SEPARATION OF CsCl FROM LiCl-CsCl MOLTEN SALT BY COLD FINGER MELT CRYSTALLIZATION

Versey, Joshua R.,Phongikaroon, Supathorn,Simpson, Michael F. Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.3

This study provides a fundamental understanding of a cold finger melt crystallization technique by exploring the heat and mass transfer processes of cold finger separation. A series of experiments were performed using a simplified LiCl-CsCl system by varying initial CsCl concentrations (1, 3, 5, and 7.5 wt%), cold finger cooling rates (7.4, 9.8, 12.3, and 14.9 L/min), and separation times (5, 10, 15, and 30 min). Results showed a potential recycling rate of 0.36 g/min with a purity of 0.33 wt% CsCl in LiCl. A CsCl concentrated drip formation was found to decrease crystal purity especially for smaller crystal formations. Dimensionless heat and mass transfer correlations showed that separation production is primarily influenced by convective transfer controlled by cooling gas flow rate, where correlations are more accurate for slower cooling gas flow rates.

Investigation on Dissolution and Removal of Adhered LiCl-KCl-UCl₃ Salt From Electrodeposited Uranium Dendrites using Deionized Water, Methanol, and Ethanol

Killinger, Dimitris Payton,Phongikaroon, Supathorn Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.4

Deionized water, methanol, and ethanol were investigated for their effectiveness at dissolving LiCl-KCl-UCl3 at 25, 35, and 50℃ using inductively coupled plasma mass spectrometry (ICP-MS) to study the concentration evolution of uranium and mass ratio evolutions of lithium and potassium in these solvents. A visualization experiment of the dissolution of the ternary salt in solvents was performed at 25℃ for 2 min to gain further understanding of the reactions. Aforementioned solvents were evaluated for their performance on removing the adhered ternary salt from uranium dendrites that were electrochemically separated in a molten LiCl-KCl-UCl3 electrolyte (500℃) using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Findings indicate that deionized water is best suited for dissolving the ternary salt and removing adhered salt from electrodeposits. The maximum uranium concentrations detected in deionized water, methanol, and ethanol for the different temperature conditions were 8.33, 5.67, 2.79 μg·L-1 for 25℃, 10.62, 5.73, 2.50 μg·L-1 for 35℃, and 11.55, 6.75, and 4.73 μg·L-1 for 50℃. ICP-MS analysis indicates that ethanol did not take up any KCl during dissolutions investigated. SEM-EDS analysis of ethanol washed uranium dendrites confirmed that KCl was still adhered to the surface. Saturation criteria is also proposed and utilized to approximate the state of saturation of the solvents used in the dissolution trials.

Assessment on Recovery of Cesium, Strontium, and Barium From Eutectic LiCl-KCl Salt With Liquid Bismuth System

Woods, Michael E.,Phongikaroon, Supathorn Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.4

This study provides an assessment on a proposed method for separation of cesium, strontium, and barium using electrochemical reduction at a liquid bismuth cathode in LiCl-KCl eutectic salt, investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS). CV studies were performed at temperatures of 723-823 K and concentrations of the target species up to 4.0wt%. Redox reactions occurring during potential sweeps were observed. Concentration of BaCl2 in the salt did not seem to influence the diffusivity in the studied concentration range up to 4.0wt%. The presence of strontium in the system affected the redox reaction of lithium; however, there were no distinguishable redox peaks that could be measured. Impedance spectra obtained from EIS methods were used to calculate the exchange current densities of the electroactive active redox couple at the bismuth cathode. Results show the rate-controlling step in deposition to be the mass transport of Cs+ ions from the bulk salt to the cathode surface layer. Results from SEM-EDS suggest that Cs-Bi and Sr-Bi intermetallics from LiCl-KCl salt are not thermodynamically favorable.

Review, Assessment, and Learning Lesson on How to Design a Spectroelectrochemical Experiment for the Molten Salt System

Dimitris Killinger,Supathorn Phongikaroon 한국방사성폐기물학회 2022 방사성폐기물학회지 Vol.20 No.2

This work provided a review of three techniques—(1) spectrochemical, (2) electrochemical, and (3) spectroelectrochemical– for molten salt medias. A spectroelectrochemical system was designed by utilizing this information. Here, we designed a spectroelectrochemical cell (SEC) and calibrated temperature controllers, and performed initial tests to explore the system’s capability limit. There were several issues and a redesign of the cell was accomplished. The modification of the design allowed us to assemble, align the system with the light sources, and successfully transferred the setup inside a controlled environment. A preliminary run was executed to obtain transmission and absorption background of NaCl-CaCl2 salt at 600°C. It shows that the quartz cuvette has high transmittance effects across all wavelengths and there were lower transmittance effects at the lower wavelength in the molten salt media. Despite a successful initial run, the quartz vessel was mated to the inner cavity of the SEC body. Moreover, there was shearing in the patch cord which resulted in damage to the fiber optic cable, deterioration of the SEC, corrosion in the connection of the cell body, and fiber optic damage. The next generation of the SEC should attach a high temperature fiber optic patch cords without introducing internal mechanical stress to the patch cord body. In addition, MACOR should be used as the cell body materials to prevent corrosion of the surface and avoid the mating issue and a use of an adapter from a manufacturer that combines the free beam to a fiber optic cable should be incorporated in the future design.

Feasibility Study on Aluminum Under Laser Ablation for Corrosion Resistance in Molten Salt

Peggy T. Milota,Supathorn Phongikaroon 한국방사성폐기물학회 2024 방사성폐기물학회지 Vol.22 No.1

Fundamental aspects of creating passivation layers for corrosion resistance in nuclear engineering applications, specifically the ability to form complete layers versus porous ones, are being explored in this study. Utilizing a laser ablation technique, 1,064 nm fire at 10 Hz with 60 pulses per shot and 0.5 mm between impact points, aluminum samples are treated in an attempt to create a fully formed passivation layer that will be tested in a LiCl-KCl eutectic salt. By placing these samples into an electrochemical environment mimicking a pyroprocessing system, corrosion rates, resistances and material characteristics are tested for one week and then compared between treated and untreated samples. In initial testing, linear sweep voltammetry indicates corrosion current density for the untreated sample at −0.038 mA·cm−2 and treated samples at −0.024 mA·cm−2 and −0.016 mA·cm−2, respectively. This correlates to a control sample corrosion rate of −0.205 mm·yr−1 and treated rates of −0.130 mm·yr−1 and −0.086 mm·yr−1 for samples 1 and 2. In addition, electrochemical impedance spectroscopy circuits show application of a longer-lasting porous passivation layer on the treated metal, compared to the naturally forming layer. However, the current technique fails to create a uniform protection layer across the sample.

ANALYSIS OF EQUILIBRIUM METHODS FOR THE COMPUTATIONAL MODEL OF THE MARK-IV ELECTR OREFINER

Cumberland, Riley,Hoover, Robert,Phongikaroon, Supathorn,Yim, Man-Sung Korean Nuclear Society 2011 Nuclear Engineering and Technology Vol.43 No.6

Two computational methods for determining equilibrium states for the Mark-IV electrorefiner (ER) have been assessed to improve the current computational electrorefiner model developed at University of Idaho. Both methods were validated against measured data to better understand their effects on the calculation of the equilibrium compositions in the ER. In addition, a sensitivity study was performed on the effect of specific unknown activity coefficients-including sodium in molten cadmium, zirconium in molten cadmium, and sodium chloride in molten LiCl-KCl. Both computational methods produced identical results, which stayed within the 95% confidence interval of the experimental data. Furthermore, sensitivity to unavailable activity coefficients was found to be low (a change in concentration of less than 3 ppm).

Separation of CsCl from LiCl-CsCl Molten Salt by Cold Finger Melt Crystallization

JOSHUA R. VERSEY,SUPATHORN PHONGIKAROON,Michael F. Simpson 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.3

This study provides a fundamental understanding of a cold finger melt crystallization technique by exploring the heat andmass transfer processes of cold finger separation. A series of experiments were performed using a simplified LiCl-CsClsystem by varying initial CsCl concentrations (1, 3, 5, and 7.5 wt%), cold finger cooling rates (7.4, 9.8, 12.3, and 14.9 L/min),and separation times (5, 10, 15, and 30 min). Results showed a potential recycling rate of 0.36 g/min with a purity of 0.33wt% CsCl in LiCl. A CsCl concentrated drip formation was found to decrease crystal purity especially for smaller crystalformations. Dimensionless heat and mass transfer correlations showed that separation production is primarily influenced byconvective transfer controlled by cooling gas flow rate, where correlations are more accurate for slower cooling gas flow rates

SEPARATION OF STRONTIUM AND CESIUM FROM TERNARY AND QUATERNARY LITHIUM CHLORIDE-POTASSIUM CHLORIDE SALTS VIA MELT CRYSTALLIZATION

AMMON N. WILLIAMS,MICHAEL PACK,SUPATHORN PHONGIKAROON 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.7

Separation of cesium chloride (CsCl) and strontium chloride (SrCl2) from the lithiumchloride-potassium chloride (LiCl-KCl) salt was studied using a melt crystallization processsimilar to the reverse vertical Bridgeman growth technique. A ternary SrCl2-LiCl-KCl saltwas explored at similar growth rates (1.8e5 mm/h) and compared with CsCl ternary resultsto identify similarities. Quaternary experiments were also conducted and compared withthe ternary cases to identify trends and possible limitations to the separations process. Inthe ternary case, as much as 68% of the total salt could be recycled per batch process. In thequaternary experiments, separation of Cs and Sr was nearly identical at the slower rates;however, as the growth rate increased, SrCl2 separated more easily than CsCl. The quaternaryresults show less separation and rate dependence than in both ternary cases. As anestimated result, only 51% of the total salt could be recycled per batch. Furthermore, twomodels have been explored to further understand the growth process and separation. Acomparison of the experimental and modeling results reveals that the nonmixed model fitsreasonably well with the ternary and quaternary data sets. A dimensional analysis wasperformed and a correlation was identified to semipredict the segregation coefficient.

ANALYSIS OF EQUILIBRIUM METHODS FOR THE COMPUTATIONAL MODEL OF THE MARK-IV ELECTR OREFINER

RILEY CUMBERLAND,ROBERT HOOVER,SUPATHORN PHONGIKAROON,임만성 한국원자력학회 2011 Nuclear Engineering and Technology Vol.43 No.6

Two computational methods for determining equilibrium states for the Mark-IV electrorefiner (ER) have been assessed to improve the current computational electrorefiner model developed at University of Idaho. Both methods were validated against measured data to better understand their effects on the calculation of the equilibrium compositions in the ER. In addition, a sensitivity study was performed on the effect of specific unknown activity coefficients—including sodium in molten cadmium, zirconium in molten cadmium, and sodium chloride in molten LiCl-KCl. Both computational methods produced identical results, which stayed within the 95% confidence interval of the experimental data. Furthermore, sensitivity to unavailable activity coefficients was found to be low (a change in concentration of less than 3 ppm).

SELECTIVE REDUCTION OF ACTIVE METAL CHLORIDES FROM MOLTEN LiCl-KCl USING LITHIUM DRAWDOWN

Simpson, Michael F.,Yoo, Tae-Sic,Labrier, Daniel,Lineberry, Michael,Shaltry, Michael,Phongikaroon, Supathorn Korean Nuclear Society 2012 Nuclear Engineering and Technology Vol.44 No.7

In support of optimizing electrorefining technology for treating spent nuclear fuel, lithium drawdown has been investigated for separating actinides from molten salt electrolyte. Drawdown reaction selectivity is a major issue that requires investigation, since the goal is to remove actinides while leaving the fission products and other components in the salt. A series of lithium drawdown tests with surrogate fission product chlorides was run to obtain selectivity data with non-radioactive salts, develop a predictive model, and draw conclusions about the viability of using this process with actinide-loaded salt. Results of tests with CsCl, $LaCl_3$, $CeCl_3$, and $NdCl_3$ are reported here. Equilibrium was typically achieved in less than 10 hours of contact between lithium metal and molten salt under well-stirred conditions. Maintaining low oxygen and water impurity concentrations (<10 ppm) in the atmosphere was observed to be critical to minimize side reactions and maintain stable salt compositions. An equilibrium model has been formulated and fit to the experimental data. Good fits to the data were achieved. Based on analysis and results obtained to date, it is concluded that clean separation between minor actinides and lanthanides will be difficult to achieve using lithium drawdown.