~5H-川芎1号碱的标记中金属催化剂催化氢-氚同位素交换反应的研究

制备高比度氚标记化合物的方法主要有催化加氚法,催化卤-氚交换法和催化氢-氚同位素交换法。催化剂本身并不参加化学反应,只在其表面吸附氚气从气相进入液相或固相,改变反应速度,提高标记物的比度。常用的催化剂有钯、铂、铑等过渡金属元素。李志敏的工作证明钯-碳催化剂在催化加氚反应中不仅有催化作用,而且对氢-氚体系而言,还有明显的分离作用。     

U(Ⅲ)-U(Ⅳ)同位素交换过程的同位素效应

本文研究了U(Ⅲ)-U(Ⅳ)在7.0mol/l HCl介质中及在U(Ⅲ)-7.0mol/l HCI-U(Ⅳ)-50％TBP-煤油和U(Ⅲ)-7.0mol/l HCl-U(Ⅳ)-50％TBP-二甲苯体系中的同位素交换过程,测得上述体系的单级分离因数分别为1.0026,1.0031和1.0030,从而证实了P.Delvalle的1.0025-1.0030的实验结果;确认了用液态Zn-Hg齐制备U(Ⅲ)是快速、有效的方法;初步探索了用U(Ⅲ)-U(Ⅳ)交换过程浓缩~(235)U的合适体系。     

化学交换反应法分离硼同位素的数学模型

采用化学交换反应法,针对三氟化硼-苯甲醚分离体系,研究了硼同位素分离生产过程的特点,建立了交换精馏塔的稳态数学模型,并利用Matlab程序进行模型求解,得到了不同分离要求和操作条件对交换精馏塔理论塔板数的影响.当增大所需同位素丰度或改变分离温度以及回流比时,都会使得理论塔板数增加或减少.该数学模型可以指导工艺设备的改进和优化,为下一步的放大和操作过程提供了理论依据.     

利用稳定同位素δ~(18)O估算湖泊渗漏量

基于稳定同位素质量平衡及水量平衡,推导了内陆湖泊稳定同位素模型,结合羊卓雍错氧同位素数据计算了羊卓雍错湖水渗漏量。讨论了湿度因子、温度因子对湖泊渗漏量的影响。结果表明,在其他影响因子不变条件下,渗漏量所占比重越大,湖水δ18O值越负。羊卓雍错湖每年的渗漏量达到补给量的30.6%。     

同分子同位素反应及催化剂应用

轻同位素的工业化富集主要采用精馏法,如H₂、O₂、N₂、CO等,这些双原子分子同位素气体在富集中后期,会受到其他同位素干扰而无法得到高丰度的同位素,需要在精馏级联中间增加反应转化装置,排除同位素干扰。在催化剂的作用下,气体分子之间发生反应,同位素原子得到重新组合生成单一同位素气体,继续分离得到高丰度的同位素气体。本文对同位素气体反应及采用的催化剂进行介绍,并着重介绍了C同位素交换反应的平衡常数、反应机理等特性。     

U(Ⅳ)-U(Ⅵ)同位素交换反应动力学研究 Ⅰ.Fe~(2+)对U(Ⅳ)-U(Ⅵ)同位素交换反应的催化作用

一、前言由于U(IV)-U(VI)同位素交换体系具有相当大的同位素效应和很好的稳定性,并且容易实现两相回流,这对于分离U同位素的工业应用都是十分有利的。但是,U(IV)-U(VI)同位素交换反应速度非常慢,常温下H~+浓度为1.0—4.0 mol/l时,速度常数为1.0×10~(-4)l~2/mol·s。因此要用U(IV)-U(VI)交换体系浓缩铀同位素,必须研究U(IV)-U(VI)交换反应动力学,找到加快交换反应的方法。     

~(12)C与~(209)Bi反应中Au同位素的产额与Q_(gg)的关系

用47MeV/u12C离子轰击天然铋靶,通过炮弹和靶核之间的核子转移反应产生Au同位素。使用放射化学方法从大量Bi和复杂反应产物中分离、纯化Au,并制备Au的γ射线测量源。使用HPGe探测器测量放射性Au同位素的γ活性。根据照射结束时Au同位素的活度和其他相关数据,确定每个Au同位素的产生截面。分析发现,缺中子Au同位素的产生截面与Qgg值之间不遵从指数依赖关系,这可用重离子碰撞中的次级过程加以解释。     

氢-水同位素催化交换速率及过程模拟的研究进展

氢-水同位素催化交换在处理ITER聚变堆废水以及核裂变反应堆重水升级方面具有应用前景。该交换过程及核心设备催化交换塔的模型化研究,对工艺和工程优化设计具有十分重要的意义。本文重点介绍了氢-水同位素催化交换过程模拟的研究进展,讨论了同位素催化交换速率的计算方式以及吸收塔模型和滴流床模型在同位素催化交换过程模拟中的应用,探讨了氢-水同位素催化交换过程模拟今后的研究方向。通过各类模型的比较,滴流床模型被认为在催化交换过程模拟中有良好应用前景。氢-水同位素催化交换机理及速率计算方法和催化交换塔模型化等方面有待进一步研究。     

~(147)Nd同位素稀释亚化学计量法测定聚乙炔中钕

钕是稀土催化剂法合成聚乙炔过程中所必需的成分,合成后,钕在聚乙炔中的剩余含量会影响聚合物的稳定性。本文介绍了用同位素稀释亚化学计量法测定聚乙炔中的钕,方法的灵敏度为0.05μg钕。     

Preliminary Experiments on Hydrogen Isotope Separation by Water-Hydrogen Chemical Exchange under Reduced Pressure

A pressure-reducing method is used effectively in a water distillation process to enhance the equilibrium separation factor. The feasibility of the technique is established through application to a water-hydrogen chemical exchange process using a prototype separation column. Isotope separation experiments examining the water-hydrogen chemical exchange reaction are performed for column pressures of 12–101 kPa, and the separation factors for hydrogen and deuterium are obtained. The HETP (Height Equivalent to a Theoretical Plate) values were distributed in the range of 6 to 15 cm. By reducing the pressure in the column, the process temperature can be lowered without reducing the molar fraction of water vapor in the gas stream. It confirmed that the separation factors under reduced pressure are larger than under atmospheric pressure. This fact demonstrates the effectiveness of reduced pressure in water-hydrogen chemical exchange processes.     

Theory of Chromatographic Separation of Isotopes

A fundamental equation for chromatography is derived starting from a very simple concept that the chromatographic movement of species can be expressed as the sum of the movement caused by the external force and the movement caused by the internal concentration gradient and its transformations into appropriate forms are discussed in the cases of ion exchange (or gas) chromatography and ionic migration, without or with a counterflow.

By solving the fundamental equation, making appropriate assumptions, a comprehensive expression which describes the concentration profile is derived for two-isotope systems in any kind of chromatography.     

高丰度硼同位素分离生产技术的研究进展

通过对硼同位素分离生产技术发展过程的分析,认为化学交换精馏法仍是目前能够实现工业化的主要方法,并提出了存在的问题及发展方向。     

离心法分离锗同位素实验研究

采用气体离心法,以GeF4作为分离介质,通过国产离心机的单机实验成功分离了锗同位素,初步掌握了不同供料流量、分流比下GeF4离心分离的基本全分离系数,得到的基本全分离系数大于1.40,并且通过1-2-1级联实验及相关计算,对高丰度76GeF4产品的生产进行了模拟。实验证明,以GeF4为工作介质,采用国产离心机分离锗同位素可以获得高丰度的76GeF4产品。     

Enrichment of the Uranium Isotopes by Electromigration in a Cation Exchange Membrane

The γ-radiolysis of water subjected to gas bubbling has been studied using a specially desinged gasloop. During the irradiation, N₂ gas was bubbled from the bottom of the irradiation vessel. As the N₂ gas feed rate was raised, the apparent G(H₂) value increased in keeping therewith, from 5 × l0^?3 to 0.26. However in the presence of a sufficient amount of O₂ or H₂O₂, G(H₂) was raised almost to the level of the molecular yield. With reasonable assumptions, it could be concluded that 3～5 × 10^?6 mol/l of H₂O₂ was sufficient to reduce the back reaction of molecular products to less than 10% under the present experimental conditions. It was also found that the G(H₂) value increased with CH₃OH concentration roughly in proportion to log(CH₃OH), and reached 3.1 with 0.1 mol/l CH₃OH.     

74Se同位素分离研究

针对分离装置对工作介质的特殊要求，选择SeF6作为分离工作介质，并进行了单机分离试验，获得适用于级联设计的单机参数和单位质量数差的全分离系数γ0。进一步研究中，借鉴其它稳定同位素分离经验，建立了直角级联模型，并开展了级联分离计算，通过理论计算，讨论了74Se同位素级联分离特性。上述研究表明，采用专用方法分离74Se同位素是可行的。     

矩分析在硼同位素分离色谱中的应用研究

以D301-G树脂为固定相,水为流动相,通过矩分析研究2种硼同位素在给定条件下的色谱特征,基于平衡-扩散模型、线性驱动力模型估算了硼酸在固定相上的动力学参数。研究结果表明,同位素10B在树脂相上的色谱保留时间大于11B;硼酸在D301-G树脂相中的轴向扩散系数和集总传质系数均随温度的升高而增大,室温下轴向扩散系数为1.08 cm2/min,集总传质系数为0.65 min-1。     

Nuclear Magnetic Resonance Study of Ligand Exchange Reaction in Lanthanum Nitrate Complex with n-Octyl(phenyl)-N,N-Diisohutylcarbamoylmethylphophine Oxide

The Molten Salt Reactor (MSR) concept has recently been considered as one of the candidates for the generation IV nuclear power systems. MSRs have many advantages such as improved safety, proliferation resistance, resource sustainability and waste reduction. But MSR developmental activities have lagged and there are few data available to support detailed analyses. However, the authors believe that additional investigations are merited for future study. From this point of view, the authors have analyzed the depressurization accident of the MSR “Fuji-12” using a newly developed MSR transient analysis code. In Fuji-12, a small amount of helium gas bubbles are circulated in the primary loop for stripping out gaseous fission products. A depressurization of the primary system would cause these bubbles to expand, resulting in a positive reactivity insertion. We have attempted to determine the severity of such an accident. Although the analysis is still preliminary and the assumptions are crude, it can be expected that the depressurization would not result in a severe accident in Fuji-12.