Coprecipitation of microamounts of radionuclides on chitosans of various molecular weights in solutions

Coprecipitation of ²³³U, ²³⁹Pu, ²⁴¹Am, ¹⁵²Eu, ⁹⁰Sr, ⁹⁰Y, and ⁶⁰Co on chitosans of various molecular weights (MW) was studied. Low-molecular-weight chitosan (LMWC) with MW of 5 kDa (5 × 10³ g mol⁻¹) proved to be a more effective coprecipitant than high-molecular-weight chitosan (HMWC) with MW of 700 kDa (7 × 10⁵ g mol⁻¹). With HMWC, the degree of coprecipitation (α) was 80% for ¹⁵²Eu and ⁹⁰Y, 99% for ²³³U and ²⁴¹Am, and 85% for ²³⁹Pu. For ⁶⁰Co, α monotonically increased with an increase in the chitosan concentration in solution and reached 40% at [HMWC] = 5 g l⁻¹. For ⁹⁰Sr, α did not exceed 3% in the entire examined range of chitosan concentrations. With LMWC, the α values for An, ¹⁵²Eu, and ⁹⁰Y differed insignificantly (92–99%). For ⁶⁰Co and ⁹⁰Sr, α increased to 40% in the range of chitosan concentrations from 0 to 1 g l⁻¹. The presence of inorganic salts in solution considerably decreases α of UO₂²⁺ with chitosans but does not noticeably affect the behavior of Am, Pu, and Eu. The effect of salts on the efficiency of ²³³UO^2/2+ coprecipitation on HMWC decreases in the order Na₂SO₄ > NaCl > Na₂CO₃ > NaNO₃ > Na₃PO₄. Based on the results obtained, a procedure suitable for expedition conditions was developed for preconcentration of Pu from seawater on chitosan, with simultaneous separation of Pu from U, for radioecological monitoring of natural waters. The specific activity of Pu in samples of near-bottom seawater of gulfs of the Novaya Zemlya archipelago was (150–170) ± 20 mBq m⁻³. The results are well consistent with the published data.     

Excitation of doublet states of yttrium atom by electron impact

The excitation of odd doublet states of yttrium atom by slow monoenergetic electrons is investigated. The obtained experimental values of the excitation cross sections of spectral lines of YI are used for the calculation of the excitation cross sections of energy levels. The levels pertaining to the termsx ² P ⁰,y ² D ⁰, andy ² F ⁰ have the largest total excitation cross sections. The contribution by cascade population is about 20% for the levelsz ² D ⁰ and about 3.5% for the levelsz ² F ⁰.     

Desorption of 90Sr and 137Cs from Flood Plain Deposits of the Sozh River and Rocks of the Adjacent Catchment Areas

Desorption of ⁹⁰Sr and ¹³⁷Cs from flood plain warps, meadow sod, humus-containing sandy loam, peat, clays, limonite, meadow marl, and friable rocks of the adjacent catchment areas (moraine clay, loam, sandy loam) was studied. ¹³⁷Cs is sorbed the most strongly on clays by the mechanism of isomorphic ion-exchange incorporation into the crystal lattice of montmorillonite-type minerals. ¹³⁷Cs is also tightly fixed on buried and peaty soils due to association with the poorly mobile species of humic acids and humin. The strong fixation of ⁹⁰Sr on amorphous iron hydroxides is caused by its association with poorly soluble ferrite-type minerals. Sorption of ⁹⁰Sr on peaty soils can be attributed to their association with aluminum and iron-containing organomineral complexes. ¹³⁷Cs sorbed on flood plain warps, sandy loams, and loams exhibits increased mobility and is leached with all the tested desorbing solutions. These deposits apparently contribute maximally to the redistribution of radiocesium over flood plain and the adjacent catchment areas. The desorption efficiency of cations of the desorbing solutions decreases in the order Cs⁺ > K⁺ > Fe^{3 +} > NH₄ ⁺ > Ca^{2 +} > H⁺ for radiocesium and Fe^{3 +} > Sr^{2 +} > K⁺ > H⁺ > Ca^{2 +} > NH₄ ⁺ for radiostrontium.     

Influence of Ce on the luminescence properties of Er/Yb:YVO4 crystals

YVO₄ single crystals doped with Ce³⁺, Er³⁺ and Yb³⁺ ions were grown by the Czochralsski technology. The luminescence properties of Er³⁺/Yb³⁺:YVO₄ single crystals with different concentration of Ce³⁺ were studied, and the energy transfer mechanism between Er³⁺, Yb³⁺ and Ce³⁺ was discussed based on their energy level properties. The branching ratios of the ⁴I_11/2 → ⁴I_13/2 transition in different samples were calculated. The results indicate that codopants of Ce³⁺ greatly enhance the population rate of the ⁴I_13/2 level due to the fast resonant energy transfer between Er³⁺ and Ce³⁺, i.e., ⁴I_11/2(Er³⁺) + ²F_7/2(Ce³⁺) → ⁴I_13/2(Er³⁺) + ²F_5/2(Ce³⁺).     

Behavior of Trace Amounts of Cd and Zn in Sorption and Coprecipitation in Tetrahydrofuran Solutions

Sorption of trace amounts of ¹⁰⁹Cd and ⁶⁵Zn on zeolites NaX and NaA in the presence of divalent lanthanides Ln²⁺ (Ln = Tm, Dy, Nd) from tetrahydrofuran (THF) solutions is studied. In contrast to ¹³⁷Cs⁺ and similar to ⁸⁵Sr²⁺, trace amounts of ¹⁰⁹Cd and ⁶⁵Zn are not practically sorbed on zeolites (about 99% of these radionuclides remains in the solution). The distribution coefficients K _d of ¹⁰⁹Cd and ⁶⁵Zn are ∼0.3 and ∼0.4 ml g⁻¹, respectively. In THF solutions, Tm²⁺ is oxidized to Tm³⁺, and TmI₃ ⋅ 3THF is precipitated. Study of cocrystallization of trace amounts of ¹⁰⁹Cd and ⁶⁵Zn and also of ⁸⁵Sr with this precipitate from THF solutions containing Tm²⁺ revealed that, in contrast to ⁸⁵Sr²⁺, ¹⁰⁹Cd and ⁶⁵Zn traces cocrystallize with the solid solvate phase. The cocrystallization coefficients D of ¹⁰⁹Cd and ⁶⁵Zn increase with increasing Tm³⁺/Tm²⁺ ratio in the solution. The mechanism suggested is that, in the presence of Tm²⁺, ¹⁰⁹Cd²⁺ and ⁶⁵Zn²⁺ are reduced to single-charged cations M⁺, which then rapidly react with the double-charged cations M²⁺ with the formation of dimers M ₂ ³⁺ (M = Cd, Zn).__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 261–264.Original Russian Text Copyright © 2005 by Veleshko, Kulyukhin.     

Production of 2-[18F]Fluoro-2-deoxy-D-glucose at the Laboratory of Radiochemistry, University of Helsinki

Production 2-[^{1 8}F]fluoro-2-deoxy-D-glucose ([^{1 8}F]FDG) was started at the Laboratory of Radiochemistry in 1998 when a cyclotron, specially designed for the production of short-lived positron emitters, was bought to the laboratory. The radiosynthesis of [^{1 8}F]FDG is based on aminopolyether-mediated nucleophilic fluorination. [^{1 8}F]Fluoride is produced by the ^{1 8}O(p,n)^{1 8}F nuclear reaction. [^{1 8}F]FDG is synthesised with an automated device. The radiochemical yield of the synthesis is 50% (by the end of bombardment). Sterile and isotonic [^{1 8}F]FDG solution is produced within 55 min. [^{1 8}F]FDG is delivered for patient use by the medical company MAP Medical Technologies.     

Kinetics of Redox Reactions of Np and Pu Ions with Hydrazine Derivatives: XVI. Reaction of Np(V) with Phenylhydrazine

The rate of Np(V) reduction with phenylhydrazine in a perchloric acid solution is described by the equation d[Np(IV)/dt = k ₁[Np(V)][C₆H₅N₂H₄ ⁺] + k ₃[Np(V)][C₆H₅N₂H₄ ⁺][H⁺]² + k ₂[Np(V)][Np(IV)], where k ₁ = 1.27 × 10^{- 3}, 2.81 × 10^{- 3}, and 5.86 × 10^{- 3} l mol^{- 1}min^{- 1}; k ₃ = 2.32 × 10^{- 3}, 1.21 × 10^{- 2}, and 5.75 × 10^{- 2} l³ mol^{- 3} min^{- 1}; and k ₂ = 1.1, 8.3, and 50 l mol^{- 1} min^{- 1} at the ionic strength = 4 and 40, 60, and 80°C, respectively. The activation energies of three reaction pathways are E ₁ = 35±7, E ₃ = 74±17, and E ₂ = 88±1 kJ mol^{- 1}. The reaction is self-accelerated owing to formation of the reactive intermediate, hydroquinone. Its concentration in the reaction mixture is proportional to the concentration of the final product, Np(IV) ion. Probable slow stages of two main and autocatalytic pathways of the reaction are discussed.     

Effect of Ce(Eu) codoping on the spectroscopic properties of Er in bismuth-germanate glass

In order to improve the transition rate from the ⁴I_11/2 level to the 1.53 μm fluorescence emitting ⁴I_13/2 level of Er³⁺, the Ce³⁺ and Eu³⁺ ions were respectively introduced into the Er³⁺ doped bismuth-germanate glass with a composition of Bi₂O₃–GeO₂–Ga₂O₃–Na₂O. The energy transfer mechanisms between Er³⁺ and the codopants were discussed based on their energy level diagrams. Though Ce³⁺ was less effective than Eu³⁺ on the decrease of the ⁴I_11/2 level lifetime, it hardly influenced the lifetime value of ⁴I_13/2 level. Both the ⁴I_11/2 and ⁴I_13/2 levels were depleted severely at the same time with the codoping of Eu³⁺. As a result, Er³⁺/Ce³⁺ codoping improved the 1.53 μm fluorescence emission intensity, while Er³⁺/Eu³⁺ codoping had a deleterious effect on it. The results indicate that the Er³⁺/Ce³⁺ is a preferable codoped scheme for bismuth-germanate glass with low phonon energy to obtain an efficient broadband EDFA pumped at 980 nm.     

Some characteristics of electric explosion of zinc wires

Some physical characteristics necessary for calculating the circuit of and selecting the optimum conditions for the electric explosion of zinc wires have been experimentally determined, including the specific action of zinc h _b = (0.70 ± 0.15) × 10⁵ A² s/mm⁴ (for maximum current densities 2.5 × 10⁵ A/mm² < j _M < 4.5 × 10⁵ A/mm²) and the critical length of exploding wire λ_cr = 1.8 × 10³ (ɛν × 10⁻⁶)^0.56.     

Sorption of long-lived radionuclides onto main types of rocks of the Novaya Zemlya Archipelago

The ability of black carbonaceous siltstones and silt sandstones, lime sandstones, gray limestones, carbon–silicon carbonate schists with pyrite, and other rocks that most widely occur on the Novaya Zemlya Archipelago to sorb ¹³⁷Cs, ⁹⁰Sr, ^239+240Pu, and ²⁴¹Am was studied. The distribution coefficients K _d (cm³ g^–1) are as follows: for ^239+240Pu, 2.7 × 10³–7.7 × 10³; for 241Am, 2.5 × 10³–1.8 × 10⁴; and for ¹³⁷Cs, 1.1 × 10²–2.0 × 10³. Strontium-85(90) it not noticeably sorbed (within the measurement uncertainty) by any of the rocks studied. ^239+240Pu, ²⁴¹Am, and ¹³⁷Cs are strongly sorbed onto the rocks studied and are not noticeably desorbed from them with distilled water. The data obtained are required for predicting the migration of long-lived radionuclides generated by nuclear explosion with surface waters from test sites on the Novaya Zemlya Archipelago.     

船用结构钢合金成分优化及耐微生物腐蚀性能研究

为了优化船用结构钢合金元素,提高其耐微生物腐蚀性能,研究了船舶用结构钢冶炼中常见的10种重金属元素对海洋微生物生长的抑制能力,探讨了金属离子毒性与细菌胞外分泌物(EPS)选择吸附的关系,并采用电化学、倒置荧光显微镜和原子力显微镜分析了经过合金元素优化后的试样的耐微生物腐蚀性能。实验结果表明,金属离子抑制毒性与 EPS 的选择吸附有密切关系,EPS 对这些金属离子的吸附能力越强,该金属离子对细菌的毒性就越大;对于革兰氏阴性菌而言,各重金属离子的毒性大小为 Cu2+> Zn2+>Ni2+>Pb2+>Cr3+>V5+>Co2+>Mo6+>Mn2+> Al3+,对于革兰氏阳性菌而言,各重金属离子的毒性大小为 Ni2+> Zn2+> Cu2+> Co2+> Cr3+>Pb2+>V5+> Mn2+> Mo6+> Al3+;优化 Ni、Cu、Cr 三种合金元素在试样中的含量,在一定程度上均可以加强试样在无菌介质和有菌介质中的耐腐蚀性能。同时提高合金元素 Ni、Cu 和 Cr 在钢材中的含量对于提高材料的耐微生物附着腐蚀性能最为显著。     

Absorption Bands of Carbon Dioxide From 5.3 to 4.6 Microns

Measurements have been made of the frequencies of the infrared absorption lines of CO₂ in the region from 1850 cm⁻¹ to 2150 cm⁻¹. Observations were made at various pressures and pathlengths up to a maximum of 72 meter-atmospheres. Vibration-rotation constants were obtained characterizing the transitions 11^1c0–000, 11^1d0–000, 03^1c0–000, 03^1d0–000, 200–01^1c0, I2^2c0–01^1c0, 12^2d0–01^1d0 for C¹²O₂. The 11^1c0–000 band due to the C¹³O₂ molecule was also measured.     

Fabrication of electrically conductive membrane electrode of gelatin-tin (IV) phosphate nanocomposite for the detection of cobalt (II) ions

Gelatin-tin (IV) phosphate nanocomposite (GT/TPNC) ion exchanger was synthesized by mixing gelatin gel into the precipitates of tin (IV) phosphate using sol–gel method. GT/TPNC was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ion exchange capacity of GT/TPNC was reported to be1.44?meq/g. The material was found monofunctional as indicated from pH titration curves. The distribution coefficient of different metal ions such as Zn²⁺ (42.10), Cd²⁺ (37.93), Mg²⁺ (33.33), Cu²⁺ (33.21), Al³⁺ (14.28), Pb²⁺ (6.06), Ni²⁺ (12.50) and Co²⁺ (50.0) was studied using GT/TPNC ion exchanger. The distribution studies confirmed the selectivity of GT/TPNC for Co (II). The photocatalytical degradation of MB was found to be 78% within 5 h of solar illumination using GT/TPNC. Some binary separations such as Co²⁺–Pb²⁺, Cd²⁺–Ni²⁺, Co²⁺–Mg²⁺, Mg²⁺–Zn²⁺, Pb²⁺–Zn²⁺, Cu²⁺–Al³⁺, Al³⁺–Cd²⁺, Ni²⁺–Cu²⁺ were attempted using GT/TPNC ion exchanger. GT/TPNC was explored for the fabrication of ion-sensitive membrane electrode for the determination of Co (II) in the water system. The membrane electrode was found mechanically more stable with quick response time (30?s) and a wide pH working range (4.0–7.0).     

Precision Measurement of the 2

Abstract

The 4f¹³ 6s^{2 2}F_7/2–4f¹⁴ 5d ²D_5/2 3·43 μm infrared transition in ¹⁷²Yb⁺ has been driven for the first time and measured to be 87 360 087(4) MHz. The frequency was determined by probing a cloud of ¹⁷²Yb⁺ ions held in a radiofrequency trap in the presence of helium buffer gas. The infrared radiation was generated by difference frequency mixing in LiNbO₃. The frequency measurement is part of a programme to locate the 4f¹⁴ 6s ²S_1/2–4f¹³ 6s^{2 2}F_7/2 467 nm ultra-narrow transition in laser-cooled Yb⁺.     

Use of Purbe diagrams in prediction of optimum conditions of separation and determination of halogens in natural objects using ionometry

Directional oxidation in the solution of X ⁻ ion being determined down to elementary halogen X ₂ and separation of it using gas extraction is promising for the separation of halogenide ions (Cl⁻, Br⁻, I⁻). The coinciding Purbe diagrams for redox systems of halogens X ⁻/X ₂ and most widely used oxidizers, namely, MnO₄⁻/MnO₂, MnO₄⁻/Mn²⁺, PbO₂/Pb²⁺, Cr₂O₇⁻/Cr³⁺, HNO₂/NO, were fragmentarily plotted. The predicted working pH intervals of the medium for directional quantitative oxidation of the given halogenide ion by a particular oxidizer were ascertained graphically using the diagrams. The possible schemes for the independent ionometric determination of Cl⁻, Br⁻ and I⁻ ions were proposed.     

Cocrystallization of Radioiodine Compounds from the Gas Phase

The study of the behavior of ¹³⁷Cs¹³¹I in the presence of MCl (M = NH₄ ⁺, K⁺, Ag⁺, and Cu⁺) in the water vapor-gas phase showed that CsI aerosols are localized in the MCl matrix owing to both agglomeration cocrystallization [¹³⁷Cs¹³¹I-MCl systems (M = K⁺, Ag⁺, NH₄ ⁺)] and agglomeration capture [¹³⁷Cs¹³¹I-CuCl system]. The main advantage of the first process is formation of crystalline globules encapsulating radioiodine in their bulk, which prevents transformation of radioiodine into elemental iodine and methyl iodide.     

Leaching of radionuclides from products of underground nuclear explosions in granite: Experiments with radioactive samples of melted rock from explosion cavities on Semipalatinsk test site

Leaching of ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu from products of underground nuclear explosions in tunnels 504R, 148/5, and 190 of the Semipalatinsk test site was studied. Samples were taken from central zones of the explosions. Sample characteristics are presented. Leaching experiments were performed in the batch and dynamic modes. The degrees and rates of ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu leaching with granite aqueous extract were determined. The leach rates determined in batch experiments are in the following ranges: ⁹⁰Sr 2.3 × 10^?6?1.6 × 10^?4, ¹³⁷Cs 5.0 × 10^?6?2.5 × 10^?4, and ^239+240Pu 5.6 × 10^?7?2.1 × 10^?4 g cm^?2 day^?1, and those determined in dynamic experiments are in the following ranges: ⁹⁰Sr 9.2 × 10^?10?10^?8, ¹³⁷Cs 1.0 × 10^?9?1.6 × 10^?7, and ^239+240Pu 1.3 × 10^?11?2.5 × 10^?11 g cm^?2 day^?1. The values obtained are close to those reported in the literature for vitrified radioactive wastes.     

Features of Electrolysis of Nitric Acid Solutions of Silver: I. Behavior of Ag(II) in HNO3 Solutions

The current efficiency of Ag(II) formation in the course of electrochemical oxidative dissolution of PuO₂ was determined. It approaches 72% at the anodic potentials from 1.9 to 2.1 V (vs. SHE) and the anodic current densities of 0.006-0.013 A cm^{- 2}. The behavior of Ag(II) in 4 M HNO₃ at 8, 25, and 40°C was studied. The reaction of Ag(II) with water can be described by the equation d[Ag(II)]/dt = kapp[Ag(II)] ⁿ , where n 2 at 8-25°C and 2-1.5 at 39-41°C. The apparent rate constants of the reaction are 1.5 and 3.8 l mol^{- 1} min^{- 1} at 8.5°C and 25°C, respectively. At 39-41°C, the reaction order with respect to Ag(II) ranges from 2 to 1.5, and the rate constant is about 1.2 l^{1 / 2} mol^{- 1 / 2} min^{- 1}.     

Photon-avalanche upconversion of Ho in NaYF4 and enhancement of violet, blue and green emissions induced by sensitization of Tm

Ho³⁺ singly doped and Ho³⁺/Tm³⁺ co-doped hexagonal NaYF₄ powders have been synthesized by a solid-state reaction method. Under excitation of 671 nm diode laser, upconverted blue, green and red emission bands are observed in Ho³⁺ singly doped sample. Temporal evolution and excitation power dependent behavior for the green emission are explored, indicating that a photon-avalanche mechanism is responsible for the upconversion processes in Ho³⁺ singly doped hexagonal NaYF₄ sample. With the introduction of Tm³⁺, the intensities of both blue and green emissions of Ho³⁺ are efficiently enhanced, which are attributed to two energy transfer processes from Tm³⁺ to Ho³⁺, i.e., ³F₄ (Tm³⁺) + ⁵I₈(Ho³⁺) → ³H₆ (Tm³⁺) + ⁵I₇(Ho³⁺) and ¹G₄ (Tm³⁺) + ⁵I₈(Ho³⁺) → ³H₆ (Tm³⁺) + ⁵F₃(Ho³⁺). The result offers a new sensitization approach to enhance the upconversion efficiency of Ho³⁺ under 671 nm excitation.     

Multiplicity of europium centers in doped stoichiometric crystals of lithium niobate

The optical spectra of europium-doped stoichiometric lithium niobate (LiNbO₃:Eu³⁺) crystals have been studied using combined excitation-luminescence spectroscopy in the range of ⁵D₀ → ⁷F₁, ⁷F₀ optical transitions. Analysis of the results shows that Eu³⁺ ions can occupy 14 energetically nonequivalent positions in the LiNbO₃ crystal lattice. This multiplicity of impurity centers is related to possible variants of the incorporation of Eu³⁺ ions into the LiNbO₃ crystal lattice and the compensation of excess charge. Energy positions of the ⁵D₀ level and the lowest sublevel of the ⁷F₁ Stark multiplet are determined for Eu³⁺ centers of all 14 types.