共查询到20条相似文献,搜索用时 31 毫秒
1.
随着快堆研究的快速发展,干法后处理工艺流程也逐渐成为了研究重点,熔盐电解干法后处理是未来先进核燃料循环系统的核心环节和关键技术。氯化锂-氯化钾共晶盐是干法后处理工艺中最常用的熔盐体系。为了提取乏燃料中的锕系、镧系和铯、锶元素,需要对熔盐进行长时间的电解。在锕系分离提取过程中,镧系和铯、锶等活泼裂片元素在熔盐中不断积累,不仅会改变熔盐体系的理化性质,还将影响后续锕系产品的净化效果。为实现溶剂盐复用,使放射性废物最小化,需定期对废熔盐中的镧系和铯、锶等活泼裂片元素进行净化处理。对干法后处理氯化锂-氯化钾废熔盐中镧系和铯、锶等活泼裂片元素采取的净化工艺,包括熔盐萃取法、熔盐电解法、沉淀法、区域精炼法等工艺的原理、特点和研发进展进行了综述和比较分析,讨论了上述工艺中为实现溶剂盐复用、减少放射性废物产生对废熔盐中的镧系和铯、锶等活泼裂片元素的净化效果。指出了中国废盐净化将围绕实现稀土资源利用最大化、保护环境、最大程度上减少废物的排放开展相关方向的研究。 相似文献
2.
《分离科学与技术》2012,47(10):1965-1983
Abstract Bench‐scale tests were performed to study an electrolytic reduction process that converts metal oxides in spent nuclear fuel to metal. Crushed spent oxide fuel was loaded into a permeable stainless steel basket and submerged in a molten salt electrolyte of LiCl–1 wt% Li2O at 650°C. An electrical current was passed through the fuel basket and a submerged platinum wire, effecting the reduction of metal oxides in the fuel and the formation of oxygen gas on the platinum wire surface. Salt and fuel samples were analyzed, and the extent of fission product separation and metal oxide reduction was determined. 相似文献
3.
电解精炼是乏燃料干法后处理工艺中的关键环节。针对氯化锂-氯化钾(LiCl-KCl)熔盐环境中的电解精炼行为,基于电极表面处的反应过程建立了动力学模型。通过与现有实验数据的比较验证了模型的有效性。通过该模型,可以预测电解精炼过程中液镉阳极中乏燃料的溶解和阴极处金属沉积的动力学特征,以及所涉及元素的分电流、电极电位和熔盐中离子浓度的演变。除此之外,该模型还能模拟多元素复杂体系电解精炼的过程。当使用锆、铀、钚及稀土作为阳极时,模拟结果显示在阳极处锕系元素和稀土元素随时间逐渐溶解,而惰性金属几乎不溶解。在熔盐中,钚的浓度逐渐增加而铀的浓度逐渐减少,当钚开始在固体阴极发生沉积后,铀的沉积速率减小,而稀土元素和锆在阴极的沉积量极少。 相似文献
4.
《分离科学与技术》2012,47(9-10):2709-2721
Abstract Electrochemical processing technology is currently being used for the treatment of metallic spent fuel from the Experimental Breeder Reactor-II at Idaho National Laboratory. The treatment of oxide-based spent nuclear fuel via electrochemical processing is possible provided there is a front-end oxide reduction step. During this reduction process, certain fission products, including Cs and Sr, partition into the salt phase and form chlorides. Both solid state and molten LiCl-zeolite-A ion exchange tests were conducted for selectively removing Cs and Sr from LiCl-based salt. The solid-state tests produced in excess of 99% removal of Cs and Sr. The molten state tests failed due to phase transformation of the zeolite structure when in contact with the molten LiCl salt. 相似文献
5.
Michele A. Lewis Donald F. Fischer Londa J. Smith 《Journal of the American Ceramic Society》1993,76(11):2826-2832
The pyrometallurgical processing of spent fuel from the integral fast reactor (IFR), an advanced reactor under development at Argonne National Laboratory, will generate a chloride salt waste containing the alkali-metal, alkaline-earth, and some of the rare-earth fission products. Salt-occluded zeolite A, formed by equilibrating simulated molten waste salt and zeolite A, has been investigated as an immobilization matrix for this salt waste. In this concept, the chloride waste salt is loaded into the zeolite cavities, and cesium and strontium from the salt are preferentially sorbed by the zeolite. Experiments showed that the salt-occluded zeolite powders are leach resistant and radiation stable. The conclusion is that the salt-occluded zeolite is a promising immobilization matrix for the IFR waste salt. 相似文献
6.
Reyna Famila Descallar-Arriesgado Naoto Kobayashi Tatsuya Kikuchi Ryosuke O. Suzuki 《Electrochimica acta》2011,(24):8422
Metallic nickel powders with low and uniform residual oxygen content were produced from NiO using the molten salt electrolysis of CaO in CaCl2 melt. Suitable amount of CaO for the reduction was in the range of 0.5–3.0 mol% CaO.The electrical isolation of NiO from both electrodes could produce metallic Ni in CaCl2 melt. Separating the metal oxides from the cathode confirmed the mechanism of calciothermic reduction that the electrolysis of dissolved CaO in CaCl2 melt produces Ca, and that the dissolved Ca in molten CaCl2 successfully reduces NiO to metallic Ni. An average of about 600 ppm oxygen in Ni sample was achieved directly from oxide, when NiO was detached from the cathode. 相似文献
7.
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。 相似文献
8.
9.
La0.8Sr0.2MnO3 was coated on porous NiO cathode using a simple combustion process. X-ray diffraction (XRD) and scanning electron microscopy
(SEM) were employed in the cathode characterizations. The electrochemical behavior of La0.8Sr0.2MnO3-coated NiO cathodes (LSM–NiO) were also evaluated in a molten 62 mol%Li2CO3+38 mol%K2CO3 eutectic at 650 °C under the standard cathode gas condition by electrochemical impedance spectroscopy (EIS). The impedance
response of the NiO and LSM–NiO cathode at different immersion times is characterized by the presence of depressed semicircles
in the high frequency range and an extension at low frequencies. Impedance analysis showed that the behavior of the developed
cathode was similar to that of the conventional nickel oxide cathode. The LSM–NiO showed a lower dissolution and a better
catalytic efficiency superior to the state-of-the-art NiO value. Thus the cathode prepared with coating method to coat La0.8Sr0.2MnO3 on the surface of NiO cathode is able to reduce the solubility of NiO to lengthen the lifetime of MCFC while maintaining
the advantages of NiO cathode. The LSM–NiO shows promise as an alternate cathode in molten carbonate fuel cells (MCFCs). 相似文献
10.
C. Christenn G. Steinhilber M. Schulze K. A. Friedrich 《Journal of Applied Electrochemistry》2007,37(12):1463-1474
The cathode catalysts in low temperature fuel cells are associated with major cell efficiency losses, because of kinetic limitations
of the oxygen reduction reaction. Additionally, methanol oxidation at the cathode leads to significant lowering of the efficiency
in direct methanol fuel cells, which can be alleviated by use of methanol-tolerant catalysts. In this work, alternative carbon-supported
platinum-alloy catalysts were investigated by physical methods. Second, methanol-tolerant ruthenium-selenide catalysts were
characterized by physical and electrochemical methods. Besides V–i characteristics and electrochemical impedance spectroscopy as electrochemical methods, physical methods such as X-ray photoelectron
spectroscopy, nitrogen adsorption, porosimetry by mercury intrusion and temperature programmed reduction are used to characterize
the catalysts. The electrochemical characterization yields information about properties and behavior of the catalyst. In contrast
to platinum a significantly different hydrophobic behavior of the RuSe/C catalysts is found. Low open circuit voltage values
measured for RuSe/C indicate an effect on both electrodes. The anode reaction was also influenced by the different cathode
catalysts. As a result of the formation of H2O2 at the cathode, which passes through the membrane from cathode to anode side, a mixed anode potential is formed. By comparing
RuSe/C catalysts before and after electrochemical stressing, changes of the catalysts are determined. Postmortem surface analysis
(by X-ray photoelectron spectroscopy) revealed that catalyst composition and MEA structure changed during electrochemical
stressing. During fuel cell operation selenium oxide is removed from the surface of the catalysts to a large extent. Additionally,
a segregation effect of selenium in RuSe to the surface is identified. 相似文献
11.
12.
Subramanyan Vasudevan 《Korean Journal of Chemical Engineering》2009,26(5):1246-1251
The electrochemical preparation of strontium perchlorate, Sr(ClO4)2, from strontium chlorate employing platinum anode and a rotating stainless steel cathode is described. The effect of electrolyte
concentration, current density, pH and temperature of the electrolyte and cathode rotation on current efficiency for the preparation
of strontium perchlorate was studied. A maximum current efficiency of 42% was achieved corresponding to an energy consumption
of 6.1 kWh. kg−1. 相似文献
13.
Sang Woon Kwon Do Hee Ahn Eung Ho Kim Ho Geun Ahn 《Journal of Industrial and Engineering Chemistry》2009,15(1):86-91
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. 相似文献
14.
Many concerns have been raised about the mechanism of cathode reaction in molten carbonate fuel cell (MCFC). The chemical behavior of oxide species at cathode in molten carbonate is a key for understanding the process of cathode reactions. In this paper, the variety and role of the oxide species in both bulk and thin-film of basic molten carbonates were investigated by using a novel in-situ Raman spectroscopy. The results indicated that the dominant oxide species under basic conditions was peroxide ion, and it was possible to transform into the oxygen of crystalline lattice during the lithium-doped process. It was demonstrated that in-situ Raman spectroscopic technique was a promising tool to elucidate the mechanism of electrode reaction in molecular level in the MCFC condition. 相似文献
15.
A lanthanum strontium manganese thin oxide layer was plated on yttria stabilized zirconia by oxidizing the lanthanum strontium manganese ions with hydrogen peroxide as the oxidant. The plated oxide layer was firmly adherent to the substrate, and its morphology was finely porous. The crystal phase of the oxide was determined by XRD to be a perovskite-type. The mechanism for the oxide layer formation by an oxide electroless plating was studied by means of ESCA. As a cathode of solid oxide fuel cell (SOFC), the electrode characteristics of an oxide plated in this way were measured by the current interruption method at 1000° C. The cathodic overpotential of this electrode was less than 40 mV at 1 A cm–2 This small overvoltage was considered to be based on an effective large electrode reaction area. 相似文献
16.
The effect of magnetic field on the oxygen reduction reaction and its application in polymer electrolyte fuel cells 总被引:2,自引:0,他引:2
Tatsuhiro Okada Nobuko I. Wakayama Hiroshi Shingu Takeo Ozawa 《Electrochimica acta》2003,48(5):531-539
The effect of magnetic field gradients on the electrochemical oxygen reduction was studied with relevance to the cathode gas reactions in polymer electrolyte fuel cells. When a permanent magnet was set behind a cathode, i.e. platinum foil or Pt-dispersed carbon paper for both electrochemical and rotating electrode experiments and oxygen was supplied to the uphill direction of the magnetic field, electrochemical flux was enhanced and the current increased with increasing the absolute value of magnetic field. This magnetic effect can be explained by the magnetic attractive force toward O2 gas. When magnet particles were included in the catalyst layer of the cathode and the cathode was magnetized, the current of oxygen reduction was higher than that of nonmagnetized cathode. A new design of the cathode catalyst layer incorporating the magnet particles was tested, demonstrating a new method to improve the fuel cell performance. 相似文献
17.
《分离科学与技术》2012,47(15):2276-2283
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. 相似文献
18.
Compatibility Issues of Yttria‐Stabilized Zirconia Solid Oxide Membrane in the Direct Electro‐Deoxidation of Metal Oxides
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Abhishek Mukherjee Nicolo’ Campagnol Joris Van Dyck Jan Fransaer Bart Blanpain 《Journal of the American Ceramic Society》2015,98(3):972-981
Direct electro‐deoxidation of metal oxides has become quite popular in the production of metals and alloys. In this process, metal oxide cathode is directly reduced to a metal in a molten CaCl2 salt bath. The anode material used is graphite. Over the years, graphite is reported to cause numerous process difficulties. Recently, based on the solid oxide membrane technology, yttria‐stabilized zirconia (YSZ) has been tested as oxygen ion conducting membrane for the anode. The success of using a membrane implies its long‐term stability in the bath. In this paper, it is seen that YSZ chemically degrades in a static melt of CaCl2 or CaCl2–CaO. The degradation occurs by leaching of yttria into solution leading to the formation of monoclinic zirconia which, being porous, reacts with the molten electrolyte to form calcium zirconate. However, on application of voltage, YSZ degrades via a different mechanism. The metallic calcium produced during electrolysis increases the electronic conductivity of the salt, apparently leading to the electrochemical reduction of zirconia to ZrO2?x. As a result, localized pores are formed which allow the infiltration of salts. Addition of yttria to the salt is seen to prevent both the chemical and electrochemical degradation of the membrane. 相似文献
19.
《Journal of the European Ceramic Society》2020,40(10):3608-3617
This work focuses on a novel, co-sintered, all-ceramic solid oxide fuel cell (SOFC) concept. The objective is the understanding of interaction and degradation mechanisms of the cathode and current collector layers within the design during co-sintering. Half cells consisting of silicate mechanical support, lanthanum strontium manganite (LSM) current collector, LSM mixed with 8 mol% yttria-stabilized zirconia (8YSZ) composite cathode and 8YSZ electrolyte were co-sintered at 1150 °C < T < 1250 °C. Crystallographically stable LSM compositions within the design were identified. However, the cathode and silicate/electrolyte interacted by interdiffusion of Zn (gas diffusion) and Mn (solid diffusion), and by the formation of several reaction phases (between silicate and cathode only). Introducing silicate poisoning decreased the electrochemical performance of the cell by around 40%. This is likely due to the formation of the Zn- and Mn-rich phase in the cathode, but may also be caused by a higher ohmic resistance of the current collector. 相似文献
20.
A solid metal oxide cathode undergoes significant chemical changes during the molten salt electro-deoxidation process. The
changes in the chemical composition lead to changes in the electrical resistivity and potential of the electrode. Two novel
electrochemical techniques, based on these two parameters, have been employed to study the electro-deoxidation of solid TiO2 and ZrO2 in molten calcium chloride at 900 °C. The in situ resistance measurements carried out by the IR drop method conclusively
proved that TiO2 electrode remains highly conducting throughout the electro-deoxidation process and hence is amenable for reduction. The ZrO2 electrode, on the other hand, developed very high resistance midway in the electro-deoxidation, and could not be reduced
completely. The resistance measurements give strong indication that the electron-transfer reactions taking place at the cathode
determine the rate and efficiency of the electro-deoxidation process to a great extent. The low-current galvanostatic electro-deoxidation
of TiO2 electrodes, in conjunction with a graphite pseudo reference electrode to monitor the half cell potentials, showed that the
metal oxide passes through two stages during the electrolysis; a high current, low resistant stage 1, where Ca2+ ions are inserted to the metal oxide cathode to produce different intermediate compounds and stage 2 where electro-deoxidation
of the cathode take place continuously. Removal of oxygen, from the cathode, in stage 1 of the electro-deoxidation is considered
to be insignificant. The anodic and cathodic voltages in this stage remained more or less stable at ~1.4 V and ~−1 V, respectively.
When the oxygen ions in the melt were depleted at the end of this stage, both the anode and cathode potentials were increased
in the anodic direction and this behaviour suggested that the graphite pseudo reference electrode was changed from a C/CO
electrode in stage 1 to a Ca2+/Ca electrode in stage 2. 相似文献