Radionuclide Ratios in Precipitation on the Territory of Belarus After the Chernobyl Accident: Calculation from Gamma-Spectrometric Measurements on Soil in May–July 1986

The correlations between the fallout density and ratio of radionuclides in different regions of Belarus after the accident at the Chernobyl NPP are investigated using data obtained by means of gamma-spectrometric measurements performed on soil in May–July 1986. It is shown that the isotopes of cesium and/or ruthenium are most suitable for reconstructing the activity of 131 I in the fallout. Charts showing the isolines of the activity ratios 131 I/ 137 Cs and 134 Cs/ 137 Cs in the fallout are constructed. The geometric averages obtained for the log-normal distribution of the ratios 134 Cs/ 137 Cs and 131 I/ 137 Cs in terms of May 10, 1986 equal 0.47 and 5.4, respectively. The distribution of the activity ratio 131 I/ 137 Cs in the fallout and the correlation coefficients show that on the whole there is no consistent interrelation between the fallout indices of these radionuclides over the territory.