Effect of complexing anions on sorption of U(VI), <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous solutions on layered double hydroxides of Mg,Al, and Nd

Sorption of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on Mg-Al and Mg-Nd layered double hydroxides (LDHs) in various forms was studied. The distribution coefficients K _d of U(VI) and ⁹⁰Sr on LDH-Mg-Al-EDTA are 100–120 ml g⁻¹ in 15 min of contact of the solid and liquid phases at V/m = 50 ml g⁻¹. At the same time, under similar conditions, U(VI) and ⁹⁰Sr are not sorbed from aqueous solutions on LDH-Mg-Al-C₂O₄. The sorption of U(VI) from aqueous solutions containing H₂EDTA²⁻, C₂O₄²⁻, and CO₃²⁻ on LDH-Mg-Nd-CO₃ and LDH-Mg-Al-CO₃ strongly depends on the concentration of the complexing anions in the solution. In particular, for 10⁻³ M aqueous UO₂²⁺ solutions, with an increase in [C₂O₄²⁻] from 10⁻³ to 5 × 10⁻² M, K _d of U(VI) decreases from >5 × 10³ to 70 ml g⁻¹ for LDH-Mg-Al-CO₃ and from 170 to ∼0 ml g⁻¹ for LDH-Mg-Nd-CO₃. In the presence of 10⁻³ to 5 × 10⁻² M CO₃²⁻ in aqueous solution, U(VI) is not noticeably sorbed on LDH-Mg-Nd-CO₃ (K _d does not exceed 16 ml g⁻¹ at V/m = 50 ml g⁻¹), and on LDH-Mg-Al-CO₃ the sorption sharply decreases (K _d decreases from >5 × 10³ to ∼0 ml g⁻¹ at V/m = 50 ml g⁻¹). The presence of complexing anions in the solution does not appreciably affect the ⁹⁰Sr sorption, but noticeably affects the 90Y sorption. With an increase in their concentration, K _d of ⁹⁰Y appreciably decreases. The effect exerted by Sr²⁺ ions on the sorption of microamounts of U(VI) and by UO₂²⁺ ions on the sorption of microamounts of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on LDH-Mg-Nd-CO₃ was also examined.     

Reactor production and purification of <Superscript>153</Superscript>Sm radioisotope via <Superscript>nat</Superscript>Sm target irradiation

Neutron irradiation of a natural Sm target is performed to produce ¹⁵³Sm. Ion-exchange chromatography is used to separate ¹⁵³Sm from Eu radionuclides produced in the process. To prepare a target, Sm₂O₃ powder is dissolved in 0.2 ml of HNO₃ in a quartz vial. Samarium is deposited onto the vial walls by passing nitrogen gas at 120°C. The prepared samarium target is encapsulated in aluminum foil and irradiated in a 5-MW reactor in 5 × 10¹³ n cm⁻² s⁻¹ flux. The irradiated target is dissolved in 1 M HCl, and the produced radioisotopes are determined with an HPGe nuclear detector. Finally ¹⁵³Sm is separated from Eu radionuclides with ¹⁵³Sm recovery yield of more than 66% and purity better than 99.8%.     

Effect of Pr<Superscript>3+</Superscript> on the stokes luminescence of YPO<Subscript>4</Subscript>:Nd<Superscript>3+</Superscript> under IR excitation

We have identified general relationships between the spectral and kinetic properties of the IR Stokes luminescence bands of Y_{1 − x − y} Nd _x Pr _y PO₄ solid solutions in the spectral range 0.86–1.40 μm under 0.810-μm laser excitation. The results have been used to formulate technical requirements for the purity of rare-earth oxides for the fabrication of efficient YPO₄:Nd³⁺ IR phosphors and to develop a fast YPO₄:Nd³⁺, Pr³⁺ IR phosphor that allows the decay time of the Nd³⁺ IR Stokes luminescence bands in the range 0.86–1.40 μm to be tuned from 50 to 170 μs by varying the ratio of the Nd³⁺ and Pr³⁺ concentrations.     

Extraction of single <Superscript>71</Superscript>Ge atoms from the gallium target of a Ga-Ge neutrino detector

A method has been developed for the extraction of single ⁷¹Ge atoms from the gallium target of a Ga-Ge neutrino detector. The key features of this chemical process stem from the extremely low content of the element to be extracted in the sample (n × 10⁻²⁷ at %), the large sample weight (up to n × 10³ kg), the limited time available for the extraction and measurement of the extracted atoms (≤20 h), and small permissible loss (≤0.1%) of the target material at high degrees of ⁷¹Ge extraction (≥90%). The method involves forced generation and maintenance of a disperse system of liquid gallium droplets with an oxide surface film in an acid-peroxide solution. The small droplet size ensures a rapid ⁷¹Ge transfer from the bulk target to a small amount of gallium oxide. The ⁷¹Ge passes from the oxide film to the solution, is concentrated, and converts to germane, which is delivered to a proportional counter. We have assessed the completeness of germanium extraction in relation to process conditions. The results, in particular the completeness of extraction, have been verified in experiments with Ga + Ge mixtures at germanium concentrations of 10⁻⁴ and 10⁻¹⁷ to 10⁻¹⁶ wt %. The adequacy of the approaches used to develop the technology of the Ga-Ge detector is supported by satisfactory agreement between the solar neutrino fluxes obtained with gallium and gallium-chloride detectors.     

Electrical properties of V<Subscript>2</Subscript>O<Subscript>5</Subscript>-CaO-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses exhibiting majority charge carrier reversal

The thermoelectric power and d.c electrical conductivity of x V₂O₅⋅40CaO⋅(60−x)P₂O₅ (10 ≤ x ≤ 30) glasses were measured. The Seebeck coefficient (Q) varied from +88 μ V K⁻¹ to −93 μV K⁻¹ as a function of V₂O₅ mol%. Glasses with 10 and 15 mol% V₂O₅ exhibited p-type conduction and glasses with 25 and 30 mol% V₂O₅ exhibited n-type conduction. The majority charge carrier reversal occurred at x = 20 mol% V₂O₅. The variation of Q was interpreted in terms of the variation in vanadium ion ratio (V^{5 +}/V^{4 +}). d.c electrical conduction in x V₂O₅⋅40CaO⋅(60−x)P₂O₅ (10 ≤ x ≤ 30) glasses was studied in the temperature range of 150 to 480 K. All the glass compositions exhibited a cross over from small polaron hopping (SPH) to variable range hopping (VRH) conduction mechanism. Mott parameter analysis of the low temperature data gave values for the density of states at Fermi level N (E_F) between 1.7 × 10²⁶ and 3.9 × 10²⁶ m⁻³ eV⁻¹ at 230 K and hopping distance for VRH (R_VRH) between 3.8 × 10⁻⁹m to 3.4 × 10⁻⁹ m. The disorder energy was found to vary between 0.02 and 0.03 eV. N (E_F) and R_VRH exhibit an interesting composition dependence.     

Synthesis and properties of AgTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-based NASICON-type phosphates doped with Nb<Superscript>5+</Superscript>, Zr<Superscript>4+</Superscript>, and Ga<Superscript>3+</Superscript>

We have synthesized materials based on a silver titanium phosphate with partial substitution of tri-, tetra-, or pentavalent cations for titanium: Ag_1±x Ti_2−x M _x (PO₄)₃ (M = Nb⁵⁺, Ga³⁺) and AgTi_2−x Zr _x (PO₄)₃. The materials have been characterized by X-ray diffraction and impedance spectroscopy and have been shown to have small thermal expansion coefficients. Their ionic conductivity has been determined. Silver ions in these materials are difficult to replace with protons.     

Recovery of <Superscript>131</Superscript>I and <Superscript>137</Superscript>Cs from a solution simulating NPP trap waters

Sorption of ¹³¹I and ¹³⁷Cs from a solution simulating NPP trap waters on various inorganic and organic sorbents was studied. The highest degree of ¹³¹I recovery (>99%) can be attained with Fizkhimin granulated sorbents based on coarsely porous silica gel containing Ag and Ni in 1: 4 ratio, with K _d for ¹³¹I exceeding 10⁵ ml g⁻¹ at V/m = 10³ ml g⁻¹ and contract time of the solid and liquid phases of 120 min. Elevation of the solution temperature to 40°C does not affect the degree of ¹³¹I and ¹³⁷Cs recovery. The degree of ¹³⁷Cs recovery in all the experiments did not exceed 35%. The degree of ¹³¹I recovery by coprecipitation with AgCl and Ag₄[Fe(CN)₆] was about ∼96% and only 65%, respectively.     

Using computer simulation techniques to design a tellurium-123 target for <Superscript>123</Superscript>I production

The production of ¹²³I from ¹²³Te by the ^l23Te(p, n)¹²³I reaction at various target enrichments (99.9, 91, 85.4, and 70.1%) was simulated using ALICE and SRIM programs. The ¹²³I production feasibility by the above reaction was evaluated. The calculations give more accurate results for proton beam energy of less than 30 MeV. The cross sections of all tellurium reactions with proton were calculated at 0–30 MeV proton beam energy with ALICE program, and the yield of ¹²³I was calculated by analytical methods. Our prediction for ¹²³I production via bombardment of ¹²³Te (99.9%) with a proton beam energy of 5–15 MeV is about 7.2 mCi μA⁻¹ h⁻¹. Published in Russian in Radiokhimiya, 2008, Vol. 50, No. 5, pp. 460–463. The text was submitted by the authors in English.     

Luminescence properties of monodispersed spherical BaWO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> microphosphors for white light-emitting diodes

Monodispersed spheres (1–4 μm in diameter) of BaWO₄:Eu³⁺ (hereafter BWO:Eu) red-phosphor exhibiting intense emission at 615 nm were synthesized via a mild hydrothermal method. X-ray diffraction, scanning electron microscope, photoluminescence excitation and emission spectra, and decay curve were used to characterize the properties of BWO:Eu phosphors. An intense red emission was obtained by exciting either into the ⁵L₆ state with 394 nm or the ⁵D₂ state with 465 nm, that correspond to two popular emission lines from near-UV and blue LED chips, respectively. The values of Ω _2,4 experimental intensity parameters (13.8 × 10⁻²⁰ and 8.2 × 10⁻²⁰ cm²) are determined. The high-emission quantum efficiency of the BWO:Eu phosphor suggests this material could be promising red phosphors for generating white light in phosphor-converted white light-emitting diodes.     

Sorption of Cs,Sr, and Y radionuclides on mixed layered double hydroxides of Mg,Al, and Nd from the aqueous phase

Sorption of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y radionuclides from aqueous solutions on the solid phase of layered double hydroxides (LDHs) of Mg, Al, and Nd was studied. Sorption of ¹³⁷Cs from 10⁻⁵ M aqueous CsNO₃ solutions on the LDH-Mg-Al-Nd solid phase is extremely weak. At the same time, ⁹⁰Sr and ⁹⁰Y are efficiently sorbed on the LDH-Mg-Al-Nd solid phase from 10⁻⁵ M aqueous Sr(NO₃)₂ solutions. After 5-min contact of the solid and liquid phases, K _d of ⁹⁰Sr and ⁹⁰Y exceeds 10³ ml g⁻¹. With an increase in the Nd content in LDHs of mixed composition, their sorption properties toward ⁹⁰Sr and ⁹⁰Y are enhanced.     

Adsorption of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc on aluminum oxide

Adsorption of ^99m Tc under static and dynamic conditions on aluminum oxides subjected to various acid treatments at pH from 7.29 to 1.26 (until the reaction of the oxide with the acid fully ceased) was studied. In batch experiments, the maximal adsorption of ^99m T_c, more than 30% of the radionuclide activity, is attained with the oxide that absorbed 2 × 10⁻⁴ mol g⁻¹ acid. The “rate” of linear migration of ^99m T_c in a chromatographic column in the course of elution with a 0.9% NaCl solution under the conditions of limiting saturation of the oxide with the acid is 0.49–0.52 cm ml⁻¹. It is concluded that the observed deceleration of the ^99m T_c elution from the generator column is due to its “braking” by active sites of the oxide. Upon reduction of ^99m T_c with bivalent tin, its adsorption increases to 93.53%. The results obtained are of interest for the development of procedures for depositing ^99m T_c onto the surface of nanosized colloidal particles of aluminum oxide for their subsequent use in medical diagnostics.     

Coprecipitation of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous and organic solutions with triethylenediamine complexes of <Emphasis Type="Italic">d</Emphasis>-element nitrates

Coprecipitation of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y with low-soluble complexes of nitrates of d elements (Cu²⁺, Ni²⁺, Zn²⁺) with triethylenediamine [(CH₂-CH₂)₃N₂] from aqueous and aqueous-organic solutions was studied. ¹³⁷Cs and ⁹⁰Sr do not noticeably coprecipitate with precipitates of complexes of Cu²⁺, Ni²⁺, and Zn²⁺ with (CH₂-CH₂)₃N₂ in water; in the process, the radionuclide recovery into the precipitate phase does not exceed 10%. At the same time, the degree of recovery of ⁹⁰Y reaches 65% depending on the experimental conditions. In C₂H₅OH and CH₃CN containing 9 and 5% H₂O, respectively, ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y coprecipitate with the complexes to a greater extent, with the degree of recovery varying from 30 to 97% at the molar ratio M²⁺: (CH₂-CH₂)₃N₂ = 1 : 1.     

Low-loss,high-purity (TeO<Subscript>2</Subscript>)<Subscript>0.75</Subscript>(WO<Subscript>3</Subscript>)<Subscript>0.25</Subscript> glass

By melting a mixture of high-purity oxides in a platinum crucible under flowing purified oxygen, we have prepared (TeO₂)_0.75(WO₃)_0.25 glass with a total content of 3d transition metals (Fe, Ni, Co, Cu, Mn, Cr, and V) within 0.4 ppm by weight, a concentration of scattering centers larger than 300 nm in size below 10² cm⁻³, and an absorption coefficient for OH groups (λ ∼ 3 μm) of 0.008 cm⁻¹. The absorption loss in the glass has been determined to be 115 dB/km at λ = 1.06 μm, 86 dB/km at λ = 1.56 μm, and 100 dB/km at λ = 1.97 μm. From reported specific absorptions of impurities in fluorozirconate glasses and the impurity composition of the glass studied here, the absorption loss at λ ∼ 2 μm has been estimated at ≤100 dB/km. The glass has been drawn into a glass-polymer fiber, and the optical loss spectrum of the fiber has been measured.     

Synthesis and luminescence properties of Eu<Superscript>2+</Superscript>-doped Li<Subscript>2</Subscript>SrSiO<Subscript>4</Subscript>

We have studied the luminescence spectra of Li₂Sr_{1 − x} Eu _x SiO₄ (x = 0.0001–0.01) solid solutions prepared by solid-state reactions and a sol-gel process in a reducing atmosphere. The spectra show a broad band in the range 500–700 nm, centered at 578 nm, which is due to the 4f ⁶5d → 4f ⁷ transition. The luminescence excitation spectrum shows, in addition to bands due to Eu²⁺ 4f ⁷ → 4f ⁶5d transitions, a strong band centered at 174 nm, attributable to absorption in the SiO₄⁴⁻ group.     

Coprecipitation of Trace Amounts of <Superscript>137</Superscript>Cs and <Superscript>85</Superscript>Sr with [Na(18-Crown-6]BPh<Subscript>4</Subscript> from Neutral and Alkaline Solutions

Coprecipitation of ¹³⁷Cs and ⁸⁵Sr with [Na(18-crown-6]BPh₄ solid phase from aqueous, aqueous-ethanolic, and alkaline solutions is studied. ¹³⁷Cs and ⁸⁵Sr cocrystallize with [Na(18-crown-6]BPh₄ from aqueous and aqueous-ethanolic solutions. The cocrystallization coefficients D of ¹³⁷Cs and ⁸⁵Sr from aqueous solutions are 2.6±0.5 and 3.3±0.3, respectively. For aqueous-ethanolic solutions, the corresponding values are 4.4±0.5 and 3.4±0.4. In the alkaline solutions (0.1 and 1 M NaOH), 54–74% of ¹³⁷Cs and 37–51% of ⁸⁵Sr pass into the [Na(18-crown-6]BPh₄ solid phase, depending on the crown ether concentration in the system.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 257–260.Original Russian Text Copyright © 2005 by Kulyukhin, Konovalova, Rumer, Kamenskaya, Mikheev.     

Synthesis and photoluminescence properties of LiEu(W,Mo)<Subscript>2</Subscript>O<Subscript>8</Subscript>:Bi<Superscript>3+</Superscript> red-emitting phosphor for white-LEDs

LiEu_1−x (W_2−y Mo _y )O₈:xBi³⁺ series red-emitting phosphors were synthesized by solid state reaction. The structure, morphology, and photoluminescent properties of phosphors were studied by X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectrum, respectively. X-ray powder diffraction analysis showed that the as-obtained phosphors belong to the scheelite structure. The average particle size of the investigated phosphor was about 8 μm. The excitation spectrum exhibits a charge-transfer broad band along with some sharp peaks from the typical 4f–4f transitions of Eu³⁺. Under excitation of UV, near-UV, or blue light, these phosphors showed strong red emission at 615 nm due to ⁵D₀–⁷F₂ transition of Eu³⁺. The incorporation of Mo⁶⁺ into LiEuW₂O₈:Bi³⁺ could induce red-shift of the charge-transfer broad band and a remarkable increase of photoluminescence. The highest red-emission intensity was observed with LiEu_0.80Mo₂O₈:0.20Bi³⁺. Compared with the commercial red-emitting phosphor, Y₂O₂S:Eu³⁺, the emission intensity of LiEu_0.80Mo₂O₈:0.20Bi³⁺ phosphor is much stronger than that of Y₂O₂S:Eu³⁺ and its chromaticity coordinates are closer to the standard values than that of the commercial phosphor. The optical properties of LiEu_0.80Mo₂O₈:0.20Bi³⁺ phosphor make it attractive for the application in white-light-emitting diodes (LEDs), in particular for near-UV InGaN-based white-LEDs.     

Superconducting Studies of Nd<Superscript>3+</Superscript>- and Dy<Superscript>3+</Superscript>-substituted GdBaSrCu<Subscript>3</Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> System

The compounds Gd_1−x Nd _x BaSrCu₃O_7−δ (where x=0, 0.1 and 0.2) and Gd_1−x Dy _x BaSrCu₃O _y (where x=0, 0.1 and 0.3) were synthesized using the solid state reaction technique. The tetragonal crystallization of the compounds was identified by powder X-ray diffraction. The microrange crystallite formation and the substitution elements present in the compounds were observed by SEM and EDX analyses. The suppression of superconducting transition temperature and the variation of magnetization parameters for the substitution of rare-earth magnetic elements Nd and Dy ions were observed by low-temperature electrical resistance and magnetization measurements.     

Nickel electrodeposition on copper substrate for cyclotron production of <Superscript>64</Superscript>Cu

Natural nickel electrodeposition on a copper substrate with a gold layer was studied with the aim of production of ⁶⁴Cu radionuclide. The electrodeposition experiments were carried out in acid plating baths. The operating parameters such as pH, temperature, and current density were optimized. The current efficiency was measured at different current densities. The optimum conditions of the nickel electrodeposition are as follows: 5.7 g 1⁻¹ nickel, pH 3–4, dc current density 85.54 mA cm⁻², and 55°C, with 97% current efficiency. SEM photomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath. A 46-μm high-quality layer was deposited on a gold layer of the copper substrate.     

Development and trials of a process for extraction recovery of <Superscript>99</Superscript>Mo for medical purposes from dissolved irradiated uranium targets

A process was developed for extraction recovery of ⁹⁹Mo from irradiated enriched uranium target. Dissolution of the uranium–aluminum composite in nitric acid in the presence of fluoride ions with the addition of mercury ions, which are subsequently separated by precipitation in the form of iodide, was suggested. Conditions were determined for joint recovery of uranium and molybdenum into the organic phase with 10–15% solutions of HDEHP in a paraffin diluent in the presence of equimolar amounts of TBP, and also for selective backwashing of Mo into a strongly acidic H₂O₂ solution with the backwash reflux. The efficiency of using a mixture of DTPA with methylamine carbonate for uranium backwashing and solvent regeneration was demonstrated. The recovery and separation process was successfully tested on simulated and real solutions in 20- and 19-step cascades of centrifugal contactors with the feed adjuster without Mo backwash reflux and with its reflux, respectively.     

Spindlelike Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> nanorod bundles: hydrothermal synthesis and photoluminescence properties

Uniform spindlelike Y(OH)₃ nanorod bundles were successfully prepared for the first time via a simple hydrothermal method at 200 °C for 12 h with the presence of Na₂H₂EDTA · 2H₂O (EDTA). Scanning electron microscope (SEM) images show that the obtained Y(OH)₃ spindlelike nanorod bundles have a length of about 11 μm and a diameter of about 2 μm in the middle part. The nanorod bundles are composed of numerous nanorods, and all these nanorods are orientationally aligned and grow uniformly along the bundles. The individual nanorod is with typical width of about 100 nm, thickness of about 40 nm, and length longer than 1 μm. The effects of reaction temperature, reaction time, and the concentration of NaOH and EDTA on the sizes and morphologies of the products have been investigated. The possible formation mechanism of the nanorod bundles was suggested. Spindlelike Y₂O₃ nanorod bundles were obtained after thermal treatment of the as-obtained Y(OH)₃ nanorod bundles at 700 °C for 4 h. X-ray powder diffraction (XRD) results demonstrate that the as-prepared Y(OH)₃ and Y₂O₃ are attributed to hexagonal phase and cubic phase, respectively. Eu³⁺ doped Y₂O₃ nanorod bundles were also prepared and their photoluminescence (PL) properties were investigated.