Calorimetric measurements were carried out on the electrorefining of copper using different current densities with a Calvet
type microcalorimeter at room temperature. The ratio (R) of the measured heat (Qm orWm) to the input electric energy (Qin orWin) and the excess heat (Qex orWex), i.e. the difference betweenQm (orWm) andQin (orWin) during the electrorefining process were discussed in terms of general thermodynamics. It was found thatR andQex were related to the current density employed in the experiment and varied as a logarithmic function. The results obtained
here indicate that the heat generation under different conditions, such as different currents or voltages, may be caused partially
by the irreversibility of the process or by some unknown processes.
Authors:Z. Zhang, M. Zhong, J. Liu, F. Liu, Z. Wang, F. Zhong, and F. Wu
In this work some calorimetric measurements were also carried out on the electrorefining silver by using different current densities with a Calvet type microcalorimeter at room temperature. The ratio (R) of the measured heat (
ex for silver were related with the current density or cell voltage employed in the experiment. The results obtained here also indicate that the heat generation under different conditions, such as different currents or voltages may be caused partially by the irreversibility of the process or by some unknown processes.
Authors:K. Kim, S. Choi, D. Ahn, S. Paek, B. Park, H. Lee, K. Yi, and I. Hwang
This paper describes ongoing research into the multi-physics model development of an electrorefining process for the treatment
of spent nuclear fuel. A forced convection of molten eutectic (LiCl–KCl) electrolyte in an electrorefining cell is considered
to establish an appropriate electro-fluid model within the 3-dimensional framework of a conventional computational fluid dynamic
model. This computational platform includes the electrochemical reaction rate of charge transfer kinetics which is described
by a Butler–Volmer equation, while mass transport is considered using an ionic transport equation. The coupling of the local
overpotential distribution and uranium concentration gradient makes it possible to predict the local current density distribution
at the electrode surfaces.
Authors:K. Kim, S. Choi, D. Ahn, S. Paek, H. Lee, and I. Hwang
A computational fluid dynamics (CFD)-based multiphysics model of a molten-salt electrorefiner is presented for the computational
electro-fluid analysis. A target model of the electrorefining cell presented here has a structure arranged concentrically
with the cathode annulus surrounding a rotating cruciform anode inside it. This comprehensive approach of a multiphysics model
solves the convective and diffusive transport of ionic uranium and allows for a prediction of the concentration present in
the LiCl–KCl eutectic electrolyte between the electrodes at a current driven condition. The coupling of the local overpotential
distribution and uranium concentration gradient makes it possible to predict the local current density distribution at the
Authors:Sung Park, Dong Cho, Gyu Oh, Jong Lee, Sung Hwang, Young Kang, Hansoo Lee, Eung Kim, and Seong-Won Park
From an electrorefining process, uranium deposits were recovered at the solid cathode of an electrorefining system. The uranium
deposits from the electrorefiner contained about 30–40 wt% salts. In order to recover pure uranium and transform it into metal
ingots, these salts have to be removed. A salt distiller was adapted for a salt evaporation. A batch operation for the salt
removal was carried out by a heating and a vacuum evaporation. The operational conditions were a 700–1,000 °C hold temperature
and less than a 1 Torr under Argon atmosphere, respectively. The behaviors of the salt evaporations were investigated by focusing
on the effects of the pressure and the holding temperature for the salt distillation. The removal efficiencies of the salts
were obtained with regard to the operational conditions. The experimental results of the salt evaporations were evaluated
by using the Hertz-Langmuir relation. The effective evaporation coefficients of this relation were obtained with regards to
the vacuum pressures and the hold temperatures. The higher the vacuum pressure and the higher the holding temperature were,
the higher the removal efficiencies of the salts were.
Authors:Tack-Jin Kim, Yongju Jung, Joon-Bo Shim, Si-Hyung Kim, Seungwoo Paek, Kwang-Rak Kim, Do-Hee Ahn, and Hansoo Lee
In order to enhance the efficiency of pyrochemical technology, especially electrorefining process, physicochemical data of
trivalent uranium in LiCl–KCl eutectic at 773 K were measured, including molar absorptivity, formal potential and diffusion
coefficient of U3+ ions. The molar absorptivities of U3+ were determined to be 765 ± 48 and 686 ± 39 M−1 cm−1 at 465 and 550 nm, respectively. The formal potential of U3+/U4+ redox couple and diffusion coefficient of U3+ ions were measured to be −0.308 V vs. Ag/Ag+ and 8.7 × 10−6 M−1 cm−1, respectively. To elucidate the chemical behavior of U3+ ions under the existence of oxide ions, U3+ ions were reacted with oxides ions in situ produced at the LiCl–KCl media. Surprisingly, it was revealed from XRD patterns
that UO2 was formed from the reaction between U3+ ions and O2− ions with the molar ratio of 1:1.
Energy dispersive X-ray fluorescence spectroscopy (EDXRF) has been used for elemental analysis of Cu−Ni alloy, neodymium aluminide,
and iron and nickel powder. The preparation of Cu−Ni alloy and neodymium aluminide has been carried out by aluminothermic
reduction of mixed oxides of copper and nickel and neodymium oxide respectively. Aqueous electrorefining technique has been
followed for the preparation of iron and nickel powder using Fe−Ni alloy as anode. The determination of major and trace elements
present in the Cu−Ni and, electrolytically refined nickel and iron has been accomplished by EDXRF using Cd109 radioisotope source. In the case of Nd−Al alloy Am241 radioisotope source has been used. The rapid and multielement analysis of the thermit product by EDXRF has aided in the appropriate
variation of the charge constituents during the standardization of the optimum charge composition for Cu−Ni alloy. EDXRF analysis
of electrolytically refined nickel and iron revealed heavy contamination of iron in nickel as compared to that of nickel in
iron. Neodymium content has been found to be 67.68% in Nd−Al alloy.
Authors:Ki-Min Park, Sang-Woon Kwon, Sung-Bin Park, and Jeong-Guk Kim
Recovered salt can be reused in the electrorefining process and the final removed salt from uranium (U) deposits can be fed
into a following U casting process to prepare ingot. Therefore, salt distillation process is very important to increase the
throughput of the salt separation system due to the high U content of spent nuclear fuel and high salt fraction of U dendrites.
Yields on salt recovered by a batch type vacuum distiller transfer device were processed for obtaining pure eutectic salt
and U. In this study, the influence of the various temperature slopes of each zones on salt evaporation and recovery rate
are discussed. From the experimental results, the optimal temperature of each zones appear at the Top Zone and Zone 1 is 850 °C,
Zone 2 is 650 °C and Zone 3 is 600 °C, respectively. In these conditions, the complete evaporation of pure salt in 1.4 h occurred
and the amount of recovered salt was about 99 wt%. The adhered salt in U deposits was separated by a temperature slope zone
of salt distillation equipment. From the experimental results using U deposits, the amount of salt evaporation was achieved
more than 99 wt% and the salt evaporation rate was about 1.16 g/min. Also, the mount of recovered salt was about 99.5 wt%.
Authors:Sung Park, Dong Cho, Moon Woo, Sung Hwang, Young Kang, Jeong Kim, and Hansoo Lee
Uranium dendrites which were deposited at a solid cathode of an electrorefiner contained a certain amount of salts. These
salts should be removed for the recovery of pure metal using a cathode processor. In the uranium deposits from the electrorefining
process, there are actinide chlorides and rare earth chlorides in addition to uranium chloride in the LiCl–KCl eutectic salt.
The evaporation behaviors of the actinides and rare earth chlorides in the salts should be investigated for the removal of
salts in the deposits. Experiments on the salt evaporation of rare earth chlorides in a LiCl–KCl eutectic salt were carried
out. Though the vapor pressures of the rare earth chlorides were lower than those of the LiCl and KCl, the rare earth chlorides
were co-evaporized with the LiCl–KCl eutectic salt. The Hertz–Langmuir relation was applied for this evaporation, and also
the evaporation rates of the salt were obtained. The co-evaporation of the rare earth chlorides and LiCl–KCl eutectic were
Authors:P. Souček, R. Malmbeck, E. Mendes, C. Nourry, and J.-P. Glatz
An electrorefining process in molten chloride salts using solid aluminium cathodes is being developed in Institute for Transuranium
Elements in order to separate actinides (An) from spent nuclear fuel. In this process, the fuel including fission products
(FP) is dissolved into an electrolyte. Without purification of the salt, the process would have to be stopped when the FP
concentration would become too high to allow a selective deposition of An on the cathode. Exhaustive electrolysis is proposed
as the first purification step, consisting of a group-selective recovery of An on solid aluminium cathodes. On the anodic
side, chlorine gas is produced by electrochemical decomposition of the salt. In order to prove the feasibility of the method,
two galvanostatic electrolyses were carried out and the potentials of both electrodes were constantly monitored. Uranium was
recovered from LiCl–KCl melts containing UCl3 and a mixture of UCl3–NdCl3, in which its concentration decreased from 1.7 to 0.1 wt% with no co-deposition of neodymium. Although the maximum applicable
current densities were relatively low, the results are promising, demonstrating high current efficiency and selectivity of
the proposed method. A design and application of a special chlorine gas producing inert anode is also discussed.