Cs-137 measurements for the people living near Chernobyl area

In 1991, 5 years after the Chernobyl accident, Sasagawa memorial foundation began to support Japanese medical cooperation for 5 hospitals in 5 cities in Belarus and Ukraine Republics and Russian Federation. The medical support involved the thyroid check-up, hematological examination, Cs-137 measurement in the body and epidemiological and statistical analyses for above. This report concerns the third. Subjects were 0-5 years old children at the time of the accident and >150,000 subjects received the measurement. The apparatus for measurement was Aloka WBC 101 whole body counter of chair type equipped with NaI(Tl) (7.6 x 7.6 cm) scintillation detector. The spectrum was subjected to pulse height analysis to compute the Cs-137 quantity. Measurement was done on the abdominal region. The median value was found mostly less than 50 Bq/kg while that of Japanese is only several Bq/kg. However, the internal exposure dose estimated from the body content of Cs-137 in the people near Chernobyl area (0.97 mSv/life time for man even if whose Cs-137 content=1,000 Bq/kg) was concluded to be far smaller than the dose (2 mSv/y) due to natural radiation.(K.H.)