Thermodynamic properties of trivalent lanthanide and actinide ions in molten mixtures of LiCl and KCl

Fukasawa, Kazuhito; Uehara, Akihiro; Nagai, Takayuki; Sato, Nobuaki; Fujii, Toshiyuki; Yamana, Hideaki

doi:10.1016/j.jnucmat.2012.01.009

Cited by 41 publications

(26 citation statements)

References 37 publications

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“…They receive much attention due to their diverse but promising applications that range from metal production [1][2][3] , the pyrochemical treatment of nuclear waste [4][5][6][7] , primary or secondary coolants in several concepts of generation IV fission 8 and fusion 9 nuclear reactors, and electricity storage devices 10 . In the context of nuclear applications, the nuclear reactions produce rare earth elements in the core.…”

Section: Introductionmentioning

confidence: 99%

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Levesque¹,

Sarou‐Kanian²,

Salanne³

et al. 2013

The Journal of Chemical Physics

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The transport properties of molten LiF-YF 3 mixtures have been studied by pulsed field gradient nuclear magnetic resonance spectroscopy, potentiometric experiments, and molecular dynamics simulations. The calculated diffusion coefficients and electric conductivities compare very well with the measurements across a wide composition range. We then extract static (radial distribution functions, coordination numbers distributions) and dynamic (cage correlation functions) quantities from the simulations. Then, we discuss the interplay between the microscopic structure of the molten salts and their dynamic properties. It is often considered that variations in the diffusion coefficient of the anions are mainly driven by the evolution of its coordination with the metallic ion (Y 3+ here). We compare this system with fluorozirconate melts and demonstrate that the coordination number is a poor indicator of the evolution of the diffusion coefficient. Instead, we propose to use the ionic bonds lifetime. We show that the weak Y-F ionic bonds in LiF-YF 3 do not induce the expected tendency of the fluoride diffusion coefficient to converge toward the one of yttrium cation when the content in YF 3 increases. Implications on the validity of the Nernst-Einstein relation for estimating the electrical conductivity are discussed.

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Section: Introductionmentioning

confidence: 99%

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Levesque¹,

Sarou‐Kanian²,

Salanne³

et al. 2013

The Journal of Chemical Physics

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“…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.…”

mentioning

confidence: 99%

“…They calculated the potential difference between the cathodic and anodic peaks, which was in the range of 0.010-0.015 V. This shift was explained as an indication of nucleation and crystallization processes that influence the electrodeposition process, but no further analysis was reported. Fukasawa et al 1 studied uranium and several lanthanide (La, Ce, Pr, Tb, and Er) elements in LiCl-KCl eutectic. The difference between cathodic and anodic peaks in the voltammograms was found to be 0.020 V more negative than the theoretical value.…”

mentioning

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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“…Так, эти вопросы, а также определение кинетических параметров электродных процессов в низкотем-пературном хлоридном расплаве LiCl-KCl и рас-плаве LiCl-CaCl 2 являются предметом изучения японских, испанских и российских ученых [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Электрохимическому получению сплавов интер-металлических соединений на основе празеоди-ма и неодима в галогенидных расплавах методом диффузионного насыщения посвящены работы [16][17][18].…”

Section: № 1 2014unclassified

“…2). Аналогично получается и гекса борид празеодима при потенциостатическом электролизе расплава KCl-NaCl-PrCl 3 Найдены оптимальные соотношения концен-траций, интервалы плотностей тока и напряжения на ванне для получения наноразмерного порошка гексаборида неодима. Значения среднего размера частиц продукта гальваностатического электро-лиза расплава KCl-NaCl-NdCl 3 -KBF 4 в зависимо-сти от состава и плотности тока представлены в табл.…”

Section: № 1 2014unclassified