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Spallation produced radiolanthanoides via tantalum

Coprecipitation with fluorides and separation in short columns with cation exchange resin

Journal of Radioanalytical and Nuclear Chemistry
Authors:
V. Khalkin
and
N. Lebedev

Abstract  

Nuclear reactions of tantalum spallation by high energy protons are an effective way to get neutron deficient radiolanthanoides of the yttrium subgroup of rare-earth elements. Lanthanoides were separated from tantalum dissolved in HF-HNO3 by coprecipitation with LaF3 absorbed in a cation exchange resin. This excluded completely their loss at the stage of preparation for chromatographic separation. The combined sample of lanthanoides was separated to individual elements in short columns 70×3 mm Aminex A-5 13±2 m by a buffer solution of alpha-hydroxyisobutyric acid with pH 4.5. The target treatment and chromatographic separation lasted for about an hour. The chemical yield of elements was about 90%, contamination with neighbouring lanthanoides being notmore than 1%. The technique was developed with a glance to using it behind a biological shield with the help of remote-control devices.

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Abstract  

The mobility of oxidized astatine in solutions H(Na)ClO4 (=0.4 M) – 1·10–4M K2Cr2O7 has been measured at 25°C in the interval 0.63pH1.68. Under these conditions astatine migrates to the cathode only. The speed of the migration depends upon the concentration of hydrogen ions in solution: pH 1.68 Uc = 1.17 · 10-4 cm2 V-1 s-1 pH 0.63 Uc = 2.67 · 10-4 cm2 V-1 s-1 The effect agrees with the opinion that the singly charged cation of astatine formed in acidic solutions is a strong aquacomplex [(H2O)xAt]+ (x=1–2) (protonated hypoastatic acid). Deprotonation constant of this cation is Kdp=0.032±0.005. Specific properties of the astatine cation are given. They can be explained, probably, through the peculiarities of its structure.

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Abstract  

Dependence upon pH of Ac and Th distribution coefficients between the cation exchange resin and buffer citrate solutions had been investigated; the optimal conditions are suggested for effective separation of the elements in this system. These results are in successful accordance with such conditions calculated on the basement of Ac and Th citrate complex formation constants.The generator method for225 Ac periodical separation from229 Th samples is developed.229 Th storage in solution between separations excludes the contamination of actinium final solution with radiolysis products and provides 100-% yield of this isotope and its high radiochemical purity. The parent nuclide loss after continuous use of the generator does not take place.

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Abstract  

The nuclear reactions of (p, xn)-type, Ep=100–120 MeV, on Gd and Nd have been used to produce highly radioactive preparations of Tb and Pm enriched with neutron-deficient isotopes. Under comparable conditions the yields of practically all isotopes are considerably higher than in Tb and Gd spallation reactions at Ep=660 MeV. The radioactivity of screened154Tb and156Tb isotopes has been increased more than 40 times. Tb and Pm were separated from gram amounts of the target-elements by the extraction chromatography technique with undiluted di-(2-ethylhexyl) phosphoric acid as stationary phase. The radiochemical method developed was also applied to separate the radiochemically pure preparation of161Tb from Gd oxide irradiated with thermal neutrons.

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Abstract  

A new variant of a technique for determining ion mobilities by means of horizontal zone electrophoresis in free solutions is developed. Setup circuit is presented. Some details of experiment and results of measuring limiting mobilities of131I-and160Tb3+ are given. On these examples the reproductibility was checked.

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Abstract  

The hydrolytic behavior of trace quantities of tetra- and pentavalent vanadium has been studied by the zone electrophoresis method in a wide pH range (2–12). For the first time, the mobilities of all hydrolytic vanadium forms were determined in dilute nitric acid solutions of ionic strength 0.1M at 298 K.

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Abstract  

The dissociation energy of C–At bond /DC–At/ in a number of astatobenzene derivatives has been determined by pyrolytic method. The values of DC–At for the astatoaromatic compounds investigated have been found to be independent of the substituents and their relative position in the astatoaromatic system.

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Abstract  

Electrophilic aromatic astatination of equimolar mixtures of benzene and its derivatives has been studied in acid homogeneous medium. It has been quantitatively estimated, on the basis of the Hammett equation, how the properties of substitutients influence the yield of reaction products.

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Abstract  

Carrier-free astatotyrosine has been synthesized using an electrophilic reaction in acidic media. Temperature of 150–160°C and reaction time of 20–30 min were chosen as optimal conditions for the synthesis of astatotyrosine. Under the selected conditions the yield was about 90%.

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Electromigration of carrier-free radionuclides

IV. Oxalate and tartrate complexes of La(III) in aqueous solution

Journal of Radioanalytical and Nuclear Chemistry
Authors:
F. Rösch
,
R. Herrmann
,
Tran Hung
,
M. Milanov
, and
V. Khalkin

Abstract  

Dependences of La(III) overall ion mobilities
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$u_{La^{3 + } }^{\mu = 0}$$ \end{document}
=+6.9(1)·10–4 cm2·s–1·V–1 for pure water at 298.1 K.
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