Application of long-living radionuclides for radiation situation reconstruction on a nuclear accidents active stage

In this work the reconstruction of radiation situation in the Republic of Belarus at Chernobyl accident active stage by iodine-129 content was carried out. By the methods of neutron-activation analysis and mass spectroscopy with linear accelerator the iodine-129 content in soil surface layer from 52 settlements on different distances and directions from the accident place both before and after Chernobyl catastrophe were determined. It is shown, that 'before-Chernobyl' Belarus soils contamination levels by iodine-129 makes up 94±15 μBq/kg, and the 'Chernobyl ratio' of 129I/131I in the Belarus soils at the accident moment is equal 15.2±4.7 g/g. In the result of conducted examinations it was revealed, that and after 10-12 years after the accident the 129I and 137Cs radionuclides fractionation had not occurred, and more than 85 % activity of these radionuclides is in upper soils layers (20-25 cm). The methodical approach to determination of iodine-131 in the thyroid of the Belarus population on the Chernobyl accident active stage is developed. For revealing of pathway (inhalation and peroral) and possibilities for 131I incoming in the thyroid of some inhabitants of Minsk city a number of variants with diverse circumstantiation of isotope fractionation are considered