熔盐中铀的电沉积

基于LiCl-KCl熔盐中铀离子的电化学行为研究结果，我们在LiCl-KCl-UCl3和LiCl-KCl-UCl3-UCl4两种熔盐中开展了铀的电沉积研究，旨在摸索沉积方法，并对沉积物的形貌及组成进行分析表征。     

干法后处理熔盐电解精炼过程数学模型研究

熔盐电解精炼是乏燃料干法后处理的核心工艺单元,通过数学模型探索高温熔盐电解精炼过程的化学与电化学变化,可为电解精炼工艺优化和设备设计提供参考依据。本文基于电化学热力学及物质传递公式建立了乏燃料熔盐电解精炼过程的数学模型,以铀钚锆三元合金燃料为研究对象,计算了燃料中关键元素的电极电势、分电流及物料分布随时间的变化。采用向后差分法对物料分布变化方程进行离散,通过文献实验数据对建立的数学模型进行了准确性验证。结果表明,模拟计算所得阴极沉积铀产品与实验数据的相对误差为2.80%,所建数学模型具有较好的拟合性。同时采用所建模型模拟计算了电流强度对乏燃料电解精炼过程的影响,结果表明电解速率与电流强度呈正比,不改变钚铀锆的溶解和沉积顺序。     

液体阴极法回收盐渣中钚离子的模拟实验

采用液体阴极法电解NaCl-KCl-CeCl_3熔盐,回收熔盐中的铈离子以模拟高温化学工艺废盐渣中钚离子的回收。研究了初始CeCl_3浓度、温度、阴极电流密度对电解指标的影响,确定了初始CeCl_3质量分数为5%、温度750℃、阴极电流密度0.10A/cm~2时,熔盐对Ce的净化系数可达130,盐渣中残留的CeCl_3质量分数可降低到0.04%以下。实验证实了液体阴极法有望应用于废盐渣中钚离子的回收。     

脉冲分子镀制备铀靶方法研究

采用脉冲电沉积方法, 以N,N-二甲基甲酰胺(DMF)体系为电镀介质,研究了电极距离、溶剂DMF的体积、沉积时间、铀的质量浓度、阴极材料等对镀层性能和铀沉积率的影响,得到在DMF中脉冲分子镀铀的最佳条件, 制备得到的靶面平整、牢固.用扫描电镜分析了铀靶的形貌和组成,采用测厚仪分析了铀靶厚度的均匀性.结果表明,在脉冲电沉积中,铀是非均匀沉积,靶面密度为0.2～2.0 mg/cm2.     

俄罗斯氧化物乏燃料电沉积流程研究进展

高温熔盐干法后处理以熔盐作为电解质，通过电解精炼和电沉积回收核燃料中的铀和钚。目前，俄罗斯、美国、日本、韩国和欧盟等国均在积极发展乏燃料高温熔盐干法后处理技术的研究，其中俄罗斯的金属氧化物核燃料电沉积流程是经典的流程之一。本文对俄罗斯原子反应堆研究所（Research Institute of Atomic Reactors,RIAR）发展的氧化物乏燃料高温熔盐电沉积干法后处理的发展现状、流程及特点进行了综述。     

LiCl-KCl-GaCl_(3)熔盐体系共沉积提取Sm的电化学北大核心CSCD

采用循环伏安法(CV)、方波伏安法(SWV)和开路计时电位法(OCP)等方法研究了LiCl-KCl熔盐中SmCl_(3)、GaCl_(3)和SmCl_(3)-GaCl_(3)在Mo阴极上的电化学行为。SmCl_(3)在Mo阴极上的电化学研究结果表明,Sm^(3+)在LiCl-KCl熔盐体系中发生单电子转移反应,仅能还原为Sm^(2+);并计算了不同温度下Sm^(3+)的扩散系数和Sm^(3+)/Sm^(2+)电对的表观标准电位。SmCl_(3)与GaCl_(3)共沉积电化学分析结果表明,Sm^(3+)还原为Sm^(2+)后,可与Ga形成SmGa_(x)合金化合物。X射线衍射和扫描电子显微镜与能谱分析(SEM-EDS)表明-1.600 V恒电位电解LiCl-KCl-SmCl_(3)-GaCl_(3)可得到SmGa_(2)合金。以上研究表明,加入GaCl_(3)可从LiCl-KCl-SmCl_(3)熔盐体系中有效提取Sm。     

自草酸铵介质中定量电沉积天然铀的研究

本文比较系统地报导有关电沉积制备0.0025—5毫克/厘米~2不同厚度的天然铀镀层的工作。我们就电沉积温度、阴极村料、铝阴极表面处理方法、阴极电流密度、电解波的pH值和铀浓度、电解时间等对电沉积产率的影响进行了研究,得出相应的结果,并提供了测定方法。此外,测定了不同放置时间的电沉积之组成得出电沉积组成与放置时间的关系。     

俄罗斯氧化物乏燃料电沉积流程研究进展

高温熔盐干法后处理以熔盐作为电解质,通过电解精炼和电沉积回收核燃料中的铀和钚。目前,俄罗斯、美国、日本、韩国和欧盟等国均在积极发展乏燃料高温熔盐干法后处理技术的研究,其中俄罗斯的金属氧化物核燃料电沉积流程是经典的流程之一。本文对俄罗斯原子反应堆研究所(Research Institute of Atomic Reactors, RIAR)发展的氧化物乏燃料高温熔盐电沉积干法后处理的发展现状、流程及特点进行了综述。     

铀、钚氧化物氯化溶解技术进展

氧化物的溶解过程是氧化物乏燃料熔盐电解干法后处理工艺的关键步骤,溶解产物将为后续铀钚的分离回收提供原料。氧化物在熔盐体系中溶解度和溶解速率一般较小,为满足工艺需要,通常需要引入氯化试剂。使用不同的氯化试剂,其溶解机理有较大差异。通过广泛的文献调研,分析比较了各种氯化试剂在氯化过程中相关原理及特点,为我国开展铀、钚氧化物氯化溶解的研究提供指导。     

熔盐快堆Th-U燃料循环增殖性能分析

熔盐快堆是当前国际上关注的热点之一,本文基于堆芯结构双流体方案,即裂变熔盐燃料和增殖熔盐介质各自独立冷却循环,利用氟化或氯化熔盐中钍铀重金属盐高温下的高溶解度特性,获得熔盐快堆的高增殖。通过比较钍铀燃料循环熔盐快堆的三种可行性熔盐燃料方案(LiF+ThF_4+UF_4、NaF+ThF_4+UF_4和NaCl+ThCl_3+UCl_3),采用基于反应堆安全分析和设计的综合性模拟程序SCALE(Standardized Computer Analyses for Licensing Evaluation),计算了中子能谱、反应性温度系数,分析了增殖比BR(breeding ratio)受反应堆裂变区、增殖区和ZrC中子反射层的尺寸影响、熔盐中~6Li和~(35)Cl同位素丰度的影响,以及熔盐密度误差对BR计算值的准确性影响、易裂变核素随反应堆运行时间演化等。在钍铀燃料循环熔盐快堆中,通过优化处理得到三种熔盐燃料方案的增殖比BR约为1.2。     

A phase-field simulation of uranium dendrite growth on the cathode in the electrorefining process

The uranium dendrite growth on the cathode during the pyroprocessing of uranium is investigated using a novel phase-field model, in which electrodeposition of uranium and zirconium from the molten-salt is taken into account. The threshold concentration of zirconium in the molten salt demarcating the dendritic and planar growth is then estimated as a function of the current density. Moreover, the growth process of both the dendritic and planar electrodeposits has been demonstrated by way of varying the mobility of the phase field, which consists of the effect of attachment kinetics and diffusion.     

NaCl-KCl熔盐体系电解制备金属铈工艺研究

为优化熔盐电解还原制备金属铈的工艺条件，开展了NaCl-KCl熔盐体系中CeCl₃的电化学行为及电解工艺研究。结果表明，在830 ℃下，以钼棒为工作电极、石墨棒为对电极、阴极电位高于1.9 V(Ag/AgCl为参比电极，下同)时，Ce³⁺可快速电解，提高Ce3+浓度有利于反应的进行。槽电压为4.41 V、相应的阴极电位为2.27 V时，电流效率最佳。固定阳极面积改变阴极面积的研究结果显示，随着阴极面积的减小，槽电压逐渐升高。实验条件下，槽电压随电极中心距的变化是线性的，与电极中心距的改变相比，电流的变化对槽电压的影响更显著。     

Electrolytic Extraction of Ce from NaCl-KCl Molten Salt

In order to optimize the technological conditions of cerium preparation by electrolytic reduction of molten salt, the electrochemical behavior of CeCl₃ in NaCl-KCl molten salt and the electrodeposition process on Mo electrode were carried out. The results indicate that Ce³⁺ can be quickly electrolyzed at the cathode potential more than 1.9 V (vs. Ag/AgCl) using Mo rod (ø4 mm). Increasing the concentration of Ce³⁺ is beneficial to the electrolytic reaction. The optimal electrolytic voltage is determined to be 4.41 V using two-electrode system, and the cathode potential is 2.27 V (vs. Ag/AgCl). It is found that the voltage increases with the decrease of cathode area when the anode area is fixed, and the cathode area is changed. Under the experimental conditions, the voltage varies linearly with the electrode center distance. Compared with the change of electrode center distance, the effect of current change on voltage is more significant.     

离子液体中电沉积锕系元素的研究现状北大核心CSCD

在核燃料的干法后处理中,高温熔融盐具有腐蚀性强、能耗大等缺点,而离子液体作为一种低温熔融有机盐,具有熔点低、离子电导率高、电化学窗口宽等优点,被用于回收核燃料中的锕系元素。介绍了离子液体组成、分类及特点,综述了锕系元素(钍、铀、镎、钚、镅)在第一代和第二代离子液体中的电化学行为,总结了离子液体中电沉积锕系元素存在的问题,并展望了该领域重点研究方向。     

(JAERI) Fourth International Symposium on Advanced Nuclear Energy Research

To increase the uranium recovery rate of molten salt electrorefining step in pyrometallurgical reprocessing of metallic fast reactor fuels, tests were carried out using electrorefiners equipped with mechanisms for scraping cathode deposits. After the modifications in the design of the anode basket and scraper mechanism, no stalling of the anode and scraper rotation due to interference by cathode deposits occurred. Under the condition that codissolution of zirconium and uranium was allowed in order to obtain maximum throughput, a current of 400–450A was maintained until 82% of the initially loaded uranium was recovered. The uranium recovery rate for the same duration reached 789 g U/h (32.9 g U/h_L per electrode volume). On the assumption that an electrorefiner operates for 20 h/d and 200 d/y in an actual pyrometallugical reprocessing facility, this result corresponds to a uranium recovery rate of 3.16 t U/y using only one electrode assembly of about 30 cm diameter, which should be a sufficiently high performance for practical use. From these results, the engineering feasibility of uranium recovery using an electrorefiner with cathode deposit scraper mechanism has been demonstrated.     

用放射性示踪法研究分离铀和铅、铋

用放射性示踪法研究了TBP－苯体系对铀和铅、铋的萃取分离。实验结果表明,在6mol/LHNO3介质中用TBP－苯作为萃取剂可使铀和铅、铋达到定量分离。阴离子交换法对铀进一步纯化后,利用分子电镀法制得厚度为500μg/cm^2的^233U同位素靶。     

Polarization Effects in the Molten Salt Electrorefining of Spent Nuclear Fuel

The effects of polarization in the electrorefining of spent nuclear fuel were analytically studied through electrotransport experiments with uranium. When the uranium concentration in molten salt was set at 0.5 wt%, polarization caused the measured cell resistance to increase from 0.16 to 0.33 Ω as the cell voltage was raised from 0.1 to 0.7 V. At 2.0 wt% uranium concentration in salt, on the other hand, the resistance was almost independent of cell voltage. A code named DEVON has been developed to estimate the effects of polarization on the electro- refiner operating condition. The Laplace equation is solved in the bulk salt region by finite element method. In the calculation, the effects of polarization are taken into account by adopting the diffusion layer model on defining the boundary conditions. The result of calculations agreed well with the measured resistance data at two sample concentrations for a diffusion layer thickness of 0.025 cm on the solid cathode. The calculations indicated that significant polarization at the cathode could be avoided by maintaining the uranium concentration in salt above 1 to 2 wt%. When it was held at 5 wt%, which is a typical level for normal operation, polarization proved to exert little influence on the cell resistance, but it was indicated to contribute appreciably toward flattering the current distribution along the cathode surface.     

Simulation of molten metal freezing behavior on to a structure

In the severe accident analysis of liquid metal reactors (LMRs), understanding the freezing behavior of molten metal onto the core structure during the core disruptive accidents (CDAs) is of importance for the design of next-generation reactor. CDA can occur only under hypothetical conditions where a serious power-to-cooling mismatch is postulated. Material distribution and relocation of molten metal are the key study areas during CDA. In order to model the freezing behavior of molten metal of the postulated disrupted core in a CDA of an LMR and provide data for the verification of the safety analysis code, SIMMER-III, a series of fundamental experiments was performed to simulate the freezing behavior of molten metal during penetrating onto a metal structure. The numerical simulation was performed by SIMMER-III with a mixed freezing model, which represents both bulk freezing and crust formation. The comparison between SIMMER-III simulation and its corresponding experiment indicates that SIMMER-III can reproduce the freezing behavior observed on different structure materials and under various cooling conditions. SIMMER-III also shows encouraging agreement with experimental results of melt penetration on structures and particle formation.     

Studies on applications of room temperature ionic liquids

Room temperature ionic liquids (RTILs) have many potential applications in nuclear fuel cycle, especially actinide and fission product separations. This paper outlines the results of work in our Centre directed towards identifying specific applications with respect to recovery of uranium and palladium from nitric acid media. The use of RTILs as diluents for extraction processes as well as electrolysis media have been explored. The extraction of uranium(VI) and palladium(II) from nitric acid medium by tri-n-butyl phosphate solution in RTIL has been studied. Voltammetric investigations on the suitability of RTIL as electrolytic medium for the electrodeposition of uranium and palladium at near ambient conditions are reported. The feasibility of electrodeposition of uranium as uranium oxide (UO₂) and palladium(II) as metallic palladium from the loaded organic phase has been demonstrated.     

基于OpenFOAM的熔融池自然对流传热与凝固数值研究

熔融物堆内滞留是第3代核电技术重要的严重事故缓解措施之一,堆芯熔融池在压力容器下封头壁面的热流密度分布直接影响该策略的有效性。本文基于开源的数值计算流体力学软件平台OpenFOAM,应用相变模型和浮升力模型二次开发了用于模拟堆芯熔融物由内热源或温差驱动的自然对流传热与相变求解器。应用该求解器模拟了瑞典皇家理工学院开展的二维氧化池与金属层耦合传热试验,获得了氧化池和金属层硬壳的相场,以及熔融池内的温度分布及沿容器壁面的热流密度分布。计算结果表明,该模型可用于熔融物凝固与自然对流的模拟,为深入分析核电厂采用熔融物堆内滞留措施后熔融池的行为奠定了基础。