On the basis of the work (ground investigations and gamma aerial surveys) carried out jointly by the Rosgidromet organizations and Berezovgeologiya, data on the radiation exposure in Russia were obtained shortly after the accident of April 6, 1993 already. These data were transmitted to interested institutions. The measurements performed on April 11 and 12,1993 indicated that within the isolines of 10 /μR/h a contaminated area of up to 25 km in length and up to 6 km in width extended towards the northeastern direction. Thus, the contaminated area outside of the premises of the combine covered about 100 km2. The total amount of radioactive substances in this area was 530 - 590 Ci. Isotope composition of the radioactive trace was determined by ruthenium-103 (1%), ruthenium-106 (31%), zirconium-95 (22%), niobium-95 (45%) and plutonium-239 (0.02%). Contamination heterogeneity is caused by the existence of "hot" particles with an activity of up to 10-11 Ci/particle. In the contaminated area the gamma exposure rate varied between 14 and 42 /μR/h at 1 m height, yielding the maximum external radiation dose 100 mrem/year for the population of Georgievka. The Pu-239 inhalation dose of the population of Georgievka when passing the radioactive cloud did not exceed 1.5 mrem. A prognosis was made with regard to water contamination of the rivers Samuska and Tom during the flood in spring. Furthermore, contamination of the air layer adjacent to the ground resulting from the wind transport of radionuclides in the summer months at Georgievka was predicted. The values were far below the limits fixed according to the valid radiation protection regulations. However, that radionuclide concentration of the snow water may exceed the limits specified for drinking water. According to the data measured by the meteorological stations, the radioactive products were not entrained beyond the borders of the country. Source estimation was successfully obtained using RIMPUFF, the Rise on-line puff diffusion model, in backfitting mode.
|Place of Publication||Roskilde|
|Publisher||Risø National Laboratory|
|Number of pages||47|
|Publication status||Published - 1994|
|Series||Denmark. Forskningscenter Risoe. Risoe-R|