Investigations of radiation exposures in the aftermath of the Chernobyl accident

Abstract

Long-term assessment of the aftermath of the Chernobyl and Fukushima accidents deals with the study of radionuclide emissions and radiation exposure in heavily polluted regions. A signifcant difference in the composition and nature of radionuclide emissions during accidents at nuclear power plants is considered in the study - a largescale radioactive fallout transfer and precipitation over the USSR and Europe took place in Chernobyl due to the uncovered core of the reactor while at Fukushima a massive emission of inert gases occurred. It is noted that based on the density of precipitation, the data indicating that the vital doses of 137Cs remain signifcantly lower or within the range of natural radiation exposure were obtained. However, due to a short half-life (8.0 days) of 131I, there are no available comprehensive measurements of 131I exposure after the accident. It is noted that retrospective dosimetry of the effect of 131I on the thyroid gland through 129I with a half-life of 15.7 Ma allows to fll the gap in this issue. 137Cs precipitation was analyzed by gamma spectrometry, 129I was studied by accelerating mass spectrometry in soil samples from 60 places in zones II and III in the north of Ukraine and the thyroid gland radiation dose in the population. Critical comparing of the results obtained with those of rare direct measurements of 131I activity in the human thyroid gland reveal that the doses are at the lower limit. The actual radiation exposure in the contaminated regions of Northern Ukraine was considered by estimating the exposure dose in returnees in the village of Khrystynivka where 30 families live and consume locally produced products in the evacuated zone II, 75 km from the Chernobyl NPP. The results show that the additional irradiation with 137Cs the returnees received was low. The possibility of safe living in heavily polluted areas is noted. Under the normal way of life, the total radiation exposure of Khrystynivka village residents was within the natural radiation exposure range. Key words: radioactive fallout, radiation exposure, radiation pollution, irradiation of returnees.