COLLIMATED DETECTOR TECHNIQUE FOR MEASURING A CS-137 DEPOSIT IN SOIL UNDER A CLEAN PROTECTED LAYER

A method to determine the Cs-137 soil deposit in situ where the contam ination is covered by a clean soil layer is described. The method is b ased on measurements of the count rates in three energy ranges by a co llimated spectrum sensitive detector and their processing. The deposit determination accuracy is 20%. The measurement results are presented and compared with data from soil sampling. The Cs-137 contamination ma ps of areas in Belarus and the Chelyabinsk region of Russia are presen ted. Measurements of the river Techa bank contamination detected the p resence of secondary contamination. This method permits the change of dose rate after land decontamination and the work needed for decontami nation and its efficiency to be predicted. (C) 1997 Elsevier Science L td. All rights reserved.