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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.
SELECTIVE REDUCTION OF ACTIVE METAL CHLORIDES FROM MOLTEN LiCl-KCl USING LITHIUM DRAWDOWN
MICHAEL F. SIMPSON 한국원자력학회 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, LaCl3, CeCl3, and NdCl3 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 (<10ppm) 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.
Simpson, Michael F.,Sachdev, Prateek Korean Nuclear Society 2008 Nuclear Engineering and Technology Vol.40 No.3
The results of process development for the blending of waste salt from the electrorefining of spent fuel with zeolite-A are presented. This blending is a key step in the ceramic waste process being used for treatment of EBR-II spent fuel and is accomplished using a high-temperature v-blender. A labscale system was used with non-radioactive surrogate salts to determine optimal particle size distributions and time at temperature. An engineering-scale system was then installed in the Hot Fuel Examination Facility hot cell and used to demonstrate blending of actual electrorefiner salt with zeolite. In those tests, it was shown that the results are still favorable with actinide-loaded salt and that batch size of this v-blender could be increased to a level consistent with efficient production operations for EBR-II spent fuel treatment. One technical challenge that remains for this technology is to mitigate the problem of material retention in the v-blender due to formation of caked patches of salt/zeolite on the inner v-blender walls.
MICHAEL F. SIMPSON,PRATEEK SACHDEV 한국원자력학회 2008 Nuclear Engineering and Technology Vol.40 No.3
The results of process development for the blending of waste salt from the electrorefining of spent fuel with zeolite-A are presented. This blending is a key step in the ceramic waste process being used for treatment of EBR-II spent fuel and is accomplished using a high-temperature v-blender. A labscale system was used with non-radioactive surrogate salts to determine optimal particle size distributions and time at temperature. An engineering-scale system was then installed in the Hot Fuel Examination Facility hot cell and used to demonstrate blending of actual electrorefiner salt with zeolite. In those tests, it was shown that the results are still favorable with actinide-loaded salt and that batch size of this v-blender could be increased to a level consistent with efficient production operations for EBR-II spent fuel treatment. One technical challenge that remains for this technology is to mitigate the problem of material retention in the v-blender due to formation of caked patches of salt/zeolite on the inner v-blender walls.
Basis for a Minimalistic Salt Treatment Approach for Pyroprocessing Commercial Nuclear Fuel
Simpson, Michael F.,Bagri, Prashant Korean Radioactive Waste Society 2018 방사성폐기물학회지 Vol.16 No.1
A simplified flowsheet for pyroprocessing commercial spent fuel is proposed in which the only salt treatment step is actinide drawdown from electrorefiner salt. Actinide drawdown can be performed using a simple galvanic reduction process utilizing the reducing potential of gadolinium metal. Recent results of equilibrium reduction potentials for Gd, Ce, Nd, and La are summarized. A description of a recent experiment to demonstrate galvanic reduction with gadolinium is reviewed. Based on these experimental results and material balances of the flowsheet, this new variant of the pyroprocessing scheme is expected to meet the objectives of minimizing cost, maximizing processing rate, minimizing proliferation risk, and optimizing the utilization of geologic repository space.
Shaltry, Michael R.,Allahar, Kerry N.,Butt, Darryl P.,Simpson, Michael F.,Phongikaroon, Supathorn Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.1
Molten salt solutions consisting of eutectic LiCl-KCl and concentrations of samarium chloride (0.5 to 3.0 wt%) at 500℃ were analyzed using both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV technique gave the average diffusion coefficient for Sm<sup>3+</sup> over the concentration range. Equipped with Sm<sup>3+</sup> diffusion coefficient, the Randles-Sevcik equation predicted Sm<sup>3+</sup> concentration values that agree with the given experimental values. From CV measurements; the anodic, cathodic, and half-peak potentials were identified and subsequently used as a parameter to acquire EIS spectra. A six-element Voigt model was used to model the EIS data in terms of resistance-time constant pairs. The lowest resistances were observed at the half-peak potential with the associated resistance-time constant pairs characterizing the reversible reaction between Sm<sup>3+</sup> and Sm<sup>2+</sup>. By extrapolation, the Voigt model estimated the polarization resistance and established a polarization resistance-concentration relationship.
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.
Jeong, Kwang Ho,Lee, Hyeon Jeong,Simpson, Michael F.,Jeong, Sang Mun American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5
<P>Graphene/MnO2 nano-composite was electrochemically synthesized for application to an electrode material for electrochemical supercapacitors. The nanosized needle-like MnO2 was obtained by use of a graphene substrate. The prepared composite exhibited an ideal supercapacitive behavior. A capacitance retention of 94% was achieved with a 4 h deposition time (an initial capacitance of 574 mF/cm(2) at a scan rate of 20 mV/s) and the retention declined with further deposition time. The results demonstrate enhanced contact between the electrode and electrolyte and improved power density as an electrochemical capacitor.</P>
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