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Throughout 2016 - 2021, a series of experimental studies on 137Cs uptake and excretion rate constants for the silver Prussian carp (Carassius gibelio) were conducted in the Chornobyl exclusion zone (ChEZ) under natural conditions. To confirm the metabolic parameters of 137Cs in the silver Prussian carp under strictly controlled conditions at different feed amounts real supporting laboratory experiments have been conducted. The excretion rate of the 137Cs from the silver Prussian carp increased with increasing feed amount from 0.0068 ± 0.0003 day−1 to 0.0085 ± 0.0005 day−1 at water temperatures of 26 °C. The biological half-life of 137Cs activity concentration in fish can be reduced by 2 times by increasing fish growth using clean feeding. The excretion rate of the 137Cs from the silver Prussian carp agreed with data collected in natural conditions in the ChEZ during 2016 - 2020 at different water temperatures. [ABSTRACT FROM AUTHOR]

During 2012 - 2014 sampling of soil and grain in Ivankiv district of Kyiv region at all fields adjacent to the ChNPP exclusion zone was carried out, where the cereal crops were planted. In all samples 137Cs and 90Sr activities were measured. Besides, in soil samples the exchangeable fractions of 90Sr and calcium and acidity of soil solution were determined. Dependence of 90Sr soil-grain transfer factors was specified. In conducting research works by sampling occurred 74.14-37-425:2006 SOU, SOU SOU 74.14-37-424:2006 and 01.1-37-426:2006. The activity of 90Sr was determined by standard radiochemical method. [ABSTRACT FROM AUTHOR]

Results of the study of 90Sr and 137Cs migration mobility in soils characterized with contrasting physical-chemical properties and granulometric composition has been analyzed. The mentioned radionuclides were introduced in soils in initial water-soluble form. Ecological and effective half-time of cleaning of soils 20-cm horizons (Tecol) has estimated. Mean values of Tecol 90Sr varies in limits 3.7 - 84 years. Tecol 137Cs varies in limits 61 - 265 years. Correlation of ecological half-time cleaning of soddy-podsolic soils species from radionuclide and physical-chemical properties and granulometric composition of these ones has been analyzed, strong correlation of Tecol 90Sr as well, as mean correlation of Tecol 137Cs with mentioned soils characteristics has been noted. [ABSTRACT FROM AUTHOR]

In the year 2011 sampling of soil and grain in Ivankiv district of Kyiv region at all fields adjacent to the ChNPP exclusion zone was carried out, where the cereal crops were planted. In all samples 137Cs and 90Sr activities were measured. Besides, in the soil samples the exchangeable fractions of 90Sr and calcium and acidity of the soil solution were determined. Dependence of 90Sr soil-grain transfer factors was specified. [ABSTRACT FROM AUTHOR]

To predict parameters of radionuclide resuspension, transport and deposition during forest and grassland fires, several model modules were developed and adapted. Experimental data of controlled burning of prepared experimental plots in the Chernobyl exclusion zone have been used to evaluate the prognostic power of the models. The predicted trajectories and elevations of the plume match with those visually observed during the fire experiments in the grassland and forest sites. Experimentally determined parameters could be successfully used for the calculation of the initial plume parameters which provide the tools for the description of various fire scenarios and enable prognostic calculations. In summary, the model predicts a release of some per thousand from the radionuclide inventory of the fuel material by the grassland fires. During the forest fire, up to 4% of (137)Cs and (90)Sr and up to 1% of the Pu isotopes can be released from the forest litter according to the model calculations. However, these results depend on the parameters of the fire events. In general, the modeling results are in good accordance with the experimental data. Therefore, the considered models were successfully validated and can be recommended for the assessment of the resuspension and redistribution of radionuclides during grassland and forest fires in contaminated territories.

Controlled burning of experimental plots of forest or grassland in the Chernobyl exclusion zone has been carried out in order to estimate the parameters of radionuclide resuspension, transport and deposition during forest and grassland fires and to evaluate the working conditions of firemen. An increase of several orders of magnitude of the airborne radionuclide concentration was observed in the territory near the fire area. The resuspension factor for (137)Cs and (90)Sr was determined to range from 10(-6) to 10(-5) m(-1), and for the plutonium radionuclides from 10(-7) to 10(-6) m(-1) (related to the nuclides in the combustible biomass). These values are 2 orders of magnitude lower if they are calculated relatively to the total contamination density (including the nuclides in the soil). The radionuclide fallout along the plume axis is negligible in comparison to the existing contamination. However, the additional inhalation dose for firemen exposed in the affected area can reach the level of the additional external irradiation in the period of their mission. The plutonium nuclides constitute the dominating contribution to the inhalation dose.

Representative large-scale soil sampling on a regular grid of step width about 1 km was carried out for the first time in the near zone of the Chernobyl accident (radius 36 km). An integrated map of terrestrial 90Sr contamination density in the 30 km exclusion zone (scale 1:200,000) has been created from the analysed samples. Maps of the main agrochemical characteristics of the soils, which determine the fuel particle dissolution rates and the contamination of vegetation, were produced. The total contents of 90Sr on the ground surface of the 30 km zone in Ukraine (without the reactor site and the radioactive waste storages) was about 810 TBq (8.1 x 10(+14) Bq) in 1997, which corresponds to 0.4-0.5% of the Chernobyl reactor inventory at the time of the accident. This assessment is 3-4 times lower than previous estimates.