Measurement of Cs-137 body content of the residents near Chernobyl

The authors were in charge of measuring Cs-137 body content which was one of 4 examination projects made 5 years after the Chernobyl Accident. Measurement was done by Aloka WBC101 whole body counter of chair type equipped with the detector of NaI(Tl), 7.6 cm in diameter x 7.6 cm in length, shielded with lead. The radiation spectrum gained in the multi-channel analyzer was computed to give the amount of Cs-137. The abdomen was subjected to actual measurement, whose measured value was converted to the whole body content by the calibration graph obtained with age-dependent phantoms. Five medical facilities of Gomel, Mogilev, Klincy, Kiev and Korosten examined 26,664 males and 28,917 females in total in the period of May, 1991 - December, 1993. The body content measured in the 5 centers was mostly <50 Bq/kg, which was independent on age or sex. However, the median values were larger than 100 Bq/kg in same villages of Gomel prefecture, which had been radio-contaminated most severely. Despite this, the present body content of Cs-137 was concluded to be enough small when we consider that the life-long radiation dose derived from 1,000 Bq/kg of Cs-137 was 0.97 mSv and the natural radiation dose was 2 mSv/y. (H.O.)