ASSOCIATION OF THE CHERNOBYL FALLOUT ISOTOPES PATTERNS WITH THOSE OF RAINFALL IN GREECE

A wide soil-sampling programme was undertaken right after the Chernobyl accident in Greece by the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA), in order to detect and quantitatively analyse the long-lived radionuclides in the Chernobyl fallout. Samples (1242) of 1cm thick surface soil were collected[1] all over Greece during the period from May to November 1986. The samples were counted and analysed using Ge detector set-ups. An in-house unix-based data base/geographical information system was developed for the detailed mapping of the ten radionuclides 137Cs, 134Cs, 144Ce, 141Ce 125Sb, 106Ru, 103Ru, 95Zr, 110mAg and 54Mn mainly deposited in Greece. Multi-fractal analysis has also been performed. This analysis has already been published ([2],[3]) and showed that there exist differences in the spatial distribution of the above radionuclides. These differences are primarily attributed to different deposition pathways and mechanisms and different arrival dates. In the present work, a statistical technique to compare contour maps is introduced and applied to explain the differences,in the fallout patterns of the above-mentioned radionuclides. As a result of this analysis, it was made clear that there are two main subsets of radionuclides (a): 137Cs, 134Cs, 144Ce, 141Ce 125Sb, 106Ru, 103Ru and 95Zr, and (b):110mAg and 54Mn, deposited in distinct ways. Furthermore, the weekly rainfall during the period from April 26th to May 30th was mapped. Multifractal analysis of the rainfall patterns has also been performed. The above two radionuclide subsets, were compared with the rainfall patterns using an introduced statistical technique. As a result, the pattern overlapping ratio was calculated and it was concluded that the 137Cs subset was deposited during the week May 3rd - 9th, 1986, while the 110mAg subset was deposited during the following week May 10th -16th, 1986.