Gadolinium Isotope Separation by Cation Exchange Chromatography

Displacement chromatographies of Gd adsorption band in cation exchange resin were performed to observe the isotope effects in the Gd ion exchange processes involving complex forming reagents. The heavy isotope of ¹⁶⁰Gd was found to be enriched at the front boundary of Gd adsorption band and the lighter isotopes of 1MGd, ¹⁵⁶Gd and ¹⁵⁷Gd were enriched at the rear boundary in both cases of 20.1m elution with EDTA and 14 m elution with malic acid, as predicted in the theoretical relations. Observed separation coefficients are 4.9×10^?5, 4.0×10^?5 and 2.5×10^?5for isotopie pairs of ^{156 160}Gd, ¹⁵⁸Gd and ¹⁶⁰Gd, respectively, in the case of EDTA elution. In the case of malic acid elution, smaller separation coefficients were observed as 1.8×10^?5, 1.6 ⁵O^?5 and 0.92×10^?5 for isotopie pairs of ^{156 160}Gd, ¹⁵⁷Gd and^{158 160} respectively.     

Lithium Isotope Separation by Displacement Chromatography Using Cryptand Resin

This paper summarizes results of sensitivity analysis of a generic geologic disposal system for HLW, using a GSRW code and an automated sensitivity analysis methodology based on the Differential Algebra. The results of sensitivity analyses indicate that parameters related to a homogeneous rock surrounding a disposal facility have higher sensitivities to the performance measure analyzed here than those of a fractured zone and engineered barriers.

This methodology permits sensitivity analyses of a single parameter with changing values of other parameters simultaneously, and thus gives quantitative information on the interrelation- ship between the parameters: the parameters for engineered barriers are generally insensitive to the output, while they are somewhat sensitive to the output only in a case of the low solubility condition. The methodology also provides technical Information which might be basis for the optimization of design of the disposal facility.     

Uranium Isotope Exchange between Uranium Hexafluoride and Uranium Pentafluoride

To aim at a better understanding of the uranium isotope exchange reaction between gaseous UF₆ and solid UF₅ experiments were done with natural UF₆ gas and solid UF₅ containing 3% ²³⁵U under different pressures of UF₆. The experimental results suggest a two-process reaction with an initial rapid increase of ²³⁵UF₆ in the gas phase followed by its slight and gradual increase. A rate equation based on a collision model is given for the two-process reaction which includes a primary exchange reaction on the solid surface and a secondary reaction participated by underlying UF₅ molecules. An analytical solution is provided for both of ²³⁵UF₆ concentration in the gas phase and ²³⁵UF₅ concentration on the solid surface, which is useful for determining the parameters characterizing the exchange reaction. A numerical analysis is also made to evaluate the influence of gas samplings. A remarkable agreement is found between the particle sizes of UF₅ estimated from the reaction parameter and from the direct observation with an electron microscope. The depletion of ²³⁵UF₅ concentration by the exchange reaction is very small when averaged over the whole solid UF₅, because the depletion is virtually limited to the solid surface due to the small reaction probability of underlying UF₅ molecules.     

Separation of Uranium Isotope by Plasma Centrifuge

A method of centrifugal separation of isotopes by electromagnetic means is presented. The principle proposed utilizes electromagnetic acceleration by the interaction between an electric current in a slightly ionized gas and an external magnetic field. The analysis shows that an azimuthal flow of 2.6 km/sec can be realized with a magnetic field of 200 gauss and an electric current of 1.5kA. The resulting centrifugal force is large enough to permit realization of a more compact concentration cascade than the conventional mechanical centrifuge.     

Anomalous Isotope Fractionation in Uranium Enrichment Process

A benchmark calculation for a deep penetration problem of 14 MeV neutrons through a 3m thick iron slab was carried out by using a vectorized continuous energy Monte Carlo code MVP with the JENDL-3 and ENDF/B-IV cross sections. Reference solutions for neutron spectra and averaged cross sections were obtained at various locations through the iron slab with good statistics owing to a high computation speed of the code. The accuracy of multigroup calculations with the JSSTDL/J3 library was investigated by comparison with the obtained reference solutions.

Both calculations with JENDL-3 and ENDF/B-IV showed a similar attenuation of total fluxes from thermal to 14 MeV through the slab, while differences of one order at the maximum were observed in the calculated fluxes in the resonance energy region. The multigroup calculations with the JSSTDL/J3 295- and 125-group libraries underestimate the streaming effect through the cross section minima above the well-known 24 keV window, which resulted in the underestimation of fluxes above this window by more than two decades at 3 m penetration compared with the continuous energy method. Taking into account the spatial dependence of averaged cross sections, the underestimation was reduced to about one decade. It was found, however, that an accurate prediction of streaming effect is fairly difficult by the multigroup method.     

Hydrogen Isotope Separation by Self-displacement Chromatography Using Palladium Particles

Formation constants of a trivalent f-element, europium, with a series of carboxylates containing neutral donors such as amine and alcohol oxygen were determined by solvent extraction method in 0.1 M NaClO₄ at 25°C. Thirteen carboxylates were adopted for a systematic study of the effect of the functional groups on the complex stabilization. In order to analyze the trend of formation constants, a simple model was developed in which these ligand molecules were considered as composed of a certain number of fragment components of functional groups and chemical bridges each of which differently contributes to the formation constant. All parameter values for electrostatic and steric effects of the fragments were successfully determined by using the formation constants obtained experimentally. The present model is useful for predicting the formation constants of similar multidentate ligands by combining the fragment components and parameter values.     

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.     

TEVA-TEVA色层分离大量铀中的微量镎

建立了高效分离高铀镎比样品中微量镎的方法。采用TEVA-TEVA萃取色层柱分离铀产品中微量镎,经3.0 mol/L HNO₃淋洗过后以0.5 mol/L (NH₄)₂CO₃洗脱TEVA树脂上的镎,加入HNO₃分解洗脱液中的碳酸镎酰离子并将溶液调至3.0 mol/L HNO₃,进行TEVA柱二次分离,最后采用0.02 mol/L HNO₃-0.02 mol/L HF洗脱。结果表明：该法稳定性较好,测量相对标准偏差优于4%（n=3）,镎的平均回收率大于86%,铀的去污因子大于10⁵,适用于高铀镎比样品中微量镎的分离,在乏燃料后处理工艺中铀线尾端的微量镎分析中具有较好的应用前景。     

低温制备气相色谱法分离氢同位素

介绍了采用低温制备气相色谱法以Al2O3装填分离柱进行氢同位素分离的装置。研究了氢同位素分离色谱柱(Al2O3分离柱)的制备和操作步骤，并对其分离效果进行了讨论。实验结果表明：经分离、净化后，氘纯度可达99．9％以上。该装置具有结构简单、操作费用低、一次性投资少等优点，在那些对氢同位素纯度要求高，用量小的部门或实验室有良好的应用前景。该装置不仅可用于氢氘分离，还可用于氘氚分离。     

Uranium Isotope Exchange between Gaseous UF6 and Solid UF5

A new rate equation is derived for uranium isotope exchange reaction between gaseous UF₆ and solid UF₅ by assuming the total number of UF₅ molecules on the particle surfaces to depend on time. The reaction parameters included in the equation are determined from the experimental results, and are compared with the previous ones. The rate equation given in this work satisfies the related isotopic mass balance, and includes explicitly the terms related to the UF₆ density and the mean size of UF₅ particles, both of which cause an important effect on the reaction. Since the rate equation derived in this work facilitates the simulation of the reaction under various conditions, the long term behavior of a simulated exchange reaction is studied under the condition considered to be close to that in a recovery zone of the MLIS process.     

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.     

用再生铀生产低浓铀的一种离心法分离方案

将从乏燃料提取的再生铀返回到核燃料循环,对核能的可持续发展有重要意义。本文基于Q?模型级联,从分离级联规模、原料利用率、天然铀消耗等方面,对利用再生铀生产低浓铀的一种方案进行了深入优化分析。结果表明,生产相同量低浓铀情况下,消耗天然铀越少,原料利用率越高,乏燃料循环闭合指数越大,但级联的规模越大;用再生铀生产低浓铀的经济性需从天然铀消耗、级联规模、乏燃料循环闭合指数等多方面综合考虑。此结果还表明,本文提出的方案能满足完全乏燃料闭合循环要求,是简单且较理想的分离方案。     

Effect of Flow Rate on Height Equivalent to a Theoretical Plate for Lithium Isotope Separation with Displacement Chromatography

A series of experiments of Li isotope separation with displacement chromatography using a highly porous resin were performed under several flow rates from 0.1 to 20 cm³/min. The flow rates were equivalent to a speed of a moving boundary of 0.0012 to 0.26cm/s. In evaluating Height Equivalent to a Theoretical Plate, HETP, as well as separation factor which indicate separative performance of chromatographic system, we developed a new relationship between HETP and a profile of ⁶Li mole fraction in the effluent with a mathematical model taking account of a mixing in a free space at the column outlet and in the fractionated samples. The values of separation factor and HETP of each experiment were simultaneously determined by the developed relation. The obtained values of the separation factor agreed with those evaluated by the frontal analysis method within the range of the experimental error. The obtained value of HETP increased with the flow rate in the range of the present experiments. It was suggested that diffusion of Li ion in particles as well as convective mixing of the solution played a significant role on determination of HETP.     

Reduced Partition Function Ratio of Uranyl Ion and Uranium Isotope Effect

Density of 30v/o tri-n-butyl phosphate-n-dodecane solution loaded with uranyl nitrate, nitric acid and water was measured. An empirical density equation was derived from regression analysis of the density data. The equation represents the density values well in a wide range of composition and temperature.     

Nd同位素溯源铀矿石浓缩物产地研究

铀矿石浓缩物(UOC)是核法证学中溯源研究的核材料之一,通过测量其中Nd同位素丰度比能提供地理指示信息。本文基于TRU树脂对铀和稀土元素的吸附特性,通过条件实验获得了最佳淋洗酸度和体积,分离稀土元素和大量铀基体;利用LN树脂分离镧系元素的特性,分离具有同量异位素干扰的Sm,使用TRU和LN树脂联用方式有效分离了Nd,建立了一种能分离UOC中U、Sm和Nd的方法。应用该方法对UOC样品进行多次测量,洗脱液中U含量低于5 ng/g,有效实现了UOC中大量U与微量Nd的分离。采用多接收电感耦合等离子质谱对Nd同位素进行测量,测量精度达0.002%,满足Nd同位素测量需求。该方法已用于实际UOC样品中的Nd分离,并进行了初步溯源研究。     

天然甲烷与全氘甲烷同位素的色谱分离

采用四极质谱仪在线测定了CD4和CH4同位素色谱总分离度(K1)与色谱条件、进样量之间的关系。结果表明,K1受色谱柱填料、长径比和样品量影响较大,载气流速影响不明显,柱温的影响与色谱柱的填料有关。     

TEVA-UTEVA萃取色层分离后处理铀产品中镎的方法研究

本文建立了有效、定量分离后处理铀产品中镎的方法。该方法采用TEVA-UTEVA萃取色层分离后处理铀产品中的微量镎,先将镎调至四价后过TEVA萃取色层柱,再用2 mol/L HNO₃-0.2 mol/L H₂C₂O₄解吸吸附在TEVA树脂上的镎,最后将镎解吸液稀释后过UTEVA萃取色层柱进一步分离。结果表明,镎的平均全程回收率约为94%,铀的去污因子＞10⁴。     

气相色谱法在氢同位素分离中的应用

简要介绍了气相色谱法分离氢同位素的原理,重点阐述了利用气相色谱法分离氢同位素的几种主要工艺(洗提色谱法、氢置换色谱法、自置换色谱法和前沿置换色谱法)及其应用进展,并对气相色谱法在氢同位素分离中的应用前景进行了评述。