Results of researches of aerosol filters exposed in the near region of the Chernobyl atomic power station before destruction of the machine house roof of 4-th block in February 2013 are presented. Significant rise of beta and gamma activity (more than on 3 orders) that refer to time of destruction was registered on filters. Autoradiograms of the filters' fragments show great rise (? 2 orders) of the "hot" particles amount. Dispersion analysis of the found "hot" particles indicates considerable contribution of great number of particles with rather small activities (0,15?3 Bk) to the general activity. At present time corresponding activity have particles of irradiated nuclear fuel 2,36 ? 6,19 microns in diameter. Taking into account the meteorological data received near the Object " Ukryttya ", prospective motion trajectory of the centre of cloud of exhaust was calculated. Assessments of the total beta and gamma activities of exhaust were made in approach of an instant point source. Estimation of specific activity of air on an axis of a trajectory of cloud in a region of building of a protective construction over the reactor of 4-th block was made. It was shown that received values essentially exceed maximum permissible levels. Ranges of flight of "hot" particles were also calculated. The kinetic of dissolution of "hot" aerosol particles in the simulant lung fluid was investigated. It was shown that about 13 % 137Cs aerosol particles is in a kind of instant fraction, that is typical for space under machine house roofing.
Keywords: object "Ukryttya", "hot" particles, autoradiography, specific activity of air, dissolution kinetics in lung fluid
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