碳基吸附剂对氢同位素的吸附行为研究(Ⅰ)

采用静态压差法研究了液氮温度下碳基吸附剂活性炭（AC）、碳分子筛（601）和碳纳米纤维（CNF）对氢同位素的吸附行为。实验结果表明：601对氢同位素的吸附量为最高，AC次之，CNF最小，并存在明显的同位素效应；吸附量的大小与吸附剂表面活性基团的数量有关；用浓HNO3对碳基吸附剂进行改性处理，在吸附剂表面引入氧杂原子，可增大这类吸附剂对氢同位素的吸附量。     

碳基吸附剂以氢同位素的吸附行为研究（Ⅱ）

研究了液氮温度下活性炭（AC）、碳分子筛（601）和碳纳米纤维（CNF）对H2、D2的吸附等温线，采用2种Langmuir模型对它们吸附H2、D2的等温线进行了理论计算。研究结果表明：在液氮温度下，3种碳基吸附剂对氢同位素的吸附等温线遵从Langmuir单分子层吸附模型，符合按活性点分类的定点吸附机制；吸附等温线可用Langmuir多项式理论模型进行准确计算。     

碳基吸附剂对氢同位素的吸附行为研究(Ⅱ)

研究了液氮温度下活性炭(AC)、碳分子筛(601)和碳纳米纤维(CNF)对H2、D2的吸附等温线,采用2种Langmuir模型对它们吸附H2、D2的等温线进行了理论计算.研究结果表明:在液氮温度下,3种碳基吸附剂对氢同位素的吸附等温线遵从Langmuir 单分子层吸附模型,符合按活性点分类的定点吸附机制;吸附等温线可用Langmuir 多项式理论模型进行准确计算.     

氙在活性炭和碳分子筛上的动态吸附性能

为筛选氙的吸附剂,研究了氙在活性炭和碳分子筛(CMS)上的动态吸附性能,探讨了氙浓度、气流比速、温度、载气、压力和CO2等对氙动态吸附系数的影响。结果表明,CMS1对氙的吸附能力最强,其次为CMS2;低于10-5mol/L的氙浓度、实验气流比速以及5×10-5mol/L以下的CO2浓度对氙动态吸附系数影响不明显;载气种类和高于5×10-5mol/L的CO2浓度对氙的动态吸附系数有一定影响;吸附温度和吸附压力对氙动态吸附系数影响较大。提高吸附剂吸附氙能力的方法主要是降低吸附温度和增加吸附压力。     

提高活性炭吸氡效率的液氮改性方法

优质椰壳活性炭被广泛用作氡、碘等气载放射性的吸附材料。为提高其吸氡能力,本文采用液氮浸泡、液氮浸泡与蒸发并行和低温氮气冲洗的活性炭改性方法,分别对优质椰壳活性炭进行了改性研究,并改进了静态法测量材料对氡的吸附系数的计算方法。结果表明,连续液氮浸泡与蒸发对活性炭改性的效果最好,改性活性炭对氡的吸附系数随连续液氮浸泡与蒸发次数的增加呈先增大后减小的规律,连续改性4次的改性效果最佳,改性活性炭的吸附系数提高了36%;液氮浸泡对活性炭改性也有一定效果,改性活性炭对氡的吸附系数最大可提高15%;低温氮气冲洗对活性炭改性没有效果。活性炭改性前后样品的BET表征结果表明,改性活性炭对氡的吸附能力的提高与054 nm孔径的微孔比表面积增加有明显的正相关性。该方法具有改性工艺简单、周期短、成本较低等优点。     

氙的超低温动态吸附特性

变温吸附是氙富集的重要手段，温度是影响氙吸附能力的重要因素。设计了超低温动态吸附实验平台，基于该实验平台研究了在-110～-60℃范围内碳分子筛对氙的吸附性能，并分析了-110℃下氙体积分数、气体流速、柱前压和柱内径对氙吸附性能的影响。结果表明，在-110℃下，氙体积分数和气体流速对氙的动态吸附系数影响最显著，柱前压和柱内径在一定范围内对吸附剂性能影响不大。     

几种多孔材料分析优选及其吸附氙的条件研究

在发生裂变反应的核设施中会产生放射性稀有气体氙(Xe)等。为保证反应堆的正常运行,须经过净化处理去除Xe等后才能排放,因此需滞留收集Xe等放射性气体。本文针对市售的5种多孔材料,包括颗粒状活性炭、分子筛和活性炭纤维3类,以材料的比表面积、孔容积为指标,结合Xe静态吸附容量,优选出性能较优的Xe吸附剂。研究了进气压力和吸附柱长径比对活性炭吸附Xe的影响,结果显示,活性炭吸附柱长径比为17∶1时,吸附性能最好。     

有机改性蛭石吸附U(Ⅵ)的行为及机理研究

通过静态吸附实验，研究了用十六烷基三甲基溴化铵（HDTMA•Br）改性的蛭石对U(Ⅵ)的吸附行为，以及有机改性蛭石（吸附剂）用量、pH值、铀初始质量浓度、吸附时间等因素对有机改性蛭石吸附U(Ⅵ)效果的影响，从热力学和动力学方面对吸附过程进行了分析，并通过FT-IR和SEM探讨了其相关吸附机理。结果表明：增加吸附剂用量、延长吸附时间和降低铀初始质量浓度都能提高有机改性蛭石对铀的去除率，最佳吸附pH值为6.5左右，120 min达到吸附平衡；用絮凝剂协同吸附能提高有机改性蛭石对铀的吸附效果；有机改性蛭石对铀的吸附遵循Langmuir吸附等温线，符合准二级动力学方程。有机改性蛭石吸附铀前后的FT-IR表明，-OH、Si[CDS1]O等基团起重要作用；SEM分析表明，有机改性蛭石吸附U(Ⅵ)引起其形态结构的改变。     

基于仿生多巴胺化学制备铀的吸附材料

铀的高效富集和分离对于核能可持续发展具有重要意义。吸附法作为一类重要的分离方法，吸附材料在其中扮演着关键角色。本文综述了近年来基于仿生多巴胺化学制备铀吸附材料的研究进展。第一部分首先介绍多巴胺化学的基本原理，着重讨论多巴胺的自聚合机理、聚集体结构及其聚合过程的控制因素；第二部分列举利用多巴胺化学表面改性制备不同类型的复合吸附材料，包括碳基纳米材料、多孔硅基材料、无机黏土矿物、金属或共价有机框架化合物、纳米高分子纤维等，探讨针对不同材料体系的多巴胺改性方法，以及对吸附材料组成、结构的影响；第三部分集中介绍多巴胺改性材料对铀的吸附性能研究，按照材料功能基团的差异，分为本征多巴胺涂层、多巴胺-无机复合涂层、多巴胺-高分子复合涂层三个方面，阐述各类材料对铀的吸附行为和机理。本文最后总结了多巴胺化学在吸附材料制备方面尚存在的挑战，并展望了本领域的发展前景。     

磁性富羧基碳复合材料的制备及对Pb(Ⅱ)、Ni(Ⅱ)、Hg(Ⅱ)和U(Ⅵ)的吸附

采用溶剂热法制备了富羧基碳,随后通过化学共沉淀法合成了磁性富羧基碳复合材料。利用透射电子显微镜(TEM)、红外光谱分析(FTIR)、X射线衍射(XRD)、振动样品磁强计(VSM)、热重差热分析(TGA)、zeta电位分析及比表面积(BET)等手段对磁性富羧基碳的形貌、组成、结构、磁性以及表面电荷特性等进行了表征,并考察了富羧基碳和磁性富羧基碳对Pb(Ⅱ)、Ni(Ⅱ)、Hg(Ⅱ)和U(Ⅵ)的吸附性能。结果表明:富羧基碳经磁性改性后表面负载了铁氧化物纳米颗粒,比表面积由29.2m2/g提高到45.4m2/g,热稳定性提高,由磁滞回线可知,磁性富羧基碳的饱和磁化强度为30.68A.m2/kg。Pb(Ⅱ)、Ni(Ⅱ)、Hg(Ⅱ)和U(Ⅵ)在磁性富羧基碳上的平衡吸附容量分别为477.50、23.50、260.20、54.86mg/g,低于富羧基碳,吸附等温线符合Langmuir等温模型。从磁性富羧基碳对Pb(Ⅱ)、Ni(Ⅱ)、Hg(Ⅱ)和U(Ⅵ)均具有较高的吸附容量和不同吸附剂对U(Ⅵ)吸附容量的比较可以看出,该吸附剂是重金属污水和放射性废液处理领域中极具发展前景的吸附材料。     

基于双塔式氢氦/氚氦混合气的快速分离技术

氢氦/氚氦混合气快速高效地分离与回收是产氚工艺的关键技术之一。利用液氮温度下吸附剂对氢同位素与氦吸附能力的差异,搭建了双塔式固定床低温吸附-解吸分离氢氦/氚氦的实验装置,通过该实验装置开展了不同组成的氢氦、氚氦混合气的分离实验。实验结果表明:采用双塔式固定床低温吸附-解吸法可以实现不同组成的氢氦、氚氦混合气的快速分离,分离后氦中氢的体积分数低于1.2×10-5,氦的纯度可达到99.998 8%,吸附柱的脱氚率大于97%;双塔式固定床低温吸附-解吸法的解吸氢中含有较高浓度的氦,不适于回收氢;在氚氦分离中采用固定床低温吸附柱是可行的,可作为钯膜分离器的辅助单元。     

Calculation of Breakthrough Curve of Multicomponent Hydrogen Isotopes Using Cryosorption Column

The effective tritium system should be designed to recover tritium from DT reactor blanket sweep gas in a form that is easy to transfer to the main fuel cycle. The cryosorption method using a porous adsorbent at the temperature of liquid nitrogen is one of the candidate processes for extracting tritium from the sweep gas. For designing of a cryosorption column for recovery of tritium from hydrogen-swamped helium sweep gas, it is necessary to predict the breakthrough curve for mixture of multicomponent hydrogen isotopes in helium. In this report, a method to calculate the breakthrough curve at cryosorption of multicomponent hydrogen isotopes on molecular sieve 5A, molecular sieve 4A or activated carbon at 77.4 K is presented.     

Adsorption Isotherms of Hydrogen Isotopes on Molecular Sieves 5A at Low Temperature

Cryogenic Molecular Sieve Bed (CMSB) is considered to be applied to the bred tritium recovery system or the helium glow discharge exhaust gas cleanup system of nuclear fusion reactor. Molecular Sieves 5A (MS5A) is one of the most possible candidate adsorbents for CMSB. To design the CMSB, adsorption isotherm of hydrogen isotopes for MS5A must be investigated in liquid nitrogen temperature region (around 77 K) and above, and isotherm equation which can express the experimental data obtained in wide pressure range with good accuracy needs to obtaining. The present authors carried out the experiments using the volumetric method to obtain the adsorption isotherm of H₂ and D₂ for MS5A. Adsorption isotherms were obtained in the pressure range between about lPa and 0.2MPa at 77K (liquid nitrogen), 87K (liquid argon), 113K (isopentane), 143 K (n-pentane), 155 K (ethanol) and 195 K (dry ice/ethanol). Two Sites Langmuir Model was applied to understand adsorption isotherms, and was able to express the experimental observation with fairly good accuracy. The apparent heats of adsorption for two kinds of activated adsorption sites were obtained from temperature dependence of adsorption isotherms. Furthermore, parameters of adsorption isotherms for residual 4 hydrogen isotopes (HD, HT, DT and T2) were estimated using reduced mass.     

Experimental study on the adsorption and desorption of tritium in the graphite materials for HTR-PM

Tritium behavior in the reactor such as production, diffusion and release are accompanied by their adsorption and desorption in graphite materials, which are essential to the safety of high temperature gas cooled reactor (HTGR). In order to study this important issue, hydrogen instead of tritium is experimentally used in this work and justified viable by theory. By performing multiple sets of comparative experiments, the features of hydrogen adsorption and desorption behavior changing by adsorption temperature and time in typical graphites used in HTR-PM (High Temperature Gas Cooled Reactor – Pebble Bed Module), i.e. reflective layer, fuel element and boron carbon bricks, have been observed and analyzed. Furthermore, the adsorption rates of hydrogen in the three materials as above at different conditions are also given. Based on the experimental results, tritium behavior in the HTR-PM was inferred and estimated, which is significant for the further study on the mechanism of tritium transport.     

Permeation Analysis of Tritium Through the Vessel Wall of a Titanium Hydride Storage Container

Abstract

A preliminary design for a stainless steel vessel for the long-term storage of hydrogen isotopes has been proposed. The immobilised hydrogen, as a titanium hydride, could be stored in a stainless steel vessel for this application. The vessel, as a primary package, is designed to form titanium hydride and to contain the hydrogen isotopes and helium-3 produced from the decay of tritium. In order to predict the possibility of contamination and the deterioration of the mechanical properties, a numerical diffusion analysis calculation of the hydrogen isotopes and helium inside the stainless steel vessel was carried out. Numerical results showed that a negligible amount of tritium would be released by permeation through a 0.7 cm thick vessel wall at normal conditions over the entire period of the storage. When the vessel is heated up to a temperature of 600^°C for the routine conditions of activation or exothermic hydriding, tritium loss or contamination would be of little concern. However, if the vessel were exposed to fire conditions with a temperature of 800^°C, permeation of hydrogen through the vessel wall would result in a serious increase in the amount of tritium escaping, in a very short time.     

贮氢材料在氚技术中的应用

简要介绍了在氚技术中应用贮氢材料的意义和在氚技术中应用的贮氢材料的研究现状、典型贮氢材料的特性、贮氢材料用于氚技术的优点，及贮氢材料在工业规模的氚处理技术中的应用情况。     

无机吸附材料处理放射性废水中铀的研究进展

核能与核工业的发展不可避免地会产生大量的含铀放射性废水。随着材料科学的发展,新型吸附材料不断出现,吸附法处理放射性废水近年来得到了特别关注。目前研究的无机吸附材料可分为无机矿物、金属氧化物、碳基材料等。通过接枝、交联、等离子体、复合等技术处理,在吸附材料表面修饰含氧官能团或含氮官能团,可提高对铀的吸附性能和选择性。铀的吸附机理多表现为离子交换和表面络合作用。本文主要介绍了无机吸附材料处理放射性废水中铀的研究进展,并对今后的研究方向提出了建议。     

中国HCCB-TBM氚增殖单元三维多物理场耦合氚输运模拟分析

中国氦冷固态实验包层模块（HCCB-TBM）将在国际热核聚变实验堆（ITER）上安装测试,以验证其氚增殖能力与核热移出能力。HCCB-TBM中的氚输运与流体的传热和传质、氢同位素交换、结构材料的SORET效应密切相关。考虑以上物理因素,基于商业软件COMSOL完成了HCCB-TBM氚增殖单元多物理场耦合的氢同位素输运模拟分析。分析结果表明：球床吹洗气体中含氢有助于抑制氚渗透损失;当吹洗气体含氢浓度为4.66×10^-2 mol/m³时,产生约13.2倍的氚渗透阻止效应。     

Optimization for the tritium isotope separation factor and permeation by selecting temperature and thickness of the diffusion Pd-Ag alloy cathode

Large quantities of tritiated water will be produced in the controlled fusion reactors for power generation. To eliminate the concentrated tritiated water and for recycling tritium, an industrial electrolyzer was developed. The aim of this paper is to give the design of this electrolyzer and the results for optimization in diffusion and in isotopic exchange by selecting thickness of a thimble-shaped Pd-25%Ag cathode working at high temperature and current. In this process, the tritium recovery system is based on the principle of the tritium diffusion Pd-Ag cathode which produces very pure hydrogen isotopes from enriched tritiated water.     

Numerical Estimation Method of the Hydrogen Isotope Inventory in the Hydrogen Isotope Separation System for Fusion Reactor

In the fuel cycle system of the ITER, a large fraction of tritium inventory is expected to be in the cryogenic distillation columns of the hydrogen isotope separation system (ISS). Therefore, the numerical estimation method of hydrogen isotopes inventory in the ISS with high precision is strongly required from safety point of view. Two series of experiments were performed to establish the numerical estimation method of the overall hydrogen isotope inventory in the ISS at steady state using ITER-scale large cryogenic distillation columns at the Tritium Systems Test Assembly in the Los Alamos National Laboratory under the US-Japan collaboration on tritium safety engineering. As a result of experiments, it was confirmed that the hydrogen isotope inventory in a cryogenic distillation column was estimated by the numerical estimation method proposed in this work with enough high precision from the engineering point of view, and it was proved that this method was applied for the ITER-scale cryogenic distillation columns. The precision of this estimation method was found to be almost independent on the composition profile in columns, and especially the liquid holdup ratio of deuterium to the volume of the column was less influential in the inner diameter of the packed section. In addition, the gaseous inventory in an ITER-scale cryogenic distillation column was found to have considerable impact on the total amount of holdup of the column.