RESUSPENSION OF FALLOUT MATERIAL FOLLOWING THE CHERNOBYL ACCIDENT

Air concentration and surface contamination data have been collected from a cross-section of sites across Europe where measurements have been made for 2 or 3 years after the Chernobyl accident. Data for over 20 European sites are considered; for U.K. sites data up to 1992 have been analysed. The results have shown that Cs-137 derived from Chernobyl could be measured in air up to 6 years after deposition. Values of the resuspension factor (K) have been calculated and show a reduction with time at all sites. The decrease in K could be described by an exponential function (time constant = 0.02 to 0.12 month-1) or a power law (with an exponent about - 0.5 to - 1.0), with similar degrees of correlation. A systematic decrease in K at sites with increasing deposition was also observed. In the first year after the accident, the time integral of the deposition flux was a large fraction of the initial deposition. Depending upon the site, between 0.01 and 1.0 times the initial deposit was accumulated in deposition collectors. This represents a significant contamination risk well after the original deposition event. Evidence suggests, however, that the length scale for transport of most of the resuspended material is very limited.