A DYNAMIC-MODEL FOR EVALUATING RADIONUCLIDE DISTRIBUTION IN FORESTS FROM NUCLEAR ACCIDENTS

The Chernobyl Nuclear Power Plant accident in 1986 caused radionuclide contamination in most countries in Eastern and Western Europe. A prim e example is Belarus where 23% of the total land area received chronic levels; about 1.5 x 10(6) ha of forested lands were contaminated with 40-190 kBq m(-2) and 2.5 x 10(4) ha received greater than 1,480 kBq m (-2) of Cs-137 and other long-lived radionuclides such as Sr-90 and Pu -239,Pu-240. Since the radiological dose to the forest ecosystem, will tend to accumulate over long time periods (decades to centuries), we need to determine what countermeasures can be taken to limit this dose so that the affected regions can, once again, safely provide habitat and natural forest products, To address some of these problems, our in itial objective is to formulate a generic model, FORESTPATH, which des cribes the major kinetic processes and pathways of radionuclide moveme nt in forests and natural ecosystems and which can be used to predict future radionuclide concentrations, The model calculates the time-depe ndent radionuclide concentrations in different compartments of the for est ecosystem based on the information available on residence half-tim es in two forest types: coniferous and deciduous, The results show tha t the model reproduces well the radionuclide cycling pattern found in the literature for deciduous and coniferous forests, Variability analy sis was used to access the relative importance of specific parameter v alues in the generic model performance. The FORESTPASTH model can be e asily adjusted for site-specific applications.