Liquid Cd Research Articles

Application of Electrochemical Method to Measure Diffusion Coefficient in Liquid Metal

An electrochemical method was proposed as one of the techniques to measure a diffusion coefficient of a solute in liquid metal; the diffusion coefficient was evaluated from the results of chronopotentiometry using a liquid metal electrode containing the solute. Diffusion coefficients of rare–earths (La, Pr, Nd, Gd, Y and Sc) in liquid Cd metal, which were inevitable physical constants to analyze pyrometallurgical reprocessing for spent nuclear fuels kinetically, were measured in LiCl–KCl melts.

Thermodynamic properties and microscopic structure of liquid Cd–Na alloys by estimating complex concentration in a regular associated solution

The thermodynamic and microscopic structure of Cd – Na liquid alloy at 673 K has been studied by using regular associated solution model. This model has been utilized to determine the concentration of the complexes Cd 2 Na in Cd – Na alloys in molten state at 673 K. The concentration of the complexes is then used to find free energy of mixing, heat of mixing, entropy of mixing, activity, concentration fluctuations in long wavelength limit S cc (0) and the Warren Cowley short-range parameter α 1. The analysis suggests that this alloy is of a weakly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloy is more ordered in Cd-rich region. The alloy behaves like a segregating system in Na-rich region. The observed asymmetry in the properties of mixing of Cd – Na alloy in molten state is successfully explained by assuming Cd 2 Na complex on the basis of regular associated solution model.

STATUS OF PYROPROCESSING TECHNOLOGY DEVELOPMENT IN KOREA

The Korea Atomic Energy Research Institute (KAERI) has been developing pyroprocessing technology for recycling useful resources from spent fuel since 1997. The process includes pretreatment, electroreduction, electrorefining, electrowinning, and a waste salt treatment system. This paper briefly addresses unit processes and related innovative technologies. As for the electroreduction step, a stainless steel mesh basket was applied for adaption of granules of uranium oxide. This basket was designed for ready handling and transfer of feed material. A graphite cathode was used for the continuous collection of uranium dendrite in the electrorefining system. This enhances the throughput of the electrorefiner. A particular mesh type stirrer was designed to inhibit uranium spill-over at the liquid Cd crucible. A residual actinide recovery system was also tested to recover TRU tracer. In order to reduce the waste volume, a crystallization method is employed for Cs and Sr removal. Experiments on the unit processes were tested successfully, and based on the results, engineering-scale equipment has been designed for the PRIDE (PyRoprocess Integrated inactive DEmonstration facility).

Countercurrent Extraction Test with Continuous Flow of Molten LiCl-KCl Salt and Liquid Cd for Pyro-Reprocessing of Metal FBR Fuel

The three-stage countercurrent extraction test with molten LiCl-KCl and liquid Cd was carried out for the development of spent salt treatment process in pyrometallurgical reprocessing of metal FBR fuel. Both salt and Cd solvent were supplied successively from each feed tank into the extractor at a constant flow rate and recovered separately into individual recovery tanks. Uranium, transuranic elements, and rareearth elements were substituted by Ce, Gd, and Y, respectively. More than 98% of Ce and 93% of Gd were recovered, and 27% of Y was corecovered in the Cd solvent. The separation factors of Gd and Y against Ce were evaluated to be 0.28–0.29 and 0.0057–0.0073, respectively. The former is almost equal to and the latter is better than that in the equilibrium. As the connecting part between each stage had a simple structure, a small amount of Cd in each stage mixed with that in the neighboring stage, which made the separation efficiency lower than expected. A calculation study showed the relationship between the Cd mixing rate and recovery yield or separation factor, and it showed that the recovery yield and separation efficiency were expected to be much improved by the modification of the connecting part to prevent Cd from mixing.

Countercurrent Extraction Test with Continuous Flow of Molten LiCl-KCl Salt and Liquid Cd for Pyro-Reprocessing of Metal FBR Fuel

Countercurrent Extraction Test with Continuous Flow of Molten LiCl-KCl Salt and Liquid Cd for Pyro-Reprocessing of Metal FBR Fuel

Thermodynamic Evaluation of Liquid Cd Cathode Containing U and Pu

In our previous study, a mixture of U and Pu was recovered in liquid Cd cathode from molten salt under various conditions of the U:Pu ratio. Two important things were observed. The first was that three kinds of precipitated phase had been detected in the saturated liquid Cd cathode, such as a U metal and two kinds of U-Pu-Cd compound. The compositions of the compounds were roughly (U+Pu):Cd = 1:11 and (U+Pu):Cd = 1:6. The second was that the U metal had selectively precipitated in the saturated liquid Cd cathode under the condition that the U:Pu ratio is higher than about 0.8 in the liquid Cd phase. In the present study, phase diagrams were evaluated by the CALPHAD method on the liquid Cd cathode containing U and Pu. The U-Pu-Cd compounds were modeled as MCd11-type and MCd6-type, respectively, based on the reported binary phase diagrams of U-Cd and Pu-Cd. The calculated result reasonably agreed with the experimental observations. The variations in the U and Pu activities were estimated along with the U:Pu ratio, which is related to the precipitation of various phases in the liquid Cd cathode.

Electrolysis of Burnup-Simulated Uranium Nitride Fuels in LiCl-KCl Eutectic Melts

The electrochemical behavior of burnup-simulated uranium nitride fuels containing representative solid fission product elements, UN+Mo (Mo = 2.84 wt%), UN+Pd (Pd = 4.6 wt%) and (U, Nd)N (NdN = 8.0 wt%), was investigated in the molten LiCl-KCl eutectic salt with 0.54 wt% UCl3 in order to clarify the effects of fission products on the dissolution of actinide nitrides and the behavior of FPs in the electrorefining of spent nitride fuel. The rest potentials of burnup-simulated UN pellets were similar to that of pure UN. The electrochemical dissolution of UN began at about _0:75V vs Ag/AgCl reference electrode in all samples as well as that of pure UN. After the electrolyses at the constant anodic potential of −0:65––0:60V vs Ag/AgCl, most of UN was dissolved into LiCl-KCl as UCl3 at the anode, and U was recovered in the liquid Cd cathode in all samples. Furthermore, Nd was dissolved at the anode and accumulated into LiCl-KCl as NdCl3, while Mo and Pd were not dissolved but remained at the anode.

Development of High-Temperature Transport Technologies for Liquid Cadmium in Pyrometallurgical Reprocessing

Pyrometallurgical reprocessing is one of the most promising technologies for the advanced fuel cycle with favorable economic potential and intrinsic proliferation-resistance. The feasibility of pyrometallurgical reprocessing has been studied through many laboratory-scale experiments. Hence the development of the engineering technology necessary for pyrometallurgical reprocessing is a key issue for its industrialization. The development of high-temperature transport technologies for molten salt and liquid cadmium is crucial for pyrometallurgical processing; however, there have been a few transport studies on high-temperature fluids. In this study, a metal transport test rig was installed in an argon glove box with the aim of developing technologies for transporting liquid cadmium at approximately 773 K. The transport of liquid Cd using gravity was controlled by adjusting the valve. The liquid Cd was transported by a suction pump against a 0.93 m head and the transport amount of Cd was well controlled with the Cd amount and the position of the suction tube. The transportation of liquid cadmium at approximately 700 K could be controlled at a rate of 0.5–2.5 dm3/min against a 1.6 m head using a centrifugal pump.

Electrolysis of AmN in LiCl-KCl Eutectic Melts and Renitridation of Am Recovered in Liquid Cd Cathode

R&D of the nitride fuel cycle technology is underway at Japan Atomic Energy Agency (JAEA). Behavior of americium (Am) in the pyrochemical process, which includes anodic dissolution of AmN and recovery of Am into a liquid cadmium (Cd) cathode by electrolysis in LiCl-KCl eutectic melts, and nitride formation of Am recovered in liquid Cd, is presented.

Thermodynamic Evaluation of Liquid Cd Cathode Containing U and Pu

In our previous study, a mixture of U and Pu was recovered in liquid Cd cathode from molten salt under various conditions of the U:Pu ratio. Two important things were observed. The first was that three kinds of precipitated phase had been detected in the saturated liquid Cd cathode, such as a U metal and two kinds of U-Pu-Cd compound. The compositions of the compounds were roughly (U+Pu):Cd = 1:11 and (U+Pu):Cd = 1:6. The second was that the U metal had selectively precipitated in the saturated liquid Cd cathode under the condition that the U:Pu ratio is higher than about 0.8 in the liquid Cd phase. In the present study, phase diagrams were evaluated by the CALPHAD method on the liquid Cd cathode containing U and Pu. The U-Pu-Cd compounds were modeled as MCd11-type and MCd6-type, respectively, based on the reported binary phase diagrams of U-Cd and Pu-Cd. The calculated result reasonably agreed with the experimental observations. The variations in the U and Pu activities were estimated along with the U:Pu ratio, which is related to the precipitation of various phases in the liquid Cd cathode.

Electrolysis of Burnup-Simulated Uranium Nitride Fuels in LiCl-KCl Eutectic Melts

The electrochemical behavior of burnup-simulated uranium nitride fuels containing representative solid fission product elements, UN+Mo (Mo = 2.84 wt%), UN+Pd (Pd = 4.6 wt%) and (U, Nd)N (NdN = 8.0 wt%), was investigated in the molten LiCl-KCl eutectic salt with 0.54 wt% UCl3 in order to clarify the effects of fission products on the dissolution of actinide nitrides and the behavior of FPs in the electrorefining of spent nitride fuel. The rest potentials of burnup-simulated UN pellets were similar to that of pure UN. The electrochemical dissolution of UN began at about _0:75V vs Ag/AgCl reference electrode in all samples as well as that of pure UN. After the electrolyses at the constant anodic potential of −0:65––0:60V vs Ag/AgCl, most of UN was dissolved into LiCl-KCl as UCl3 at the anode, and U was recovered in the liquid Cd cathode in all samples. Furthermore, Nd was dissolved at the anode and accumulated into LiCl-KCl as NdCl3, while Mo and Pd were not dissolved but remained at the anode.

Electrochemical Behavior of Zr on a Liquid Cd Electrode in LiCl–KCl Eutectic Melts

The electrochemical behavior of zirconium on a liquid cadmium electrode was studied in LiCl–KCl melts containing at 773 K. In a cyclic voltammogram of the liquid cadmium electrode, a cathodic peak was observed at around (vs ) as well as at attributed to zirconium metal deposition. Because the deposit obtained by potentiostatic electrolysis at was confirmed to be from X-ray diffraction analysis, the cathodic peak at corresponded to formation. The open-circut-potential of the liquid cadmium electrode with was measured to calculate thermodynamic properties such as relative partial molar Gibbs energies of zirconium in . The quantity of zirconium recovered in the liquid cadmium electrode by the potentiostatic electrolysis at was measured by inductively coupled plasma-atomic emission spectroscopy. The result indicated of the zirconium recovery efficiency, which was defined as the quantity of electricity corresponding to the recovered zirconium divided by the total quantity of passed electricity.

Cyclic Voltammetry Behavior of Americium at a Liquid Cadmium Electrode in LiCl-KCl Eutectic Melts

The electrode reactions of americium at a liquid cadmium electrode were investigated by cyclic voltammetry of AmCl3-(LiCl-KCl)eut. at both 723 and 773 K in comparison with those at a molybdenum electrode. The redox peaks assigned to Am(III)/Am(0) (in Cd) were observed with the liquid Cd electrode, while the redox reactions of Am(III)/Am(II) and Am(II)/Am(0) were observed with the Mo electrode. The formal standard potential of Am(III)/Am(0) obtained with the liquid Cd electrode is more positive than those calculated for the Mo electrode at both 723 and 773 K. The potential shifts were attributed to the lowering of the activity of Am by the formation of the intermetallic compound at the interface between Cd and the molten salt. The Gibbs free energies of formation of the Am-Cd intermetallic compound, which could be AmCd6, are estimated to be -119 and -113 kJ/mol at 723 and 773 K, respectively.

Neutron and X-ray scattering experiments on fully deuterated liquid N-methylacetamide CD 3CONDCD 3 at various temperatures and under pressure

A structural investigation of liquid N-methylacetamide (NMA) was performed in the 308–383 K temperature range by both neutron and X-ray diffraction and using only neutron diffraction at 308 K and pressures of up to 4 kbar. The analysis of experimental data yields the total structure factor, the molecular form factor, and the distinct pair correlation function. The spectra obtained are consistent with the presence of hydrogen-bonded open chain in the liquid state. Surprisingly, our measurements clearly show, in contrast to similar liquids, that the N⋯O and D⋯O lengths increase in liquid NMA with increasing temperature, while no significant variation is observed with increasing pressure.

Single-Stage Extraction Test with Continuous Flow of Molten LiCl-KCl Salt and Liquid Cd for Pyro-Reprocessing of Metal FBR Fuel

A single-stage extraction test with the continuous flow of both molten salt and liquid Cd was carried out as a preliminary step of the development of a multistage countercurrent extraction process for the pyrometallurgical reprocessing of metal FBR fuel. Ce, Gd, and Y were selected as the substitutes for U, other actinides, and rare-earth elements, respectively. More than 97% of Ce could be recovered in one of the experiments, in which 97% of Gd and 63% of Y were also recovered. This meant that high recovery yield could be obtained in the system, but mutual separation was not sufficient when the high recovery yield was required in a single-stage extraction. In another experiment in which the recovery yields of Ce, Gd, and Y were about 87, 70, and 8%, respectively, the separation factors of Gd and Y against Ce were 0.27 and 0.0092, respectively, which were about the same as their equilibrium values. The result showed that higher separation efficiency was achieved under the condition of relatively lower recovery yield. The mass transfer coefficient of rare-earth elements in the salt was estimated to be 0.14 cm/s, which was much larger than that in the previous experiments without a baffle plate in the extractor.

The interfacial free energy of solid Sn on the boundary interface with liquid Cd–Sn eutecticsolution

Equilibrated grain boundary groove shapes for solid Sn in equilibrium withCd–Sn liquid were directly observed after annealing a sample at the eutectictemperature for about 8 days. The thermal conductivities of the solid phase,KS, and theliquid phase, KL, for the groove shapes were measured. From the observed groove shapes, theGibbs–Thomson coefficients were obtained with a numerical method, using the measuredG,KS and KL values. The solid–liquid interfacial energy of solid Sn in equilibrium with Cd–Sn liquid wasdetermined from the Gibbs–Thomson equation. The grain boundary energy for solid Snwas also calculated from the observed groove shapes.

Improvement in Sachdeva's Multiphase Choke Flow Model Using Field Data

Abstract Sachdeva's choke flow model has been found capable of predicting critical-subcritical boundary and liquid and gas flow rates for multiphase crude systems. Although this model was shown to be accurate by Sachdeva et al.(15) in their original paper using laboratory and field data, inaccuracy of the model has been found in other field applications. In this study, the accuracy of the choke model was evaluated using data from 239 oil wells and 273 gas condensate wells in Southwest Louisiana. Comparisons of results from measurements and model calculations indicate that the model is more accurate for oil wells than for gas condensate wells. It was found that the error of the model could be minimized using different values of choke discharge coefficient (CD). For oil wells, CD = 1.08 should be used for liquid rate prediction and CD = 0.78 should be used for gas rate predictions. For gas condensate wells, CD = 1.07 should be used for gas rate predictions and CD = 1.53 should be used for liquid rate predictions. Introduction Wellhead chokes are equipment used in the oil and gas industry to control fluid production rates from wells, to maintain stable pressure downstream from the choke and to provide the necessary backpressure to a reservoir to avoid formation damage from excessive drawdown. Because oil and gas production rates are extremely sensitive to choke size, accurate modeling of choke performance is vitally important for petroleum engineers in oil production simulation. Tangren et al.(1) performed the first investigation on gas-liquid two-phase flow through restrictions. They presented an analysis of the behaviour of an expanding gas-liquid system. They showed that when gas bubbles are added to an incompressible fluid above a critical flow velocity, the medium becomes incapable of transmitting a pressure change upstream against the flow. Several empirical choke flow models have been developed in the past half century. They generally take the following form for sonic flow: Equation (1) (Available in full paper) where: Pwh = upstream (wellhead) pressure, kPa Q = gross liquid rate, m3/day R = gas-liquid ratio, scm/m3 S = choke size, cm and C, m and n are empirical constants related to fluid properties. On the basis of the production data from Ten Section Field in Cal-ifornia, Gilbert(2) found the values for C, m and n to be 2.4644, 0.546 and 1.89, respectively. Other values for the constants were proposed by different researchers including Baxendell(3), Ros(4) and Achong(5). Poettmann and Beck(6) extended the work of Ros to develop charts for different API crude oils. Omana et al.(7) derived dimensionless choke correlations for water-gas systems. Fortunati(8) was the first investigator who presented a model that can be used to calculate critical and subcritical two-phase flow through chokes. Ashford(9) also developed a relation for two-phase critical flow based on the work of Ros. Gould(10) plotted the critical-subcritical boundary defined by Ashford, showing that different values of the polytropic exponents yield different boundaries. Ashford and Pierce(11) derived an equation to predict the critical pressure ratio.

Electrode Reaction of the U3+/U Couple at Liquid Cd and Bi Electrodes in LiCl-KCl Eutectic Melts

The electrode reactions of the Np3+/Np couple at liquid Cd and Bi electrodes were investigated by cyclic voltammetry at 723, 773 and 823 K in the LiCl–KCl eutectic melt. It was found that the diffusion of Np3+ in the salt phase was the rate-determining step in the cathodic reaction when the concentration of NpCl3 was less than about 1 wt % and the liquid Cd or Bi phase was not saturated with Np. The redox potentials of the Np3+/Np couple at the liquid Cd electrode at 723, 773 and 823 K were observed to be more positive than those at the Mo electrode by 0.158, 0.140 and 0.126 V, respectively. The potential shift results from a lowering of the activity of Np in the Cd phase according to the formation of the NpCd11 alloy at 723 K and NpCd6 at 773 and 823 K. The redox potentials of the Np3+/Np couple at the liquid Bi electrode at 723, 773 and 823 K were more positive than those at the Mo electrode by 0.427, 0.419 and 0.410 V, respectively, which is attributable to a lowering of the activity of Np in the Bi phase due to the formation of NpBi2.

Single-Stage Extraction Test with Continuous Flow of Molten LiCl-KCl Salt and Liquid Cd for Pyro-Reprocessing of Metal FBR Fuel

Single-Stage Extraction Test with Continuous Flow of Molten LiCl-KCl Salt and Liquid Cd for Pyro-Reprocessing of Metal FBR Fuel

Separation behaviors of actinides from rare-earths in molten salt electrorefining using saturated liquid cadmium cathode

Electrorefining in the molten LiCl–KCl eutectic salt containing actinide (An) and rare-earth (RE) elements was conducted to recover An elements up to 10 wt% into liquid cadmium (Cd) cathode, which is much higher than the solubility of the An elements in liquid Cd at the experimental temperature of 773 K. In the saturated Cd cathode, the An and RE elements were recovered forming a PuCd 11 type compound, MCd 11 (M = An and RE elements). The separation factors of element M against Pu defined as [M/Pu in Cd alloy (cathode)]/[M/Pu in molten salt] were calculated for the saturated Cd cathode including MCd 11. The separation factors were 0.011, 0.044, 0.064, and 0.064 for La, Ce, Pr, and Nd, respectively. These values were a little differed from 0.014, 0.038, 0.044, and 0.043 for the equilibrium unsaturated liquid Cd, respectively. The above slight differences were considered to be caused by the solid phase formation in the saturated Cd cathode and the electrochemical transfer of the An and RE elements in the molten salt.