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  • Author or Editor: I. Ivanov x
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Abstract  

Prospects of the application of computers for the selection of optimum methods and for data-processing in activation analysis are discussed. Programs have been developed to select the irradiation source and the type of recording apparatus and to optimize time conditions. Various methods for handling gamma-radiation spectra are discussed. Complex utilization of the programs allows in many cases the elimination of the necessity of developing individual procedures, and the determination of the optimum method for a given element and given analysis parameter.

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Abstract  

Expanding application of activation analysis in industry resulted in exposure of features related to higher requirements to productivity, reliability, automation level, metrological support of analytical methods and equipment. Based on the application of neutron generators, radioisotope neutron sources, nuclear reactors, electron accelerators as activating radiation sources, high-productivity activation analytical systems used directly in analytical laboratories and plants were constructed. Level of development of the above works makes it possible to conclude that industrial activation analysis has formed as an independent trend of nuclear analytics and has considerable prospects.

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Abstract  

A cycle of the theoretical and experimental works has been carried out for determination of the activation analysis of mineral products using gamma-ray inelastic scattering reaction. The interference factor effect was studied. High-intensity waveguide linac LUE-8-5A type is used for the sample activation. The determination limit of elements using the isomeric states is 10−4 to 10−5 wt.% at the energy of the upper boundary of the bremsstrahlung (8 MeV). For the automatic search of the optimal analysis conditions an algorithm and computer program is developed. A geometry of the sample irradiation and measurement of its induced activity is proposed which ensures the uniform activation of a material of 500 g weight and effective measurement of the gamma-radiation of the induced activity with two NaI(Tl) crystals. The results of the above studies were used to construct a completely automatic inductrial facility for the photon-activation analysis of the geological materials. The output of the facility in the regime of the gold determination exceeds 300 000 analyses per year at the capability of analyzing up to 3000 samples per twenty four hours.

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The ovaries and the uterine as well as vaginal mucous membranes of 80-, 180- and 365-day-old intact female rats and females neonatally treated with a single dose of oestrogen and repeated doses of human chorionic gonadotropin (hCG) were studied. Numerous follicles, interstitial cells and corpora lutea (CL) were present on the ovary of intact females from 80 up to 365 days of age. The number of primary and secondary follicles decreased in the intact female rats between Day 180 and Day 365 of life. On the ovaries of 180- and 365-day-old female rats neonatally treated with oestrogen, interstitial glandular cells and cystic follicles predominated. No CL were present on these ovaries. The height of epithelial cells of the uterine and vaginal mucous membranes increased in intact female rats from 80 to 365 days of age, whereas in oestrogen-treated females the height of epithelium decreased. From 80 up to 365 days of age, the height of epithelial cells of uterine and vaginal mucous membranes of rats neonatally treated with repeated doses of hCG was similar to that in the corresponding control animals.

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The capital of Bulgaria, Sofia is a growing city with population around 1.22 million. The city is exposed to a high seismic risk since it is placed in the centre of Sofia seismic area. Over the centuries in the town of Sofia the macroseismic intensities have been larger than IX (MSK). A study of the site effects and the microzonation of a part of metropolitan Sofia, based on a  modelling of seismic ground motion along three cross sections are presented. Realistic synthetic strong motion waveforms have been computed for an expected scenario earthquake (M=7) applying a hybrid modelling method, based  on the modal summation technique and finite differences scheme. The site amplification is determined in terms of response spectra ratio (RSR). A set of time histories and quantities of earthquake engineering interest are supplied, that allow the definition of six zones characterized by specific response spectra. The results from this study constitute a “database” that describes the ground shaking of the urban area.  The synthetic velocigrams are employed to calculate the distribution of the horizontal strain factor Log10e using a simplified relation between particle velocity and velocity of shear waves in the surface layer. It is shown  that it is possible to estimate liquefaction susceptibility in terms of standard penetration tests (SPT), Nvalues and initial over burden stress. Using the data for maximum particle velocity and empirical relationships developed from the Northridge earthquake, 1994 the distributions of the expected pipe breaks and red-tagged buildings for Sofia city are shown.

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Authors: I. Ivanov, V. Sedov, A. Gulin, V. Shatkov and E. Shashukov

Abstract  

Diffusion coefficients of radionuclides237Np,239Pu and241Am in simulated alumina phosphate and alumina borosilicate glasses at temperatures lower than their transformation temperature were determined. Actinides are known to be the least mobile elements. In particular, the diffusion coefficients of actinides in alumina phosphate glasses at 673 K are about 10–18 m2·s–1, and in alumina borosilicate at 773 K about 10–19 m2·s–1. It is shown that crystallization of glasses leads to increasing237Np diffusion mobility. It is also shown that a rather small quantity of water absorbed by a crystallized alumina phosphate glass in tensifies low-temperature migration of237Np.

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Authors: I. Ivanov, V. Sedov, V. Shatkov and E. Shashukov

Abstract  

Diffusion coefficients of22Na,90Sr and134Cs in some aluminoborosilicate and silicophosphate glasses and ceramics have been determined by the integral residual radioactivity method. The temperature dependence of22Na diffusion coefficients has also been found.

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Authors: Yu. Bourmistenko, I. Ivanov, V. Sviridova and Yu. Feoktistov

Abstract  

The possibilities of using a computer to optimize the conditions of gamma-activation analysis are considered. Criteria of optimum conditions are formulated. The optimization program is constructed of the following operations being automatically performed: (1) determination of a list of isotopes and their gamma-lines formed during the interaction between the activating bremsstrahlung and the substance whose elemental composition elements to be analyzed plus matrix is preliminarily given; (2) optimization of the analysis time regimes and the value of the maximum energy of the activating bremsstrahlung; (3) choice of a gamma-line of the isotope of an element to be analyzed by which the quantitative determination of this element is expedient. For these purposes a catalogue of nuclear-physical constants (half-lives and energies which was compiled from published data tables of gamma-line outputs obtained experimentally under standardized conditions for different values of the maximum energy of the bremsstrahlung as well as mathematical models of the monoenergetic gamma-ray spectra) has been used.

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Authors: B. Anisimov, Yu. Bourmistenko, I. Ivanov and V. Philippov

Abstract  

A mathematical model is suggested for the approximation of the monoenergetic gamma-ray spectra obtained by a Ge(Li) detector. Some features of the instrumentation monoline spectra in the energy range upto 2 MeV are considered in detail. Computer program “APPROXIMATSIYA” is described. The program allows to determine the parameters of the mathematical model with the purpose to construct a making up standard spectrum library. The results of the monoline spectrum processing are discussed.

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Résumé  

On a déterminé la composition élémentaire d'échantillons de régolite lunaire obtenus par Luna 16 dans la mer d'abondance par méthode radioactive à l'aide d'un générateur de neutrons ainsi qu'un spectromètre γ à scintillations et détecteur Ge(Li).

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