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 f orest ecosystem was one of the most contaminated environments. Long-te rm management of the forests to minimize the radiation dose to man req uires understanding of the cycles of the Cs-137 and the other radionuc lides which were also deposited. Thus, the health physicists responsib le for remediation programs in the contaminated zones must have inform ation on the long-term behaviour of the deposited radioactivity. The s imilarity between the chemical properties of Cs and K and the fact tha t K has been studied previously as a nutrient in forest productivity m ay provide an analogue to evaluate the long-term mechanism of the depo sited 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 f irst results of an experimental program to measure the deposition of C s-137 in the several forest compartments is presented, together with t he complementary K results. These data provide information which is ne cessary to construct a useable model describing the Cs-137-transfer af ter atmospheric contamination of a woodland ecosystem.