Strontium-90 cesium-137 in rain and dry fallout (for domestic program) from Jun. 1981 to Dec. 1981

Rain and dry fallout were collected monthly on a sampling tray of approximately 5000 cm2, which was filled with water to a depth of 1 cm at the beginning of every month. The sample was filtered after strontium and cesium carriers were added. The tray was washed with 5 l of distilled water, and the washing was combined to the filtrate. The sample was passed through a cation exchange column at a rate of 80 ml/min. The preparation of a sample for analysis and the separation of strontium-90 and cesium-137 were performed. After the radiochemical separation, the mounted precipitates were counted for the activity with low background beta counters normally for 60 min. Net sample counting rates were corrected for counter efficiency, recovery, self absorption and decay, to obtain the content of strontium-90 and cesium-137 radioactivity per sample aliquot. From the results, the concentrations of these nuclides in the original sample were calculated. The maximum values obtained were 0.56 mCi/km2 of Sr-90 in Matsue and 0.17 mCi/km2 of Cs-137 in Ojika-gun, Miyagi, in June, 1981. (Kako, I.)