Uranium electrodeposition for alpha spectrometric source preparation

In this paper a simple method was used to design and set up an electrodeposition device for uranium source preparation for alpha spectrometry measurements. The aim of this work is to find the optimal parameters to be used to achieve uranium alpha sources with good spectral properties and maximum yield of the electrodeposition process. Samples with specific uranium activity were prepared from aqueous solution of uranyl nitrate hexahydrate (UO₂ (NO₃)₂·6H₂O). A series of preliminary experiments was conducted to establish the main parameters that have a significant influence on the deposition efficiency. Among these, the electrodeposition time was studied and the optimum time was found to be 1 h, in the case of our home-made deposition cell. It was also shown that a current of 1,500 mA, plating time of 60 min and pH range of 2–2.2 are the best conditions for deposition of uranium. The alpha spectrometry results show a good spectral resolution for the uranium sources obtained by the electrodeposition using the optimal parameters.     

Preparation of a one-curie <Superscript>171</Superscript>Tm target for the detector for advanced neutron capture experiments (DANCE)

Approximately one curie of ¹⁷¹Tm (T _1/2 = 1.92a) has been produced and purified for the purpose of making a nuclear target for the first measurements of its neutron capture cross section. Target preparation consisted of three key steps: (1) material production; (2) separation and purification; and (3) electrodeposition onto a suitable backing material. Approximately 1.5 mg of the target material (at the time of separation) was produced by irradiating ca. 250 mg of its stable enriched ¹⁷⁰Er lanthanide neighbour with neutrons at the ILL reactor in France. This production method resulted in a “difficult-to-separate” 1:167 mixture of near-neighboring lanthanides, Tm and Er. Separation and purification was accomplished using high-performance liquid chromatography (HPLC), with a proprietary cation-exchange column (Dionex, CS-3) and alpha-hydroxyisobutyric acid (α-HIB) eluent. This technique yielded a final product of ∼95% purity with respect to Tm. A portion (20 μg) of the Tm was electrodeposited onto thin Be foil and delivered to the Los Alamos Neutron Science Center (LANSCE) for preliminary analysis of its neutron capture cross section using the Detector for Advanced Neutron Capture Experiments (DANCE). This paper discusses the major hurdles associated with the separation and purification step, including scale-up issues related to the use of HPLC for material separation and purification of the target material from α-HIB and 4-(2-pyridylazo)resorcinol (PAR) colorant.     

Electrodeposition of milligram amounts of uranium on electropolished stainless steel disks

Investigations have been carried out for the electrodeposition of milligram amounts of uranium on electropolished stainless steel disks with an objective of preparing good quality sources for -spectrometric studies on uranium. The parameters studied include the variation of electrodeposition yield as a function of voltage, time, distance between the cathode and anode, and the volume of 0.2M ammonium oxalate solution. The conditions selected for preparing good quality sources with nearly 100% yield were: electrodeposition voltage 25 V, time of deposition 15 min, volume of 0.2M ammonium oxalate solution in the cell 4 ml and a distance of 2 cm between the cathode and anode. The sources prepared using this method have been used successfully for the -spectrometric determination of²³⁴U/²³⁸U ratios in uranium samples.     

An improved method for determination of uranium isotopic composition in urine by alpha spectrometry

A comparative study of source preparation techniques to determine uranium isotopic composition by alpha spectrometry, namely electrodeposition and chemical stripping with polymeric membranae containing trioctylphosphine oxide (TOPO), is presented. The mean yield obtained for electrodeposition and TOPO deposition were 85% and 74%, respectively. The mean activity ratio²³⁵U/²³⁸U were 0.044 and 0.042 and the ratio²³⁴U/²³⁸U were 0.994 and 1.009, using electrodeposition and TOPO deposition techniques, respectively. The method of uranium separation from urine using an ion-exchange resin Dowex 1×8, chloride form and citrate form, was also studied. The obtained global yields of these methods were 50% and 41%, respectively.     

Effect of cationic composition of melts M2WO4-M2W2O7-UO2WO4 (M = Li, Na, K, Cs) and parameters of electrolysis to uranium dioxide electrodeposition characteristics

The effect of solvent salt cation, temperature of electrolysis, and cathodic deposition potential to basic characteristics of uranium dioxide potentiostatic electrodeposition (cathodic current efficiency, current density, and product deposition rate) in electrolyte system M₂WO₄-M₂W₂O₇-UO₂WO₄ (M = Li, Na, K, Cs) was studied in air. A conclusion was made that optimum electrodeposition and production of deposits not contaminated with supporting electrolyte decomposition products need higher cathodic polarization close to the solvent decomposition potentials and higher temperatures (up to 900°C). A melt based on K₂WO₄ was selected as the electrolyte providing satisfactory electrodeposition parameters of uranium dioxide with the composition close to stoichiometric.     

Elektrolytische Uran-und Plutonium-Präparateherstellung für die Alpha-Spektrometrie aus Organischen Lösungen

A method for preparation of uranium-and plutonium-measuring probes for α-spectrometry is described. The method is based on electrodeposition from isopropanol and especially from ethanol and methanol solution. It was shown that a definite addition of a little amount of water lead to an increasing of the deposition speed by ethanol and methanol. It is possible to reach in ethanol a 100% deposition grade after an electrolysis time of 3 minutes for uranium and 30 minutes for plutonium with voltages of 150–200 V.      

Fe-Ni-S软磁薄膜的电沉积

酸性镀液中以硼酸为缓冲剂、柠檬酸三钠为配合剂,在紫铜箔上电沉积得到非晶Fe-Ni-S合金薄膜。 采用扫描电子显微镜和能谱分析技术(EDS)研究了镀液组成和沉积条件对镀层表面形貌和组成的影响。 结果表明,在镀液中加入2 g/L C7H5O3NS（糖精）和0.4 g/L 1,4-丁炔二醇可获得表面平整无裂缝和较小内应力的合金镀层;电流密度和镀液pH值对镀层组成影响较小,但施镀温度对镀层组成影响较大。 获得了理想的镀液组成和沉积条件,所得Fe73Ni9.5S17.5薄膜的X射线衍射表明其为非晶结构,在室温下具有较高的饱和磁化强度(Ms约为876.25 kA/m)和较低的矫顽力(Hc约为4.96 kA/m),具有良好的软磁性能。 循环伏安曲线和阴极极化曲线均表明,镀液中CS(NH2)2会促进Fe-Ni-S共沉积。     

Electrochemical synthesis of nano-cobalt hexacyanoferrate at a sol–gel-coated electrode templated with β-cyclodextrin

The paper describes the time-dependent evolution of the electrochemical deposition of cobalt hexacyanoferrate (CoHCFe) on graphite foil electrode modified with electrochemically formed sol–gel film doped with β-cyclodextrin to impart porosity. With short-time electrodeposition, cyclic voltammetry (CV) shows a single redox couple typical of nano-sized clusters of CoHCFe, while at longer deposition times the CV’s shape evolves to the classical form of a bulk compound in which there are present two redox couples. The electrode modified with β-cyclodextrin (CD) included in the sol–gel film has an active surface that corresponds to pores created by CD stacks normal to the surface. Hence, the electrochemical formation of CoHCFe starts in these conductive pores; only at long deposition times do the clusters overlap to form moieties with the voltammetric characteristics of bulk CoHCFe.     

Electrodeposition and determination of nano-scale uranium and plutonium using alpha-spectroscopy

Summary A simple method was used to design and set up an electrodeposition device for the alpha-emitting nuclides. The designed electroplating facility is leak proof and simple in operation and dismantled. The effect of current, pH of electrolyte, and the plating time on the electrodeposition efficiency have been investigated in a sodium bisulphate, sulphuric acid electrolyte in order to determine the optimum conditions. It was shown that a current of 900-1000 mA, plating time of 80-90 minutes and pH range of 2-2.3 are the best conditions for deposition of nano-scale uranium and plutonium. In these circumstances, it was possible to deposit 0.004 ng ^. g^-1 Pu and 60 ng ^. g^-1 U in an electroplating planchette. The device and modified procedures were successfully applied for soil samples. Prior to electrodeposition of the elements, a column extraction chromatography has been used to separate the Pu and U and eliminate most matrix and interferences in environmental samples.     

Preparation of targets for nuclear chemistry experiments at DANCE

In this paper, we describe the separation chemistry and electrodepositions conducted for the preparation of ²⁴¹Am, ²⁴³Am and ²³³U targets used for cross-section measurements at DANCE. Thick, adherent deposits were prepared using molecular plating from isopropyl alcohol solutions. Improved yields and thicknesses were observed for ²⁴¹Am electrodeposition after the material was purified using TRU resin from Eichrom. Similarly, ²³³U deposits were improved after purification with an anion exchange column in 9 M HBr followed by purification using UTEVA resin from Eichrom.     

Application of neutron activation analysis in a fission molybdenum separation study

The separation of⁹⁹Mo from low-enriched uranium (LEU, 19.5%²³⁵U) targets was evaluated using natural uranium (NU) and non-radioactive tracers. Neutron activation analysis was used to determine (1) the efficiency of molybdenum recovery and (2) the decontamination factor of numerous fission product elements from the molybdenum product. Using NU and non-radioactive elements simplified procedures and allowed tests to be completed in a fume hood instead of a shielded cell. During activation of the non-radioactive tracers, uranium fission occurs, which can interfere with subsequent gamma-ray analysis. A comparison was made of the interferences caused by these fission products from both NU and LEU.     

Electrode processes of uranium ions and electrodeposition of uranium in molten LiCl-KCl

In the first part, LiCl-KCl-UCl₃ and LiCl-KCl-UCl₃-UCl₄ molten salts were prepared, which were studied employing cyclic voltammetry and chronopotentiometry techniques, respectively. It was determined that the reduction of U(IV) to uranium metal takes two steps. Firstly, U(IV) is reduced to U(III). Then, the reduction of U(III) to uranium metal occurs in a step with a global exchange of three electrons. Cyclic voltammetry studies indicated that at low sweep rates, the reduction of U(III) to uranium is reversible. However, a mixed control of both diffusion and electrontransfer is observed as the sweep rate increases. The diffusion coefficient of U(III) and the formal potential of U(III)/U versus Ag/AgCl reference electrode in these two salt systems were calculated respectively. In second part, based on the data of the electrode processes of uranium ions, electrodeposition of uranium metal was carried out. Uranium deposits were prepared adopting a 304 stainless steel electrode in the molten LiCl-KCl-UCl₃ and LiCl-KCl-UCl₃-UCl₄, respectively by employing suitable electrolytic techniques. The morphology of the deposits and the cross-section of the cathode were investigated by SEM. It was determined that at the beginning of the deposition process, uranium product alloys with stainless steel and forms a thin layer, and then uranium begins to grow adhering to the layer.     

Use of multivariate and neutron activation analysis on studying element interrelationships in Brazilian phosphorite

Methods to determine U, Th, and other constituent elements in mineral matrices through Instrumental Neutron Activation Analysis (INAA), have been widely utilized due to their capability to extract a large quantity of information from small samples. In the present work, an experimental methodology based on INAA associated to the cluster statistics technique was used to determine the uranium concentration and its correlation with other elements present in the mineral phosphorites from the northeast region of Brazil. Data for 22 elements including rare-earth elements are presented. A good correlation between uranium and rare-earth elements is observed. For the transition metals, correlation with uranium was not noted.     

电沉积CdTe多晶薄膜光电化学电池的初步研究

采用电沉积工艺,在黄铜衬底上阴极电沉积多晶CdTe薄膜,并用它作为光电极,Cu₂S作为对电极,多硫氧化还原体系Na₂S+NaOH+S溶液为电解液制作光电化学电池,测量电池的J_sc、V_oc和I～V特性曲线并计算了效率和填充因子F_F,对影响电池效率的几种因素作了关联和讨论。     

Determination of uranium in salt solutions containing high levels of lanthanides via epithermal neutron activation analysis

Epithermal Instrumental Neutron Activation Analysis has been used to measure the concentration of uranium in eutectic salt solutions in support of a research program in which the actinide elements are separated from rare earths and other fission products using high-temperature electo-deposition. The uranium response over three decades in concentration follows a negative power function; and high concentrations of samarium interfere with the determination of uranium but can be accurately corrected. The EINAA method was successfully used to analyze NIST SRM 278 Obsidian and NIST SRM 1566a Fly Ash.     

Electrodeposition of americium and observation of the surface by means of alpha particle tracks on a cellulose nitrate film

The optimum conditions for high electrodeposition yields of trace amounts of americium on a stainless steel plate and an aluminium foil were studied. In the case of a stainless steel cathode, the following conditions can be recommended: electrolyte, 10 ml of a 0.1M ammonium oxalate buffer solution with 0.5 ml of the americium stock solution (7∶93 v/v, HNO₃); current density, 86 mA/cm²; deposition time, 60 min. The uniformity of the deposited²⁴¹Am was examined with a conventional α-track method with a cellulose nitrate film as a track recording material. Clear tracks on this film were obtained with a polyester film (18 μ) as α-absorber placed between the deposited americium source and the cellulose nitrate film.     

Determination of traces of rare earth elements in high-purity uranium by ion-exchange separation and neutron activation γ-spectrometry

Neutron activation γ-spectrometry is sufficiently sensitive for the determination of traces of rare earth elements but quantitative separation from uranium is essential. The rare earth elements in 0.2 M ammonium carbonate medium are quantitatively retained on Chelex-100, and are quantitatively separated from uranium by recycling the eluate. When 10-g samples are used, neutron activation provides detection limits of 1–20 μg kg^?1. Recoveries of rare earths, checked by spiking with radiotracers, are essentially complete.     

Optimal parameters for the electrodeposition of uranium

Some remarks are given comparing two recently published methods of electrodeposition of uranium on stainless steel planchets to prepare sources for -spectrometry. Parameters used in the two procedures are discussed, and a general method of determining the best electrodeposition yield is proposed.     

电沉积法制备固态染料敏化太阳能电池

本文采用一步电化学沉积的方法在导电玻璃上先后沉积了ZnO/染料复合薄膜以及CuSCN薄层,实现仅以电沉积法制备结构为ZnO/染料/CuSCN的固态染料敏化太阳能电池,电池的光电转换效率达到0.1%.在电沉积CuSCN前,脱附电沉积制备的ZnO/染料复合薄膜中的染料以形成多孔ZnO薄膜,然后通过染料再吸附得到染料敏化ZnO纳晶多孔薄膜.在电沉积过程中,ZnO和CuSCN的晶体尺寸、晶体取向和膜层形貌都可以进行比较精准的控制.探讨了影响沉积薄膜形貌和光电转换效率的因素,如旋转圆盘电极的旋转速度、电沉积温度以及染料敏化剂的选择.本文报道的低温电沉积制备全固态太阳能电池的方法为制备柔性染料敏化太阳能电池提供了一种新的思路.     

A high resolution 4π alpha spectrometer with silicon surface barrier detectors

An alpha counting system has been designed which gives counting geometry of nearly 4π with resolution capabilities of 25 keV or better. The alpha source is electro-deposited onto a thin gold foil which is sandwiched between two silicon surface barrier detectors. Alpha pulses from the two detectors are amplified, normalized and summed as a single pulse height spectrum. The techniques for the electrodeposition of the alpha activity onto the thin gold foil are described.