基于相场方法的铀枝晶生长电化学-流场耦合研究

铀枝晶生长是导致乏燃料后处理电解精炼装置发生意外短路的潜在威胁因素,同时会使铀产物夹杂大量熔盐,影响产物纯度。为了更好地理解铀枝晶生长的微观机理,掌握阴极沉积形貌的控制方法,基于相场方法建立了铀在阴极的电沉积模型,研究了铀枝晶的底部沉积宽度、主枝晶干高度和总沉积面积等形貌参数对流场速度变化的依赖规律。发现外加流场的引入会使铀枝晶的底部沉积宽度降低37.18%,主枝晶干高度降低30.5%,总沉积面积降低49.3%。说明外加流场可以抑制铀枝晶生长,改善铀沉积形貌,但同时也会使破碎的枝晶须重新溶解到熔盐体系中,降低铀电解精炼效率。另外,通过对流场与电解电压、初始浓度等沉积条件耦合影响下铀枝晶形貌特征相图的分析可知,在实际电解精炼过程中,应在保证电解精炼效率的基础上尽量选择高初始浓度和高电解电压的沉积条件,同时设置合理的流场速度以获得理想的铀枝晶沉积形貌。     

无机氯化物熔盐在乏燃料干法后 处理中的应用进展

综述了无机氯化物熔盐在乏燃料后处理中的应用进展,主要介绍了LiCl-KCl熔盐在金属乏燃料中的电解精炼和熔剂萃取、LiCl-Li2O在金属氧化物或混合金属氧化物（MOX）乏燃料中的电化学还原及NaCl-2CsCl在氧化物乏燃料电化学沉积中的应用进展。展望了中国无机氯化物熔盐在干法后处理中的应用前景及发展方向。     

高碳铬铁熔盐电解精炼制备低碳纯净铬铁

以NaCl?KCl熔盐为电解质、高碳铬铁为工作电极、钨丝为对极、Ag/AgCl为参比电极,在阳极电极电势为0.3 V (vs. Ag/AgCl)的恒压条件下一步熔盐电解高碳铬铁制备低碳纯净铬铁;通过方波伏安法研究了阴极铬铁沉积机理,对阴极电解产物进行了微观分析和物相表征. 结果表明,阴极铬离子沉积是由扩散控速的一次性得失2个电子的可逆反应,且阳极中金属铬先于铁氧化进入熔盐;低碳铬铁合金为粒径0.5?2 ?m的球状颗粒,阴极产物低碳铬铁的碳含量仅为0.24wt%.     

基于有限元方法的CeCl3和NdCl3在LiCl-KCl熔盐中的电极动力学模拟

充分理解锕系元素和镧系元素在熔盐中的行为和性质是实现反应堆乏燃料熔盐电解后处理的关键,然而熔盐电解实验所需的高温环境、腐蚀性熔盐甚至放射性物质等条件限制了实验的广泛开展。为寻求一种低成本且可靠的获取元素在熔盐中性质的途径,采用有限元方法在不同温度下模拟了不同浓度的三氯化铈和三氯化钕在LiCl-KCl熔盐中的循环伏安曲线,并与实验数据做了对比。结果表明,有限元方法能够较为准确地反映实际电化学过程,继而为乏燃料熔盐电解后处理提供数据支持。     

酸性镀铜添加剂的作用与浓度测定

本文采用转盘电极阳极溶出法测定了光亮酸性镀铜液中组合添加剂的最佳整平浓度,又用赫尔槽测定了最大光亮区浓度,结果与通常生产中的用量相符。添加剂对铜沉积过程的阻化效应随镀液中添加剂浓度的增大而增大。如果用转盘电极在极限电流的电位处,阴极沉积一定的时间,随后使沉积的铜薄层阳极溶解,此时阳极溶出电量 Q 阳与镀液中添加剂的浓度 C_添成线性关系,因此可用来定量测定镀液中添加剂的浓度。     

制造氟或三氟化氮的电解装置

本发明的任务在于提供一种通过电解含氟化氢的熔盐而制造氟或三氟化氮的电解装置,此电解装置的优点在于可进行电解,而即使在大电流密度下也不会出现阳极效应,而且不会发生阳极溶解。在本发明中,此任务通过下面的电解装置完成,所述电解装置通过施加1到1000A／dm^2的电流密度电解含氟化氢的熔盐以制造氟或三氟化氮,该电解装置以涂覆导电金刚石的电极作为阳极。     

氯化锂-氯化钾熔盐中二氧化铈的熔解还原

熔盐电解技术是乏燃料干法后处理的重要技术路线。以二氧化铈为氧化物乏燃料的模拟物,探索了氧化物乏燃料在氯化锂-氯化钾熔盐体系中的熔解问题,研究了各参数（温度、时间、流速等）对氯化反应的影响,成功使用液态锌阴极回收熔盐中低浓度的铈,通过真空减压蒸馏成功实现了铈-锌合金的分离,为乏燃料的干法后处理提供了有参考价值的基础数据。     

电解法水处理——Robinson Vivian Noel Edward．US 6800206，2004

本专利介绍的电解水处理方法是将一瞬时电流传送到一组或几组浸于水中的活性电极上，每组电极有一个牺牲电极(主要作为阳极)和一个惰性电极(主要作为阴极)组成。当牺牲电极作为阳极时，能产生溶解离子进入到水中，     

硝酸肼体系中U(VI)电解还原制备U(Ⅳ)工艺研究

乏燃料后处理PUREX流程中铀钚分离主要是采用四价铀U(Ⅳ)作为还原剂将有机相中的四价钚Pu(Ⅳ)还原为三价钚Pu(Ⅲ)进入水相,而六价铀U(VI)仍保留在有机相中,从而实现铀钚分离.电解还原法是目前制备U(Ⅳ)的主要工艺.在新型电解槽中探究了硝酸铀酰料液在电解槽中的停留时间、料液循环形式、阴阳极板面积比和电源布置方式对电解槽出口U(Ⅳ)质量浓度的影响,获得了各因素对电解还原性能的影响规律,并进行了1:1规模连续运行验证试验,为U(Ⅵ)电解还原在工程中的应用提供了重要的参考依据.     

电解臭氧水的生产方法Okubo,Noriaki 等（Shinko Plant Construction Co.,Ltd.,Japan）

用电解O3发生器产生O3。发生器中装有固体聚合物电解质膜，位于阳极和阴极之间，二个电极都与直流电源相接，水通过阳极侧水管道和阴极侧水管道进行电解，含有溶解SiO2和／或重金属的原水通过一软水装置并到达二个电极侧的水管道，当固体聚合物电解质膜被降解时，对电解O3发生器停止供水但不切断电流，     

Studies of a Liquid Anode for Plutonium Electrorefining

Abstract

We are developing a solvent anode as an alternate method for producing plutonium metal of high purity by an electrorefining process. Our goals are to produce metal of 99.98% purity with an anode residue containing less than 2% of the plutonium in the feed material. If we are successful, we will design and demonstrate a system utilizing semi-continuous and remotely controlled operations.

Establishing a solvent anode method should lead to improved yields and a substantial reduction in the amount of residues generated by the electrorefining process. The new method should be a viable pyrochemical technique for recovering both plutonium and uranium from spent reactor fuel.

Initially, the anode consists of a tantalum rod immersed in a pool of liquid cadmium at 740°C. Impure plutonium or a solid anode residue is in contact with the cadmium. As current passes through the anode, plutonium in the cadmium is oxidized and transfers into the molten salt as tripositive plutonium. More plutonium dissolves into the cadmium and the oxidation continues. The tripositive plutonium is carried through the salt to the cathode, where it is reduced to pure, liquid metal. This metal, which is heavier than the salt, drips from the cathode into an annulus between the anode and cathode compartments and forms a product ring.     

A study on the recovery of actinide elements from molten LiCl–KCl eutectic salt by an electrochemical separation

Pyroprocessing is a prominent way for the recovery of the long-lived elements from the spent nuclear fuel. Electrorefining is a key technology for pyroprocessing and generally composed of two recovery steps—deposition of uranium onto a solid cathode and the recovery of TRU (TRansUranic) elements. In this study, it was investigated on electrochemical separation of actinides to develop an actinide recovery system in a molten LiCl–KCl eutectic salt. In the electrorefining experiment, uranium was successfully separated from cerium. The effects of the anode material and the surface area were investigated during the electrolysis experiments for a more efficient electrorefining system. Anode potential decreased with an increasing anode surface area, however, an anode effect was observed in case of a complicated anode structure for high surface area. Glassy carbon was found to be the best anode material among the molybdenum, graphite, glassy carbon, and oxide materials. It was found that the solid cathode with a perforated ceramic container could be one of the candidates for a salt clean-up process to remove residual actinide elements in the salt after the recovery step.     

Modeling the Molten Salt Electrorefining Process for Spent Metal Fuel Using COMSOL

Molten salt electrorefining process is one of the key steps of the pyrochemical reprocessing flow sheet for the spent metallic fuel from fast reactors. The electrorefining process is simulated using COMSOL Multiphysics. This involves solving multiple equations corresponding to electrochemical reactions at the electrode surfaces, mass transfer of metal ions in the electrolyte, potential distribution in the electrolyte, and overall material balance of metal ions in a coupled manner. The model is validated using the data of laboratory scale electrorefining experiments from literature. The results show a good agreement with the present experimental data, the variation being less than 10% for the U and Pu concentration changes in liquid Cd anode and molten salt, and U deposit on solid cathode.     

Behavior of diffusing elements from an integrated cathode of an electrochemical reduction process

The electrochemical reduction process for spent oxide fuel is operated in a molten salt bath and adopts an integrated cathode in which the oxides to be reduced act as a reactive cathode in the molten salt electrolyte cell. Heat-generating radioisotopes in the spent oxide fuel such as cesium and strontium are dissolved in the molten salt and diffuse from the integrated cathode. However, the behavior of the dissolved cations has not been clarified under an electrochemical reduction condition. In this work, the reduction potentials of cesium, strontium, and barium were measured in a molten LiCl-3 wt% Li₂O salt and their mass transfer behavior was compared with two current conditions on the cell. The concentration changes of the cations in the molten salt phase were measured and no significant differences on the dissolution behavior were found with respect to the current. However, under a continued current condition, the removal of the high heat-generating elements requires more time than the complete reduction of metal oxide due to the slow rate of diffusion.     

The recovery of chlorine from by-product hydrogen chloride Part 2: Molten metal cathode method

A new method of recovering chlorine from by-product hydrogen chloride is proposed and developed. According to the reaction Me+2HC1 = MeCl₂+H_o (Me = Metal) hydrogen chloride is reduced to give hydrogen and metal chloride. Gaseous hydrogen was drawn out from the reaction system and the metal chloride dissolved in the electrolyte, where it was electrolysed to give chlorine and metal using molten metal as a cathode. The metal was recovered on the cathode in a molten state and reused for the former reaction. Bench scale tests were also carried out, where zinc was used as a molten metal cathode and the cell capacity was about 50 A. The cell voltage was 6.5 V at 50 A (working temperature 560°C, distance between anode and cathode 5 mm) and in this case, the ohmic loss was about 70%. The current efficiency was about 90% (anodic current density 200 A/dm²) when the working temperature was 500°C and electrode distance between anode and cathode was 18 mm.This method seems very promising on the basis of the above-mentioned data.     

Predominance diagrams of uranium and plutonum species in both lithium chloride–potassium chloride eutectic and calcium chloride

Electro-reduction of spent nuclear fuel has the potential to significantly reduce the amount of high level waste from nuclear reactors. Typically, spent uranium and plutonium are recovered via the PUREX process leading to a weapons-grade recovery; however, electro-reduction would allow spent nuclear fuel to be recovered effectively whilst maintaining proliferation resistance. Here, we present predominance diagrams (also known as Littlewood diagrams) for both uranium and plutonium species in molten lithium chloride–potassium chloride eutectic (LKE) at 500 °C and in calcium chloride at 800 °C. All diagrams presented depict regions of stability of various phases at unit activity in equilibrium with their respective dissociated ions. The diagrams thermodynamically define the electrochemical system leading to predictions of reaction conditions necessary to electrochemically separate species. The diagrams have been constructed using a pure thermodynamic route; identifying stable species within the molten salt with an assumption of unit activity for each of the phases. These thermodynamically predicted diagrams have been compared to the limited available experimental data; demonstrating good correlation. The diagrams can also be used to predict regions of stability at activities less than unity and is also demonstrated.     

Formation of metal fog during molten salt electrolysis observed in a see-through cell

Visual observations of several molten salt electrolysis processes were made in a two-compartment, see-through quartz cell. The electrolyses of aluminium, magnesium, lead, zinc, sodium and potassium were studied. The colour of the melt in the anode compartment was pale yellow for fluoride-chloride melts and red for chloride melts, caused by the presence of dispersed anode gases during electrolysis. In the cathode compartment, streamers of metal fog were formed. The colours of the metal fog were purple for aluminium, grey for magnesium, lead and zinc, blue for sodium and green for potassium.The metal fog tended to sink to the bottom of the cell, which indicated that it had a higher density than that of the melt. The metal fog also penetrated into the anode compartment, probable due to convection and diffusion in the melt. The most probable explanation of the nature of the metal fog is that it consisted ofdispersed metal particles. This chemically unstable phase dissolved easily in the melt and was oxidized quickly by the anode gases.     

The electro-deoxidation of porous titanium dioxide precursors in molten calcium chloride under cathodic potential control

A study on the electro-deoxidation of porous titanium dioxide precursors in molten calcium chloride is reported. Experiments were performed with a three-terminal electrochemical cell, comprising a molten salt electrolyte of calcium chloride with additions of calcium oxide, a cathode of compact titanium dioxide with a significant degree of open porosity, as well as a graphite anode and a graphite pseudo-reference electrode. Reductions were carried out under cathodic potential control and at different applied potentials. The results reveal that the formation of titanium metal occurs at electrode potentials significantly more positive than that of calcium deposition, whilst the realisation of very low residual oxygen contents requires potentials around that of calcium deposition. It is demonstrated that oxygen contents in the titanium metal prepared of below 5000 ppm by mass may be achieved reproducibly within processing times of 16 h and at current efficiencies between 10 and 40%. The kinetic pathway is investigated, by analysing the compositions of samples prepared at different cathode potentials, and compared against the results from foregoing studies. It is found that the presence of calcium oxide in the calcium chloride accelerates the overall rate of electro-deoxidation, and that the temporary occurrence in the cathode of the calcium-containing compounds calcium titanate, CaTiO₃, and calcium titanite, CaTi₂O₄, are inherent features of the reaction path. The overpotential at the anode is shown to be of significant magnitude.     

Cu-Ce-Zr-O／YSZ阳极材料以甲烷为燃料时的抗积炭性能

为研究甲烷在固体氧化物燃料电池中操作稳定性,分别采用共沉淀法和柠檬酸溶胶.凝胶法制备了10%CuO-Ce0.15Zr0.85O2催化剂,并以此为阳极催化剂、LSM为阴极制成了YSZ电解质支撑的SOFC单电池.用XRD对材料进行表征;用SEM对阳极,阴极进行表征.以甲烷为燃料对单电池发电性能进行测试,研究了两种不同方法制备的Cu-Ce-Zr-O阳极催化剂的抗积炭性能.相对于共沉淀法,溶胶-凝胶法制备的阳极结构和发电性能都要优于前者.长期稳定性方面,共沉淀法和溶胶.凝胶法制备的Cu-Ce-Zr-O/YSZ阳极都较传统的Ni-YSZ阳极更能够长期稳定运行.