THE BEHAVIOR OF CHERNOBYL CS-137, CS-134 AND RU-106 IN UNDISTURBED SOIL - IMPLICATIONS FOR EXTERNAL RADIATION

Following the Chernobyl accident, deposits of Cs-137, Cs-134 and Ru-10 6 on exposed surfaces in urban areas were found to be the major contri butors to the external radiation dose. The fixation of these radionucl ides in soils was investigated by the determination of their vertical distribution in and through sequential extractions. Four years after t he Chernobyl accident it was found that most of the caesium remained f irmly fixed in the topmost 2 cm. In the deeper layers of the soil it w as less strongly bound. The ruthenium was found to be less strongly bo und than the caesium and had penetrated a little deeper. The study ind icates the need for countermeasures if the long-term radiation dose to the local populace is to be reduced significantly.