用ICP-AES法测定三碳酸铀酰铵中的钛

采用ICP-AES法测定三碳酸铀酰铵中杂质钛的含量。硝酸分解样品、色层柱分离铀基体后,用ICP-AES法测定钛。方法加标回收率为95.2%～99.5%,RSD小于4.10%。方法简便、快速,可满足三碳酸铀酰铵中钛含量的例行分析要求。     

ADU&AUC的还原设备

本文叙述了由 ADU＆AUC 转换成 UO_2 的基本原理和要求,介绍了自制的几种不同结构的还原设备和它们的使用效果.     

碳纳米管小球型材吸附铀酰离子的性能研究

以聚苯乙烯树脂小球为前驱体,采用气相沉积法合成了碳纳米管小球型材,将其应用于对放射性废水中铀酰离子的吸附。测试结果显示,当pH处于4~8时,吸附量达到最大值。铀酰离子的吸附为Langmuir单层吸附,理论最大吸附量为73.42 mg/g。同时吸附动力学分析表明,该吸附为拟二级化学吸附。     

硝酸铀酰溶液中不锈钢电极表面沉积氧化膜的行为研究

用动电位极化法研究了不锈钢(1Crl7)电极在NaCl-UO2(NO3)2溶液中的电化学行为．在阴极反应区。由于氢的不断释放，导致铀酰离子在不锈钢电极上析出．随着极化电位向阳极区移动，不锈钢电极发生阳极氧化。形成了氧化铀沉积膜．SEM对析出物和沉积膜的形貌进行了分析．AES深度剖析沉积膜的厚度约为40nm．XPS分析证实不锈钢腐蚀电极表面沉积膜中铀为U(Ⅵ)．     

Recovery of uranium from low-grade ore using microorganism isolated from uraniferous rock sample

Bioleaching, in the scope of biotechnology, is one of the promising technologies, which can be utilized for extracting valuable radioactive metal (uranium) from other radioactive ones. Also, it considered as an economical way to recover uranium from low-grade ores after the depletion of high grade uranium deposits. The aim of the work is to explore the formation and composition of the bioprecipitate from low-grade uraniferous rock sample through the bioleaching process using fungi. Furthermore, to identify the radionuclides distribution during work stages using the Hyper Pure Germanium detector. The results showed that; Aspergillus niger accomplished 71.4% of uranium recovery, as well as, formation of stable organo-uranyl complex. The obtained bioprecipitate, composed of ″uranyl acetate hydrate,″ asserted that the uranium is nearly free from other radionuclides present in the original sample without any subsequent purification processes, whereas could not achieved by the conventional process of uranium recovery.     

Photochemical Reaction of Bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) (tetrahydrofuran)dioxouranium(VI) in Supercritical Carbon Dioxide

The emission lifetime of bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(teterahydrofuran)dioxouranium(VI) complex, UO₂(hfac)₂thf, has been measured in sub and supercritical carbon dioxide (sc-CO₂) under the conditions of 10 to 60 MPa and 293.2 to 340.2 K. It was found that the decay rate constants of excited UO₂(hfac)₂thf species (*UO₂(hfac)₂thf) decrease with increasing the pressure of sc-CO₂. The rate constants for quenching reactions of *UO₂(hfac)₂thf with alkenes in sc-CO₂ were determined as 4.32×10⁹(for cyclohexene), 3.04×10⁹(for cycloheptene), 2.13×10⁹(for 1-octene), and 3.801×10⁸mol^-1·dms^-1·s^-(for 1-hexene). The activation volumes for the quenching reactions of *UO₂(hfac)₂thf with cyclohexene, cycloheptene, 1-octene, and 1-hexene at 308.2 K were determined to be 16.7, 28.7, 16.7, and 24.7cm³.mol^-1, respectively.     

Kinetic Parameter βeff/ℓ Measurement on Low Enriched Uranyl Nitrate Solution with Single Unit Cores (600𝛗;, 280T, 800𝛗;)of STACY

The kinetic parameter β_eff/? of low enriched (10% EU) uranyl nitrate solution was measured by the pulsed neutron source (PNS) method in STACY This measurement was repeated systematically over several uranium concentrations from about 195 gU/l to about 430 gU/l. Used core tanks were two cylindrical tanks whose diameters are 600 mm and 800 mm and one slab tank which has 280 mm thickness and 700 mm width. In this report, experimental data such as solution conditions, critical solution level for each solution condition, subcritical solution levels where measurements were conducted, measured decay time constants of prompt neutron and extrapolated β_eff/? values are described as well as basic principle of the PNS method. The kinetic parameter β_eff/? values were evaluated also by computation with the diffusion code CITATION in SRAC and the nuclear data library JENDL 3.2. Strong linear correlation has been found between kinetic parameter β_eff/? and uranium concentration regardless of differences of reflecting conditions or core tank conditions. Experimentally or computationally evaluated β_eff/? value is about 90 s^-1 at 195 gU/l and about 170 s^-1 at 430 gU/l and both experimental and computational values show good agreement within an error of 3% which is comparable to about 2% uncertainty of measurement.     

Uranyl ion binding properties of poly(hydroxamic acid) hydrogels

Summary   Poly(hydroxamic acid) (PHA) hydrogels, obtained from the synthesis of crosslinked poly(acrylamide) (PAAm) gels have been prepared, and their uranyl ion binding properties from two different sources were investigated. Swelling and binding parameters of crosslinked PHA gels were determined from swelling and uranyl ion adsorption studies. The effect of uranyl ion concentration, pH, temperature and mass of adsorbent on the uranyl ion adsorption were examined. The binding process between PHA and uranyl ions complies with the S type adsorption according to Giles classification. Free energies of the adsorptions found as negative values indicating spontaneous adsorption process. The structure and hydrophilicity of the used crosslinkers, the ionogenity of PHA polymers and the source of uranyl ions found to be effective on the swelling and binding behaviors of PHA hydrogels. Received: 3 March 2001 / Revised version: 30 June 2001 / Accepted: 9 July 2001     

In-situ Measurement of UO2 2+ Concentration in Molten NaCl-2CsCl by Differential Pulse Voltammetry

In order to assess the applicability of the Differential Pulse Voltammetry technique to the in-situ measurement of UO₂ ²⁺ concentration in the oxide electro-winning process, DPV measurements for UO₂Cl₂ in molten NaCl-2CsCl were studied. DPV measurement of UO₂ ²⁺ in NaCl-2CsCl at 923 K, with a set of optimized parameters (potential sweep rate ?0.1 V/s, pulse cycle 0.1 s, pulse width 10 ms and pulse potential height 50 mV), showed a clear current peak at ?0.9 V vs. Cl₂/Cl^?. This was attributed to the reduction of UO₂ ²⁺ to UO₂ ⁺. The relation between the current peak height and the analytical concentration of the UO₂ ²⁺ showed good proportionality in the concentration region up to 0.06 mol.l ^?1, and the applicability of UO₂ ²⁺ concentration measurement by DPV was confirmed up to 0.4 mol.l ^?1. In order to assess the interference by the coexisting fission product elements to the measurement of UO₂ ²⁺ concentration, DPV measurements of UO₂ ²⁺ concentration in molten NaCl-2CsCl containing PdCl₂, NdCl₃, SmCl₃ and CeCl₃ were also performed. Even before removing Pd, the current peak at ?0.9 V vs. Cl₂/Cl^? by the reduction of UO₂ ²⁺ to UO₂ ⁺ was found to be distinguishable from the reduction currents of Pd²⁺ to Pd at ?0.7 V vs. Cl₂/Cl^?. As a result, the application of DPV measurement technique to the in-situ monitoring of UO₂ ²⁺ concentration in the oxide electro-winning method requires the improvement of the DPV measuring condition or the electrode structure on higher UO₂ ²⁺ concentration condition.     

Criticality Safety Benchmark Experiment on 10% Enriched Uranyl Nitrate Solution Using a 28-cm-Thickness Slab Core

The second series of critical experiments with 10% enriched uranyl nitrate solution using a 28-cm-thick slab core have been performed with the Static Experiment Critical Facility of the Japan Atomic Energy Research Institute. Systematic critical data were obtained by changing the uranium concentration of the fuel solution from 464 to 300 gU/l under various reflector conditions. In this paper, the thirteen critical configurations for water-reflected cores and un reflected cores are identified and evaluated. The effects of uncertainties in the experimental data on k ^eff are quantified by sensitivity studies. Benchmark model specifications that are necessary to construct a calculational model are given. The uncertainties of k _eff's included in the benchmark model specifications are approximately 0.1%δk _eff. The thirteen critical configurations are judged to be acceptable benchmark data. Using the benchmark model specifications, sample calculation results are provided with several sets of standard codes and cross section data.