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Abstract  

The new method for the investigation of fast isotope exchange has been elaborated. It includes combination of the two procedures: (1) isotope exchange study without analytical separation of the components (electrolytical and diaphragm exchange methods); (2) method of constant velocity supply of the radioactively labelled component into the exchange system. The paper presents the derivation and analysis of correlations. The possibilities of the methods are discussed.

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Abstract  

A simple radioactive labeling technique is described which is based on a recoil injection of atoms of222Rn and its decay products from a226Ra source into thin surface layers of solids.

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Study of the diffusion of trace elements and radionuclides in soils

Capillary modification of the thin layer method. Diffusion of137Cs

Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Gosman and J. Blažíček

Abstract  

Thin layer method of measuring diffusion processes was modified to shorten time and to increase efficiency of experiments. For this purpose small and fine glass capillaries of 20 mm length and inner diameter of several millimeters were used as diffusion cells. The diffusion of trace amounts of137Cs, its dependence on soil moisture and interaction with the soil have been studied. Experimental technique. evaluation of records and the basic interpretation of the migration process are described.

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Abstract  

The method of constant velocity supply of the radioactive labelled component into the system was used to study the kinetics of the isotope exchange Tl(I)-hydroxyquinolate-Tl(III)-hydroxyquinolate in chloroform. The second order exchange reaction with a halftime less than 1 min was determined in the range of concentrations 0.2–2·10−3 M of both components.

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Abstract  

Alpha spectroscopy was used to study the mechanism of electrostatic collection of thoron daughters from the air. The results indicate that ThA atoms are primarily collected on negatively charged surfaces. Atoms of ThB produced by decay of ThA already attached to the collecting surface are injected by recoil into the surface layers of solids and are suitable for use in radiotracer experiments.

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Abstract  

Theoretical and experimental analysis of the diaphragm diffusion method for study of the state of trace elements in aqueous solutions is presented. It is shown that the method has substantial advantages over other diffusion methods and over conventional use of dialysis, particularly when nucleopore or other membranes with small internal surface area are employed. These advantages include rather short experimental time, not exceeding tens of minutes, lower adsorption losses and lower shift of equilibria among various forms of the trace element studied. A new method for the continuous measurement of and for the evaluation of diffusion is suggested, which enables calculation of the abundance of colloidal forms of the element. Verification of the method is carried out for a particular case using trace radiocerium.

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Abstract  

Theoretical and experimental analysis of the open-ended capillary diffusion method for study of the state of trace elements in aqueous solutions is presented. It is shown by theoretical considerations that the use of the discontinuous capillary method of diffusion and the evaluation of single measurements using the classical Anderson-Saddington equation yields incorrect diffusion coefficients if two or more forms of the trace element with significantly different diffusion characteristics are simultaneously present in the solution. A new method for the evaluation of diffusion is suggested, which enables calculation of the abundance of two different forms of a trace element. The method employs a continuous measurement of diffusion combined with computer analysis of the data obtained. Verification of the method is carried out for a particular case using trace radiocerium. The effect of adsorption on the diffusion measurement and interpretation is discussed.

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Abstract  

This paper presents the method of double labelling in the study of the kinetics of homogeneous isotope exchange reactions. This method was tested by the determination of the Sn(II)−Sn(IV) exchange rate in hydrochloric acid medium. The system was labelled by the tracer119mSn [initially in the Sn(IV) state]; when the isotope equilibrium was established, Sn(IV) was again labelled by tracer113Sn. The separation of Sn(II) and Sn(IV) in the given time of exchange was performed by the extraction of Sn(IV)-hydroxyquinolate into chloroform. The specific activities of the separated components were determined from the ratio of113Sn and119mSn activities. The exchange rate was calculated from the time dependence of specific activities. The advantage and possibilities of the method of double labelling in the study of isotope exchange are discussed.

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Abstract  

The possibility of preparation of237U by the238U(, n)237U reaction, realized by irradiation of UO3 on the microtron, has been verified. The relation between yields for (, n) and (, f) reaction was determined. The activated uranium was separated from fission products by extraction into diethyl ether.237U was used for the study of the kinetics of heterogeneous isotope exchange in the system aqueous solution of UO2(NO3)2 — ion exchanger Wofatit CA-20 in UO 2 2+ form. The experimental results were evaluated by a model based on particle diffusion with simultaneous isotope exchange between two uranium forms in the ion exchanger.

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