MODELING OF CS-137 CYCLING IN FORESTS - RECENT DEVELOPMENTS AND RESEARCH NEEDED

After the Chernobyl nuclear reactor accident in April 1986, Cs-137 was found to be one of the most abundant radionuclides released and the forest ecosystem was one of the most contaminated environments. Long-term management of the forests to minimize the radiation dose to man requires understanding of the cycles of the Cs-137 and the other radionuclides which were also deposited. Thus, the health physicists responsible for remediation programs in the contaminated zones must have information on the long-term behaviour of the deposited radioactivity. The similarity between the chemical properties of Cs and K and the fact that K has been studied previously as a nutrient in forest productivity may provide an analogue to evaluate the long-term mechanism of the deposited radioactivity. One of the goals of this study is to describe the global cycle of K in forests related to the Cs-137 contaminant. The first results of an experimental program to measure the deposition of Cs-137 in the several forest compartments is presented, together with the complementary K results. These data provide information which is necessary to construct a useable model describing the Cs-137-transfer after atmospheric contamination of a woodland ecosystem.