a single concentration of 1.66 × 10 −3 mole fraction at 773 K. They reported two values of the activity coefficient; 4.60 × 10 −3 and 1.50 × 10 −4 . The reason for the two significantly different values reported by Caravaca et al 7 was the use of two different standard states by them for their calculations.…”

Section: Effect Of Gdclmentioning

confidence: 99%

“…Caravaca et al 7 reported the activity coefficient of gadolinium chloride in LiCl-KCl eutectic salt at a single concentration of 0.166 mol % GdCl 3 . Caravaca et al 7 in calculating their activity coefficients used two different standard states for their calculations reporting two vastly different activity coefficient values for the same concentration of gadolinium chloride. Lantelme and Berghoute 6 determined the activity coefficient as a function of concentration up to 1.44 mol % GdCl 3 .…”

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confidence: 99%

“…Lantelme and Berghoute 6 for their work used a definition of standard state with unit activity at infinite dilution and reported activity coefficients of GdCl 3 that are vastly different from the other two studies cited here. 5,7 From the data reported in the three main studies cited here, two key areas remain with substantial knowledge gaps. First expanding the concentration range and exploring the concentration dependence of the activity coefficient of GdCl 3 above and beyond the 1.44 mol % GdCl 3 reported in the single study by Lantelme and Berghoute.…”

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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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Capillary Imbibition of Gadolinium Halides into WS₂ Nanotubes: a Molecular Dynamics View

Deepak

Enyashin

2016

Israel Journal of Chemistry

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The structure of the molten salts GdX3, where X denotes Cl, Br, or I, and the kinetics of their penetration into WS2 nanotubes were investigated using molecular dynamics simulations. The GdCl3 and GdBr3 melts are found to comprise an amorphous framework structure with substantial intermediate‐range ordering, as manifested by pair distribution, and angle‐resolved pair‐pair distribution functions associated with cationic correlations. In contrast, the GdI3 melt is a liquid with short‐range cationic ordering. These structural peculiarities cause dramatically different mobility of Gd cations among pure GdX3 melts and explain the relative difference in the capillary activity of WS2 nanotubes regarding the melts, as observed in preliminary experiments. Extended MD simulations of GdCl3 dissolved in molten KCl predict the total degradation of the GdCl3 framework structure below 40 mol %, although no essential uptake of Gd cations by the WS2 nanotube is observed, due to more progressive diffusion of K cations. Our theory suggests that, among the considered halides, only the GdI3 compound is suitable for Gd encapsulation into WS2 nanotubes employing the capillary technique.

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Electrochemical behaviour of gadolinium ion in molten LiCl–KCl eutectic

Cited by 59 publications

References 24 publications

Method Development for Quantitative Analysis of Actinides in Molten Salts

Method Development for Quantitative Analysis of Actinides in Molten Salts

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

Capillary Imbibition of Gadolinium Halides into WS₂ Nanotubes: a Molecular Dynamics View

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Electrochemical behaviour of gadolinium ion in molten LiCl–KCl eutectic

Cited by 59 publications

References 24 publications

Method Development for Quantitative Analysis of Actinides in Molten Salts

Method Development for Quantitative Analysis of Actinides in Molten Salts

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

Capillary Imbibition of Gadolinium Halides into WS2 Nanotubes: a Molecular Dynamics View

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

Capillary Imbibition of Gadolinium Halides into WS₂ Nanotubes: a Molecular Dynamics View