金属乏燃料干法后处理熔盐电解槽电场分析

Analysis of Electric Field on Metallic Spent Fuel Pyroprocessing Molten Salt Electrorefining Cell

  • 摘要: 为支持乏燃料熔盐电解精炼设备的放大设计与优化,基于Maxwell原理和电化学理论,采用Comsol Multiphysics有限元方法,研究建立了10 kg/批次金属乏燃料熔盐电解精炼设备纯电场和电化学场数值模型,并对国外相对成熟的方形电解槽和圆台形电解槽进行了数值仿真分析和比较,包括电解槽结构、电极间距、阴极形状等因素对电解槽电场和电化学性能的影响。结果表明,方形电解槽的电流效率等经济性能较优,圆台形电解槽的反应电流密度等电化学性能较优;方形电解槽中,平板阴极的电流效率等经济性能和电化学性能均优于棒状阴极;电极间距在10~40 mm的研究范围内,两种电解槽的反应电流密度等电化学性能随电极间距的增大变化均不明显,但电解槽的电流效率等经济性能和热稳定性显著减弱。模拟结果与文献实验结果吻合良好,所建模型预期可较好反映熔盐电解精炼过程。

     

    Abstract: To assist the development of scientific research prototype and engineering prototype of melten salt electrorefining equipment, electric field analysis was carried out. By using Comsol Multiphysics software, a mathematical model of electric field and electrochemical field in 10 kg/batch uranium metal spent fuel pyroprocessing molten salt electrorefining cell was built based on Maxwell principle and electrochemical theory, under the condition of constant input current density. The effects of the electrorefining cell structure, electrode distance and cathode shape on the cell electric field and electrochemical performance were studied. The simulation results show that for the PEER square cell, the energy consumption is low, current efficiency is high and economic performance is excellent. For the highthroughput frustum cone cell, the current density is high, the electrochemical current density distribution of cathode is concentrated on the anode side, the uranium deposition morphology is uniform, and the electrochemical performance is excellent. For the flat-plate cathode square cell, the current density and current efficiency are high, electrochemical dissolution and deposition rate of uranium is fast, the economic performance and electrochemical performance are excellent. For the rod cathode square cell, the energy consumption is low, the electrochemical current density distribution of cathode is concentrated on the anode side, and the uranium deposition morphology is uniform. Within the range of this study, with the increase of electrode distance, the electric field intensity of the electrolytic cell increases, the mass transfer rate of uranium ions in molten salt increases, the electrochemical anode current density increases, the electrochemical current density of high-throughput frustum cone cell increases, and the electrochemical performance of the cell is almost unchanged. But with the increase of electrode distance, the cell voltage increases, the absolute value of electrode overpotential increases, the total cathode current density decreases, the total anode current density increases, the uniformity of thermal field temperature distribution decreases, the electrochemical cathode current density of PEER square cell decreases, the current efficiency decreases, and the economic performance and thermal stability of the electrolytic cell weaken. The simulation calculated values are in good agreement with the experimental data abroad, which indicates that the model can wholly embody the uranium metal molten salt electrorefining test practice. Taking the above factors into consideration, the high-throughput frustum cone cell with parallel-plate cathode and short spaced electrodes may be the cell with the best technical and economic indicators of electric field and electrochemical field. And it should be selected according to the requirements and process conditions in actual test and application.

     

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