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  • Author or Editor: N. Dogadkin x
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Abstract  

A generator system, consisting of two anion- and one cation-exchange columns for production of medical α-radionuclides 225Ac and 213Bi, has been developed. The first anion-exchange column was used for periodical separation of 225Ac from Th with 8 M HNO3, while the second anion-exchange column was employed for purification of 225Ac from Ra and inactive impurities in mixed HNO3/CH3OH media. From anion-exchange column 225Ac was stripped with 0.1–0.2 M HNO3 and loaded directly onto cation-exchange column, used as a generator for repeated isolation of 213Bi. The cation exchange behavior of Bi and other radionuclides of the interest were studied in diluted HCl, HBr and DTPA solutions used as eluents. As result, a simple and effective method for the production and purification of 225Ac and 213Bi suitable for biomedical studies was elaborated.

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Abstract  

Beta autoradiography and progressive acid leaching have been used to investigate the distribution of Ir in silicates in the presence of carbon phases as well as without these phases. Determinations of Ir by neutron activation analysis gave results for the Ir content of basaltic glasses after experiments at 1 bar of 82 ng·g−1 (NNO buffer), 30 ng·g−1 (CCO equilibrium) and 37 ng·g−1 (IW buffer). Iridium solubility in basaltic melt in the presence of graphite and (CO, CO2) fluid increased from 1.6 μg·g−1 at 0.5 kbar to 6.2 μg·g−1 at 2 kbar. These data give Ir partition coefficients between solid metal and liquid silicate in the presence of carbon phases. Discrete (Ir, Fe) rich phases were discovered in the basaltic melt at 3 kbar and 1250°C preventing the determination of solubility data. Our results provide clear evidence that the iridium solubility in a basaltic melt in the presence of carbon is higher than the solubility of iridium in melts without carbon.

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Abstract  

A method has been developed for the activation analysis of boron and cadmium, taking into account neutron absorption of the sample. The concept of the screening coefficient, expressing the self-screening of the matrix on the contamination is introduced. A formula is proposed for calculation of the screening coefficient, based on the boron or cadmium ratios for the contaminating elements being determined. Good agreement between experimental and calculated values was obtained.

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Abstract  

A semiempirical method of allowing for the effect of impurity element screening in samples of irregular geometry, absorbing thermal and resonance neutrons, is suggested. The accuracy of this method was evaluated for cobalt, silver, indium, iridium, gold and mercury and experimentally checked for silver and indium samples.

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Abstract  

A calculation method of self-shielding coefficients of interesting elements in samples of any forms is given for the neutron activation analysis of cadmium and its compounds. The determination of ten elements in cadmium telluride using radiochemical separation and γ spectrometry is described.

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Abstract  

It has been demonstrated that pixel-by pixel processing of series of autoradiography images for revealing the dynamics of decay of the induced radionuclides is an efficient approach for mapping of radionuclides in the sample in activation autoradiography. Concepts of virtual scanner and corresponding software for linearization of dependence of optical density on scanner response (luminosity) have been introduced. The concept provides unification of the subsequent processing of autoradiograms, irrespective of the method as to how the digital image has been obtained. Algorithms and the software for estimation of decay parameters of a radionuclide mixture for each pixel using a series of coaxially positioned images have been developed. The software is able generate a set of the derivative meta-images allowing a conclusion to be made about the presence of the inclusions in question. To increase the reliability of radionuclide mapping it is suggested to use analysis of distribution of half-life values estimated for pixels of image zone(s) pointed by a special mask.

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Abstract  

The activating field of microtron bremsstrahlung is characterized by sharp recession of intensity in lateral and longitudinal directions. Therefore, the irradiation of several samples simultaneously results in their different activation which is a source of systematic error. Evaluation of correction coefficients needed for quantitative analysis by measurement of thin copper disks placed between the samples does not result in acceptable data. For these purposes a method for 3D-activating field monitoring and Monte-Carlo simulation for computation of the needed correction coefficients has been developed. The monitor represents the copper foil wrapped round the sample assembly. The autoradiogram of the irradiated monitor is used for characterization of the activating field. The Monte-Carlo simulation model involves both the field characteristics and the results obtained while making single training analysis.

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Abstract  

A simple and effective method has been developed for the continuous production of the short-lived isotope Pb as a homolog of element 114 on the principle of a radionuclide generator. The method is based on the initial sorption of 227Ac or 223Ra on a small cation-exchange column, with subsequent “milking” of 211Pb (36.1 m) by a mixture of HCl/CH3OH. The optimum conditions for the repeated separation of 211Pb from radionuclides strongly sorbed by the cation-exchanger (Ac, Th, Ra, Pu, TPE) have been determined. Possibilities of using the 211Pb generator for test experiments on the solution chemistry of element 114 have been shown. Advantages of aqueous alcohol HCl solutions for the isolation of 211Pb (element 114) are discussed.

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Abstract  

A radiochemical procedure for determination of ultra low concentrations of phosphorus in germanium has been developed. The method involves application of multicells autoclaves for matrix distillation and extraction chromatography with dioctyltin diacetate for final phosphorus purification. The detection limit is 40 ppt for a 1-g sample.

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Abstract  

Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is complicated by the short half-life of165Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating 10 mg of Y2O3 with a flux of 1.2·1013 n·cm−2·sec−1 for 5 min. was 1·10−7%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y2O3 for 20 hours with the same flux, were 2·10−7%, 1·10−8% and 5·10−6%, respectively.

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