Probabilistic trajectory and dose analysis for Finland due to hypothetical radioactive releases at Sosnovyy Bor

The Chernobyl accident initiated a wide international interest in developing long range transport models for assessment of radiological consequences due to airborne releases. The Finnish TRADOS computer model had been developed to calculate long range atmospheric dispersion and resulting doses via several exposure pathways. During and after the Chernobyl release the code was utilized to make an initial estimate of the release magnitude and to predict both individual and collective doses in Finland. These calculations proved that the TRADOS system is also well applicable in the acute phase of an accident. In the present study the analysis of atmospheric dispersion to Finland from Sosnovyy Bor near Leningrad and the pertinent dose predictions due to a reactor accident in this area have been made. Both the Chernobyl type release and a smaller release typical of a modern light water reactor at the RBMK-1000 power plant site are considered. The results are compared with the previous studies, in which a smaller release from a light water reactor accident had been assumed to take place in northern Germany and in eastern Sweden (Forsmark). According to the analysis of the number of annual trajectories arriving to Finland from Leningrad this number is with a factor of two less than that for a site in eastern Sweden. Taking this fact into account the radiological risks to Finland seem to be approximately equal when the same release is assumed to have occurred either in Leningrad or in eastern Sweden. Acute health effects in Finland are not caused in either case.