Electrochemical transient techniques for determination of uranium and rare-earth metal separation coefficients in molten salts

Kuznetsov, S. A.; Hayashi, Hirokazu; Minato, Kazuo; Gaune‐Escard, M.

doi:10.1016/j.electacta.2005.07.028

Cited by 100 publications

(79 citation statements)

References 21 publications

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“…This vagueness is one of the main disadvantages of this technique, which makes it rather unattractive for quantitative analysis, 12,57,60 though very frequently it is used for both D i and E o evaluation. 4,14,17,19,20,[24][25][26][27][28]30,[32][33][34][35][36][37][38][39][40][42][43][44]49,53,61 Similarly, the semi-integration technique frequently employed to analyze CV data 4,[24][25][26]33,39,50,53 could be a contributing factor to the discrepancy, because the evaluation of the limiting value of the current can be very vague.…”

Section: Resultsmentioning

confidence: 99%

“…It was found, however, that some studies used an incorrect or incomplete theoretical approach for deriving the data; this could have significant impacts on the accuracy of the obtained results. For example, in a few studies 20,34,50 equations describing soluble-soluble couples have been inappropriately used to describe reactions involving the formation of an insoluble product. Kuznetsov and coworkers 19,21 used a relation describing irreversible behavior to calculate the diffusion coefficient of U 3+ from a cyclic voltammogram generated at 1 V/s.…”

Section: Resultsmentioning

confidence: 99%

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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%

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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“…Masset et al 5,6 investigated diffusion coefficients of actinides and lanthanides in LiCl-KCl via cyclic voltammetry (CV) and chronopotentiometry (CP). Kuznetsov et al 7,8 studied the electrochemical behaviors of actinides and rare-earth metals in LiCl-KCl salt. They performed CP and chronoamperometry (CA), and linear sweep voltammetry to determine the diffusion coefficients.…”

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confidence: 99%

Electrochemical Properties and Analyses of CeCl₃in LiCl-KCl Eutectic Salt

Yoon

Phongikaroon

2015

J. Electrochem. Soc.

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Thermodynamic and electrochemical properties of cerium in LiCl-KCl eutectic salt have been measured and studied at different concentrations (0.5 -4 wt%) and temperatures (698 K -798 K) via both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques as a part of developing a fundamental understanding and methodology in materials detection and accountability for pyroprocessing technology. CV experiments were performed to determine the diffusion coefficient and apparent standard potential of CeCl 3 on the tungsten working electrode. The diffusion coefficient was calculated by using Delahay equation, and raging from 0.48 × 10 −5 to 1.01 × 10 −5 cm 2 s −1 . Results reveal that the calculated diffusion coefficient of CeCl 3 in the salt follows the Arrhenius temperature relationship and it is weakly affected by the changes in concentration of CeCl 3 . The apparent standard potentials were calculated from peak potentials showing linear relationship with temperature. Exchange current density values of Ce 3+ /Ce couple in the salt were obtained from EIS experiments, ranging from 0. Pyroprocessing technology has been proposed as another promising method for the recovery and recycle of uranium and actinide elements from the used nuclear fuel. An essential step in this technology is the electrorefining process in which uranium is selectively recovered by using solid cathodes in chloride-based molten salt at high temperature.1 Then, co-recovery of uranium and transuranic elements can be accomplished by replacing the solid cathodes with a liquid cadmium cathode because the reduction potentials of the elements become close when the liquid cadmium is used as a cathode electrode.2,3 Since uranium is the major element in most nuclear fuel cycle paths as well as pyroprocessing technology, the assessment of accurate thermochemical data for the element in the molten salt is extremely important. 4Many studies on the thermochemical properties of uranium have been done in LiCl-KCl molten eutectic salt in different temperature ranges. Masset et al. 5,6 investigated diffusion coefficients of actinides and lanthanides in LiCl-KCl via cyclic voltammetry (CV) and chronopotentiometry (CP). Kuznetsov et al. 7,8 studied the electrochemical behaviors of actinides and rare-earth metals in LiCl-KCl salt. They performed CP and chronoamperometry (CA), and linear sweep voltammetry to determine the diffusion coefficients. Hoover et al. in 2014 9 extended the uranium concentration in LiCl-KCl molten salt up to 10 wt% and observed the electrochemical and thermodynamic behaviors of uranium using CV, CP, and anodic stripping voltammetry. These data are valuable to a development of kinetic models, which can be useful for understanding the main features of actinide deposition at the electrode surface, and also for prediction of material distribution in an electrorefiner of a safeguarding aspect. Zhang 10 developed a kinetic model for electrorefining system showing that the model is capable of predicting the kinetic features and...

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“…[22][23][24] Because they are in agreement at approximately 1:0 Â 10 À5 cm 2 /s, this value was used in the following calculations. The diffusion coefficient of Zr(IV) in LiCl-KCl at 773 K has been determined to be 1:13 Â 10 À5 cm 2 /s by a capillary method.…”

Section: Parameters In Layer Formation Modelmentioning

confidence: 99%

Analyses of Anodic Behavior of Metallic Fast Reactor Fuel Using a Multidiffusion Layer Model

Iizuka¹,

Moriyama²

2010

J. Nucl. Sci. Technol.

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Anodic behavior of U-Zr or U-Pu-Zr alloys during electrorefining in molten chloride electrolyte was modeled on the basis of recent findings from the observation of anode residues after a number of electrorefining tests, such as the formation of an intermediate region that has a composition corresponding to the phase. Simulation of anodic dissolution of the U-Zr alloy during the engineering-scale electrorefining tests using the model showed that the calculated dissolution ratios of uranium and zirconium were in agreement with the experimental results when the alloy pin was chopped to as short as 5 mm. Three runs of laboratory-scale electrorefining tests with uncladded U-Pu-Zr ternary alloy were also simulated. The characteristic change of the anode potential during these tests was well reproduced in the calculation using the fitting parameters for uranium activity in the porous zirconium layer. The results of some predictive calculations showed that the required period to attain a certain uranium dissolution ratio is drastically increased with the increase in pin length, and that the zirconium dissolution ratio is largely increased when a higher anodic current density is applied to improve the electrorefining processing rate.

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Electrochemical transient techniques for determination of uranium and rare-earth metal separation coefficients in molten salts

Cited by 100 publications

References 21 publications

Method Development for Quantitative Analysis of Actinides in Molten Salts

Method Development for Quantitative Analysis of Actinides in Molten Salts

Electrochemical Properties and Analyses of CeCl₃in LiCl-KCl Eutectic Salt

Analyses of Anodic Behavior of Metallic Fast Reactor Fuel Using a Multidiffusion Layer Model

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Electrochemical transient techniques for determination of uranium and rare-earth metal separation coefficients in molten salts

Cited by 100 publications

References 21 publications

Method Development for Quantitative Analysis of Actinides in Molten Salts

Method Development for Quantitative Analysis of Actinides in Molten Salts

Electrochemical Properties and Analyses of CeCl3in LiCl-KCl Eutectic Salt

Analyses of Anodic Behavior of Metallic Fast Reactor Fuel Using a Multidiffusion Layer Model

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Electrochemical Properties and Analyses of CeCl₃in LiCl-KCl Eutectic Salt