冠状化合物在锂同位素分离中的应用

锂有两种稳定的同位素且在核能工业中都有重要的应用,工业上分离锂同位素的方法为锂汞齐法,但该法需使用大量有毒的汞,对人类健康和环境卫生带来了严重问题,因此寻找一种绿色有效的替代方法势在必行。自冠醚和穴醚合成后,在锂同位素分离上的优良特性使其成为了国内外研究热点,本工作将近40年来冠状化合物在锂同位素分离中的研究成果进行了系统的归类和总结,为该领域的进一步研究提供参考。     

Uranium Isotope Separation by Cation Exchange Chromatography Using Uranous Sulfate Complexes

A nearly ideal displacement chromatography has been realized with an eluent of MgS0₄ and H₂SO₄ in the study of uranium isotope separation by means of cation exchange chromatography using uranous sulfate complexes. Uranium-235 was enriched at the end of the chromatogram and ²³⁸U was enriched at the front. Two long distance displacement experiments have been carried out, keeping an isotopic plateau region on the chromatogram. Consequently, good accumulation of the isotopic fractionation based on uranous-sulfate complex formation reactions obtained. The separation coefficient ε of this system was estimated to be about 5×10^?5.     

离心萃取级联分离锂同位素的数学模型

萃取法分离锂同位素有望替代汞齐法消除汞害,但需多级萃取才能获得高丰度同位素,采用离心萃取机替代萃取澄清槽形成萃取级联系统可提升分离效率。基于萃取法分离锂同位素、离心萃取分离原理和级联理论,借鉴气体离心级联分离同位素的方法,引入分流比概念,建立了离心萃取级联分离锂同位素单级、多级的数学模型和级联的平衡时间模型,对离心萃取级联分离锂同位素进行计算分析。离心萃取级联是一种类似全回流矩形级联形式,取料量对级联级数有着很大的影响,级联存在最大取料丰度限制,级联平衡时间受到目标丰度和离心萃取机级停留时间(处理能力)影响,采用多步法级联可有效减少平衡时间。该数学模型可指导工艺的设计,为下一步的产业化应用提供理论依据。     

ABSTRACTS OF 1993 AESJ AWARDS

The UB3LYP/LanL2DZ level calculations were carried out for sixty-seven Li-M diatomic molecules of lithium between LiH and LiBi to explore the periodic properties of their ⁶Li-to-⁷Li isotopic reduced partition function ratios (rpfrs) and some other quantities. The Li-M bond distance, the frequency shift upon ⁷Li/⁶Li isotope substitution and the rpfr all show plots typical of any chemical and physical property which is a periodic function of the atomic number. The rpfr is strongly correlated with the Li-M bond stretching force constant except for LiH. The present calculations show that the rpfrs of diatomic molecules of group 2, group 12 and group 18 elements are relatively small, which reflects the filled electron shell and subshell characters of those elements. The results of the calculations and the consideration on chemical properties of elements suggest that zinc is a possible substitute for mercury in lithium isotope separation processes utilizing the redox reaction of lithium.     

自动电位滴定硼浓度方法在MOFs对硼同位素分离效果测定中的应用

金属 有机骨架（MOFs）材料作为吸附剂具有吸附硼同位素的潜力,为系统研究硼同位素效应,本文建立测定硼酸溶液中硼浓度的自动电位滴定法,以三种MOFs为例测定其对硼同位素的分离效果。采用弱酸强化法,甘露醇用量为理论用量的4倍,硼酸标准物质的测量值与参考值之差最小（-0.000 13 g）,方法的测量不确定度为0.000 2~0.000 8,测量精度为0.10%~0.40%,方法有效、可靠。应用建立的自动电位滴定法测定吸附前、后硼酸溶液的硼浓度,用MC-ICP-MS测定吸附前、后硼酸溶液的硼同位素丰度比¹⁰B/¹¹B,以Cu-MOF-OCH₃、UiO-66-NH₂、MIL-101(Cr)-2,3-OH三种MOFs材料为例,测定其对硼同位素的静态分离效果。结果表明,Cu-MOF-OCH₃、UiO-66-NH₂和MIL-101(Cr)-2,3-OH对硼同位素的分离因子(S)分别为1.066、1.037和1.079,均大于商用树脂Amberlite IR743的S（1.027）,其中,Cu-MOF-OCH₃对¹⁰B的10/11S>1,UiO-66-NH₂、MIL-101(Cr)-2,3-OH对¹¹B的^11/10S>1。本结果可为系统研究MOFs材料对硼同位素的分离效果提供参考。     

Isotope Separation with Drift Tube, (I)

A new method of isotope detection and separation based on transport phenomena of ions in gases, which consist of a drift tube, is proposed and the analytical expression of resolution power of the method has been derived from a diffusion equation. The expression shows that the resolution power increases with the square root of the voltage supplied to the tube. A simple drift tube was constructed and natural Li was isotopically separated in Ne 100 Torr with the maximum resolution power, about 2. The variations of the resolution power with the applied voltage were measured by using the ion source of ⁶Li and ⁷Li separately and compared with calculations.     

Determination of Li-6/Li-7 Isotopic Ratio by Means of Thermogravimetric Analysis for Lithium Sulphate Monohydrate

Plutonium concentrations and burnup at Pu spots were calculated in U-Pu mixed oxide (MOX) fuel pellets for light water reactors with the neutron transport and burnup calculation code VIMBURN. The calculation models were suggested for Pu spots and U matrices in a heterogeneous MOX fuel pellet. The calculated Pu concentrations and burnup at Pu spots were compared with the PIEs data in a MOX pellet (38.8 MWd/kgHM). The calculated Pu concentrations agreed by 5–18% with the measured ones, and the calculated burnup did by less than 10% with the estimated one with the measured Nd concentrations. Commercial PWR types of MOX fuels were also analyzed with the calculation code and the models. Burnup at Pu spot increased as the distance was greater from the radial center of a MOX fuel pellet. Burnup at Pu spots in the peripheral region became 3–5 times higher than pellet average burnup of 40 MWd/kgHM. The diameters (20–100 μm) of Pu spots were not found a significant factor for burnup at Pu spots. In the outer half volume region (outer than r/r _o=0.7) of a MOX fuel pellet, burnup at Pu spots exceeded 70MWd/kgHM (the threshold burnup of microstructure change in UO₂ fuel pellet) at pellet average burnup of 1430 MWd/kgHM.     

Zinc Isotope Fractionation on Benzo-15-crown-5 Resin by Liquid Chromatography

Chromatographic fractionation of zinc isotopes was performed on the synthesized benzo-15-crown-5 resin as a column packing material at 323K in the breakthrough manner for both a frontal and a rear bands. Zinc adsorption capacity was affected by anion chloride concentration and solvent dielectric constant. The heavier zinc isotopes were found enriched to the solution phase and the lighter zinc isotope was concentrated on the resin phase. The frontal maximum enrichment ratio for isotopic pair of ⁶⁸Zn/⁶⁴Zn was 1.0081. The isotope separation coefficients for isotopic pair of ⁶⁸Zn/⁶⁴Zn for frontal and rear band, were 5.3 × 10^?4, 4.5 × 10^?4, respectively.     

氢-水同位素交换反应热力学理论研究

本文采用量子化学从头计算法对氢同位素分子及相应的氢同位素水分子进行了几何结构优化和振动频率计算,得到了6种氢-水同位素交换体系的热力学函数和气相反应平衡常数。研究结果表明:平衡常数的理论计算值与实验结果吻合,在0.1 MPa和283.2~373.2K的反应条件下,HD-H2O体系平衡常数的计算值与实验值间相对偏差小于6%。     

An Apparatus for Isotopic Ratio Measurement in UF5 Formed by Infrared Multiphoton Dissociation of UF6 in Molecular Beam

A Separation factor was measured in isotopically selective infrared multiphoton dissociation (IRMPD) of supercooled UF₆ in a supersonic expansion by multiphoton ionization (MPI) and time-of-flight mass spectrometry (TOFMS). A pulsed free-jet nozzle was used to generate a UF₆-molecular beam seeded in Ar (–10^?7 Torr in UF₆ partial pressure). Two-frequency ρ-H₂ Raman laser beams around 16μm were used for the dissociation of UF₆ under collisionless conditions in the molecular beam where the flow velocity for UF₆ is about 500m/s. The ²³⁵U/²³⁸U isotopic ratios in nascent UF₅ photoproducts were determined by selective MPI of UF₅ at 532 nm followed by TOFMS with a mass resolution as high as 1200. A separation factor of about 2 was observed under the experimental conditions chosen for the demonstration of this method.     

Isotope Effect and Isotope Separation: A Chemist's View

The behavior of uranyl fluoride complexes containing different isotopic species [¹⁶O-U-¹⁶O]²⁺, [¹⁶O-U-¹⁸O]²⁺, [¹⁸O-U-¹⁸O]²⁺ in isopropanol solutions under UV irradiation was studied. The rate of decrease in concentration of uranyl complexes containing isotopic species [¹⁶O-U-¹⁸O]²⁺ is higher than that for uranyl containing [¹⁸O-U- ¹⁸O]²⁺ species. It was shown that this phenomenon is not caused by difference in extinction energy of vaious isotopic species.     

Mass Transfer Model of Purex Process in Mixer-Settlers

The formation rate of ruthenium tetroxide (RuO₄) from nitrosyl ruthenium trinitrate (RuNO(NO₃)₃) was measured at temperatures of 70–115°C in 3–9 mol·dm^?3 nitric acid solutions. The gas-liquid equilibrium ratio was measured at temperatures of 40–80°C in 0.1–9 mol·dm^?3 nitric acid solutions. The gas-liquid equilibrium ratio of RuO₄ ranged about 60–260 under the experimental conditions. The reaction rate increased greatly with acid concentrations above 6 mol·dm^?3. The activation energy of the reaction was about 130 kJ·mol^?1 in 9 mol·dm^?3 nitric acid solution. It was concluded that the rate of RuO₄ formation dominated the distill-out phenomena of Ru in an evaporator as used in nuclear fuel reprocessing plants.     

氢-水同位素交换及其应用研究进展

简要介绍了氢气与水之间的氢同位素交换(氢—水同位素交换)的原理和相关理论研究,重点阐述了几种主要氢—水同位素交换工艺的研究和应用进展,并对氢—水同位素交换工艺在氢同位素分离中的应用前景进行了评述。     

Determination of the separation factor of lithium isotopes in ion exchange

The isotopic equilibrium between the solutions of lithium salts (LiOH and LiCl) and SBS, KU-2, and Dowex-50 cationites is investigated. It is shown that, in the first place, the Li⁷ isotope was concentrated in the solution in all the cases which were investigated; in the second place, there is a dependence of the separation factor value on the nature of the cationite; in the third place, in 1 N to 5 N solutions of LiCl, the value of a does not depend on the concentration of the solution.In conclusion, we extend our sincere thanks to Professor G. K. Boreskov for his advice and continued interest in the work.     

Selectivity Loss Due to Magnetic Field in Laser Isotope Separation of Gadolinium Based on Polarization Selection Rules

The magnetic field effect on the isotopic selectivity with J=2→2→1→0 multistep photoionization was studied by the experiment and the numerical analysis. Three linearly polarized dye laser pulses were used to photoionize the atomic gadolinium and the isotopic selectivity was measured by changing the magnetic field strength and the angle between the laser polarization and the magnetic field. The experimental data was reproduced well by the numerical simulation. From the oscillatory behavior of the isotopic selectivity, the Lande factor of the high-lying excited level (34,586.7 cm^-1) of atomic gadolinium was determined.     

基于光化学锂同位素分离条件的同位素比率测量

从光化学锂同位素分离实验研究的需求出发,基于其分离条件,提出了一种测量锂同位素比率的方法。该方法利用锂原子蒸气对探测光吸收峰的峰值来计算锂的同位素比率,避开了测量原子密度时所需的吸收信号频率定标与光强随频率变化积分中积分限的选择问题。该方法还根据锂同位素吸收谱的特殊性采用具有较强吸收效应的⁶Li的D₂线对应的吸收峰峰值,可在原子蒸气中⁶Li含量较低时提高对比率的测量精度。设计并搭建了实验装置,对该方法进行了测试。同一条件下所测得的同位素比率相对标准偏差小于1%,表明该方法对光化学分离方法中锂同位素比率相对变化是敏感的。这意味着该方法可作为以原子蒸气为分离介质的激光锂同位素分离研究的诊断手段。     

Quantum Chemical Calculation of O-H Vibration in LiOH Ab-initio Analysis of Hydrogen Isotopes in Ceramic Breeder Materials

The stretching vibrational frequency of O-H in LiOH crystal was calculated using CRYSTAL98 code. Hartree-Fock (HF) and hybrid (B3LYP) methods were used. By taking account of reduced mass, O-D or O-T frequencies could be also estimated. The obtained O-D frequencies were 2,994 cm^-1 in HF level and 2,740 cm^-1 in B3LYP. Agreement with experimental data, 2,713 cm^-1 reported by Buchanan et al., was much better in B3LYP than in HF. The result of the present calculation supported the assignment in our previous FT-IR study, where O-D vibration in the Li₂O single crystal that was treated by thermal absorption of D₂ was observed. The peak observed at 2,715 cm^-1 was attributed to O-D in LiOD phase. The present study showed that the quantum chemical analysis combined with the FT-IR was a powerful tool to study the behavior of hydrogen isotopes in the ceramic breeder materials.     

Measurement of the isotopic abundance of boron-10 by inductively coupled plasma-quadrupole mass spectrometry

This article describes the method for measuring the isotopic abundance of ¹⁰B in nuclear grade boron carbide using inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS). The results of investigation revealed that both the integration time and the dwell time have a major influence on the reproducibility of ICP-QMS measurements. As a result of optimization of the measurement conditions, reproducibility below 0.2% relative standard deviation (RSD) (0.17% RSD maximum) was achieved. In addition, the measured value of the isotopic abundance of ¹⁰B for each sample well agreed with the values measured by the TIMS. Thus, the method described in the present investigation was very effective in the analysis of isotopic abundance of ¹⁰B in B₄C or H₃BO₃. The results of this study suggest that ICP-QMS could be applied to the precise analysis of the isotopic abundance of ¹⁰B required in the field of nuclear applications.     

Deuterium diffusion in LiOH–water-corroded oxide layer of zirconium alloys

In order to clarify the hydrogen diffusion mechanism in the oxide layer of zirconium alloys, in situ hydrogen isotope diffusion in the oxide layer has been examined. The zirconium alloys used were Zircaloy-2, GNF-Ziron (Zircaloy-2 type alloy with high iron content) and VB (zirconium-based alloy with high iron and chromium contents). They were corroded in 1 or 0.1 M LiOH-containing water at 563 K, producing oxide layers of 1.1–2.1 μm in thickness. The diffusion experiments were carried out in the temperature range from 488 to 633 K by using a combined technique of deuterium plasma exposure and nuclear reaction analysis for D (³He,p)⁴He reaction. From the transient deuterium profiles in the oxide layers, it was concluded the LiOH–water-corroded oxides had a single-layer structure, which was in contrast to the double-layer structure previously observed in steam-corroded oxide layers. The diffusion coefficients in the 1 M LiOH–water-corroded oxides evaluated from the deuterium profiles were smaller in the order of Zircaloy-2 > GNF-Ziron > VB at 573 K. For the 0.1 M LiOH–water-corroded oxide of GNF-Ziron, the diffusivity was lower than that of the 1 M LiOH–water-corroded oxide by a factor of 1/4. The present diffusion coefficients of the 1 M LiOH–water-corroded oxides of GNF-Ziron and VB were approximately 7 times larger than the previous data of the corresponding steam-corroded oxides. The deuterium diffusion properties in the oxides of the three alloys obtained in the in situ experiment were roughly consistent with their hydrogen absorption performances in the LiOH–water-corrosion tests, as well as in the previous steam corrosion tests.     

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。