[en] A study is made of the propagation of electromagnetic waves in an infinite fine-stratified periodic structure composed of alternating layers of two different semiconductors. Such a periodic structure has four characteristic frequencies: two plasma frequencies of the layers and two hybrid frequencies, which are determined by the parameters of the layers. These frequencies govern the dispersion properties of the eigenwaves of the semiconductor structure. The effect of the dissipative processes on the wave dispersion is considered, and the dependence of the minimum phase velocity on the thickness of the layers and on the collision frequency between charge carriers within them is determined

[en] Two method for evaluating the exchange coefficient for the ⁹⁰Sr and ¹³⁷Cs distribution in the soil-water system: the ¹³⁷Cs effective selectivity and selective sorption are proposed. The principles of soil and sediments classification in dependence on the selectivity effective coefficient are proposed. The evaluation of the ⁹⁰ distribution coefficient through the first method may be accomplished by the medium known sorption properties with the error not exceeding 50%; and only the order of the distribution coefficient value may be achieved for ¹³⁷ Cs. The decrease in the uncertainly of the ¹³⁷Cs distribution forecasting may be achieved through determination of its selective sorption characteristics: the capacity of the selective sorption centers and/or the exchange potential of cesium binding

[en] The method for evaluating the ¹³⁷Cs and ⁹⁰Sr distribution coefficient in soils and sediments, based on the forecast of their speciation and estimation of the distribution exchange coefficient, is proposed. It is shown, that fixation of radionuclides is a reversible process. The model for the ¹³⁷Cs and ⁹⁰Sr chemical forms transformation including leaching from fuel particles, fixation and remobilization is suggested. It is shown, that the first order kinetic model satisfactorily describes the ⁹⁰Sr also ¹³⁷Cs forms for the one month period. Application of the diffusion fixation model is more preferable for longer periods of time in the ¹³⁷Cs case. The key parameters for various types of soil are recommended. The data on contamination of the 30 km zone of the Chernobyl NPP are used as examples

[en] Short communication

[en] Ammonium acetate concentration effect on the ¹³⁷Cs desorption level from bottom sediments of the Svyatoe and Kozhanovskoe fresh water lakes located in the Bryansk region was studied. For the purpose of elucidation of real part of the ¹³⁷Cs exchange form method based on using diluted ammonium acetate (10^-3 M) as extractant from which ¹³⁷Cs is absorbed by special sorbent (infinite dilution method) is proposed. It is noted that the same ¹³⁷Cs desorption degree at different concentration of displacing solution testifies that the part of exchange form is independent on the ammonium acetate concentration provided that the ammonium acetate amount is held constant in calculation on unit of mass of sorbent

[en] Short communication

[en] A diffusional model of radiocaesium fixation in soils and bottom sediments was developed. According to this model fixation is a result of radiocaesium cations diffusing into the surface layer of soil or sediment particles. Good agreement between predicted and experimental time dependences of ¹³⁷Cs fixation rate in soils indicates that the proposed model seems adequately to reflect the actual mechanism of radiocaesium fixation and can be used for prediction of this radionuclide's long-term behaviour in natural soil-water systems. Its major advantage is a small number of parameters which have a clear physical meaning and can, in principle, be determined in an independent experiment or assessed theoretically. (Author)

[en] Short communication

[en] A diffusional model of radiocaesium fixation in soils and bottom sediments was developed. According to this model fixation is a result of radiocaesium cations diffusing into the surface layer of soil or sediment particles. Good agreement between predicted and experimental time dependences of ¹³⁷Cs fixation rate in soils indicates that the proposed model seems adequately to reflect the actual mechanism of radiocaesium fixation and can be used for prediction of this radionuclide's long-term behaviour in natural soil-water systems. Its major advantage is a small number of parameters which have a clear physical meaning and can, in principle, be determined in an independent experiment or assessed theoretically. (Author)

[en] The interaction of space charge waves and surface electromagnetic oscillation is discussed for both bounded thin-layer periodic medium and semibounded medium. The effect of medium inhomogeneity on oscillation spectra is studied. Growth increments in a layer-periodic medium can exceed those in a homogeneous medium. A supposition is advanced on an existence of a new surface plasma wave having a large growth increment