乏燃料干法和水法后处理设施经济性分析

核燃料循环是影响核电经济评价的重要因素,是推进核能发展的关键问题。乏燃料后处理作为核燃料循环后段的重要组成部分,其经济成本会影响整体的核燃料循环成本。为对核燃料循环尤其是后段循环成本的分析提供更准确参考,本文调研了国外干法和水法后处理设施的经济性数据,并结合对快堆乏燃料后处理设施的经济性研究,进行了热堆和快堆乏燃料的干法和水法后处理成本的分析,给出了各设施的后处理成本数据。     

乏燃料后处理技术研究现状

主要针对水法、干法和超临界流体萃取等三种乏燃料后处理技术的特点、国内外研究现状进行了综述,并指出从长远来看,先进反应堆乏燃料处理倾向于利用干法后处理技术,在乏燃料后处理/分离一体化水法后处理流程中倾向于采用超临界流体萃取后处理技术。     

机器人技术在乏燃料后处理自动化分析中的应用

介绍了机器人技术在国内外乏燃料后处理自动化分析中的应用进展,阐述了当前面临的问题,为今后机器人技术在我国后处理分析领域的应用和发展提供参考.     

高温氯化物熔盐中使用的Ag/AgCl参比电极研究进展

综述了用于高温氯化物熔盐体系的Ag/Ag Cl参比电极的研究进展,阐述了熔盐Ag/Ag Cl参比电极常见结构及制作过程,总结了影响电极稳定性和重现性的主要因素如隔膜材质(Pyrex玻璃、石英、刚玉和莫来石)、H2O及Ag Cl含量等,展望了高温氯化物熔盐中的Ag/Ag Cl参比电极未来发展趋势。     

含钙三元氯化物体系相图计算与熔盐热稳定性

为寻求太阳能热利用高温传热储热材料,以盐湖资源为原料,提出分支/分区相图计算方法,设计NaCl-CaCl₂-KCl和KCl-CaCl₂-MgCl₂熔盐传热储热材料。基于正规溶液模型,以不同分支不同相互作用系数,计算了5个边界体系相图,实现用正规溶液模型计算含化合物体系复杂相图。含化合物KCl-CaCl₂和KCl-MgCl₂体系及3个不含化合物二元体系的计算相图与实验相图十分吻合。以分区域方法计算三元体系相图,预测出5个低共熔点来指导熔盐制备。采用差示扫描量热法测试并验证熔盐最低共熔点,确定其工作温度下限;以质量损失实验,确定其工作温度上限。结果表明,钠钾钙和钾镁钙氯化物熔盐能在550~850℃和480~700℃内稳定运行,可用作高温传热储热流体。     

氯化物熔盐中铬的价态对镍基合金腐蚀性的影响

氯化物熔盐的腐蚀性是制约其应用的重要因素,对富铬金属材料的腐蚀会导致金属中铬元素优先流失到熔盐中。探讨进入熔盐中不同价态的铬对后续腐蚀的影响,是了解熔盐长期运行中金属持续受腐蚀的关键。通过浸没腐蚀实验研究在三元NaCl-MgCl₂-CaCl₂熔盐中引入Cr⁰、Cr²⁺与Cr³⁺后,对一种贫铬Hastelloy B-2(HB-2)和两种富铬Hastelloy C-276(HC-276)、Hastelloy X(HX)镍基合金腐蚀性的影响。通过比较腐蚀前后质量变化、X射线衍射(XRD)、扫描电子显微镜(SEM)以及能谱分析(EDS)的结果,探讨含不同价态铬的熔盐对贫铬与富铬金属的腐蚀性差异。实验结果表明,Cr⁰和Cr²⁺能消耗熔盐中H₂O、O₂等氧化性物种,从而有效抑制腐蚀;Cr³⁺会抑制贫铬HB-2的腐蚀,但能促进富铬HC-276和HX的腐蚀;SEM和XRD分析结果表明,Cr³⁺在增强富铬金属铬优先流失的同时也会增强铁流失。热力学理论计算结果表明,CrCl₃氧化Cr、Fe的反应进行得很彻底;而CrCl₃氧化Ni、Mo的反应进行程度有限。因此,熔盐中含CrCl₃会氧化合金中Cr和Fe从而促进富铬合金腐蚀,而含Cr⁰和CrCl₂能降低熔盐中的氧化性物质含量而抑制腐蚀。     

氯化物熔盐中铬的价态对镍基合金腐蚀性的影响

氯化物熔盐的腐蚀性是制约其应用的重要因素,对富铬金属材料的腐蚀会导致金属中铬元素优先流失到熔盐中。探讨进入熔盐中不同价态的铬对后续腐蚀的影响,是了解熔盐长期运行中金属持续受腐蚀的关键。通过浸没腐蚀实验研究在三元NaCl-MgCl₂-CaCl₂熔盐中引入Cr⁰、Cr²⁺与Cr³⁺后,对一种贫铬Hastelloy B-2(HB-2)和两种富铬Hastelloy C-276(HC-276)、Hastelloy X(HX)镍基合金腐蚀性的影响。通过比较腐蚀前后质量变化、X射线衍射(XRD)、扫描电子显微镜(SEM)以及能谱分析(EDS)的结果,探讨含不同价态铬的熔盐对贫铬与富铬金属的腐蚀性差异。实验结果表明,Cr⁰和Cr²⁺能消耗熔盐中H₂O、O₂等氧化性物种,从而有效抑制腐蚀;Cr³⁺会抑制贫铬HB-2的腐蚀,但能促进富铬HC-276和HX的腐蚀;SEM和XRD分析结果表明,Cr³⁺在增强富铬金属铬优先流失的同时也会增强铁流失。热力学理论计算结果表明,CrCl₃氧化Cr、Fe的反应进行得很彻底;而CrCl₃氧化Ni、Mo的反应进行程度有限。因此,熔盐中含CrCl₃会氧化合金中Cr和Fe从而促进富铬合金腐蚀,而含Cr⁰和CrCl₂能降低熔盐中的氧化性物质含量而抑制腐蚀。     

氯化物熔盐材料的制备及其热物理性质研究

制备了NaCl-CaCl₂、 NaCl-KCl-CaCl₂、 NaCl-CaCl₂-MgCl₂、 KCl-CaCl₂-MgCl₂、 NaCl-KCl-MgCl₂、 NaClKCl-CaCl₂-MgCl₂六种氯化物熔盐材料。采用差示扫描量热法确定它们的低共熔点和组成,测量其比热容、密度、黏度等热物性。测试熔盐材料的质量损失曲线确定工作温度上限,根据测试的结果,对其储能密度进行计算。研究结果表明:NaCl-KCl-CaCl₂-MgCl₂熔盐材料熔点为380.3℃,流动性较好,工作温度范围为430～700℃,储能密度为625.1 J·cm^-3,是六种熔盐中熔点最低、储能密度最大的熔盐,适合作为传热储热材料。NaCl-KCl-CaCl₂熔盐熔点为503.8℃,工作温度范围为550～850℃,储能密度为559.9 ...     

乏燃料后处理中氪-85处理技术研究

针对核反应堆乏燃料后处理工艺过程中氪-85同位素处理需求,本文系统地分析了吸附法、低温精馏法和溶剂吸收法三种分离方法,三种分离方法均能有效的从溶解尾气中脱除氪,极大地降低乏燃料后处理厂放射性气体流出物的排放。结合三种分离方法在国际上的工程实际应用案例分析,详细的比较论述了各种分离方法的优势与不足;结合氪-85同位素的储存技术,认为低温精馏法为具有广泛应用前景的处理技术。     

Electrochemical nucleation of uranium in molten chlorides

The electrochemical nucleation of uranium in molten salts on vitreous carbon was studied using chronoamperometry. It is shown that, whatever the applied overpotential and the temperature of the melt, the nucleation of uranium is instantaneous, three-dimensional and controlled by hemispherical diffusion. The diffusion coefficient of UIII is calculated. The value obtained by chronoamperometry is in good agreement with that obtained by cyclic voltammetry in previous studies [1].     

乏燃料熔盐电解后处理动力学模型研究

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。     

Electrochemical reduction of trivalent uranium ions in molten chlorides

The electrochemical behaviour of UIII in molten salts was studied at 715 C under argon atmosphere in a molten equimolar NaCl–KCl mixture containing uranium ions in oxidation state III (UCl3). Three different complementary electrochemical methods were used, namely cyclic voltammetry, chronopotentiometry and square wave voltammetry. These techniques provide data to explain the electroreduction mechanism. The reduction of UIII in the NaCl–KCl mixture occurs in a single step with an exchange of three electrons, this process is controlled by the diffusion of UIII. The diffusion coefficient of U(III) was calculated using the three electrochemical methods.     

Determination of diffusion coefficients of depositing ions in molten chlorides by transient electrochemical techniques

The electrochemical reduction of Pb(II), Zn(II) and Mg(II) ions at glassy carbon and tungsten electrodes in molten KCl–LiCl eutectic was studied by linear sweep voltammetry (LSV), convolutive potential sweep voltammetry (CPSV), chronopotentiometry and chronoamperometry. In the case of lead deposition, the initial nucleation stage was found to influence the shape of the voltammetric current peak. CPSV was consequently believed to be a more reliable method than LSV for the calculation of the diffusion coefficient of the Pb(II) ion. Similar complications were not observed for zinc and magnesium since the nucleation overpotentials for these metals were significantly lower than for lead. On the other hand, lithium codeposition made it difficult to interpret the zinc and especially the magnesium convolution voltammograms. Chronopotentiometry yielded practically identical results for D _Pb(II) as the voltammetric techniques. However, due to a substantial residual current, the Sand equation was not obeyed for the Zn(II) and Mg(II) ions. Determination of diffusion coefficients from single potentiostatic current transients and the Cottrell equation was not found to be a very reliable method. Empirical expressions for the temperature dependence of D in the range 400–500 °C were calculated for all three ions.     

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。     

Graphite intercalation compounds of lanthanide metals prepared in molten chlorides

Graphite intercalation compounds of several lanthanide metal donors (Nd, Sm, Dy, Er and Yb) have been prepared by interacting graphite and metals in molten chlorides. These lanthanide metals are suspended in molten chlorides at lower than 400 °C in the presence of their trichlorides via disproportionation equilibrium: 3Ln(II) = Ln(0) + 2Ln(III). In this condition, one can avoid the formation of carbides in the reaction product. The X-ray powder diffraction patterns for all the lanthanide GICs prepared suggest they belong to the hexagonal EuC₆-structure type.     

熔融盐高储热材料的研究进展

储热技术是太阳能热发电行业的关键技术,而熔融盐是储热行业的主导材料。对储热材料的概念和类型做了介绍。概述了太阳能热发电在国内外的发展趋势,对比了碳酸盐、氯化盐、硝酸盐作为储热材料的优缺点,重点综述了熔融盐及其与其他材料（如金属、膨胀石墨、陶瓷等）的复合熔盐的研究进展,提出了避免孤立研究储热材料和开发多种复合技术的新思路。     

Predicting chemical reaction equilibria in molten carbonate fuel cells via molecular simulations

It has been recently suggested that hydroxide ions can be formed in the electrolyte of molten carbonate fuel cells when water vapor is present. The hydroxide can replace carbonate in transporting electrons across the electrolyte, thereby reducing the CO₂ separation efficiency of the fuel cell although still producing electricity. In this work, we obtain the equilibrium concentration of hydroxide in five molten alkali carbonate salts from molecular simulations. The results reveal that there can be a substantial amount of hydroxide in the electrolyte at low partial pressures of CO₂ . In addition, we find that the equilibrium concentration of molecular water dissolved in the electrolyte is over two orders of magnitude higher than that of CO₂ . Increasing the size and polarizability (or in other words reducing the “hardness”) of the cations present in the electrolyte can reduce the hydroxide fraction, but at the cost of lowering ionic conductivity.