Radioactivity caused by the 21st nuclear test in People's Republic of China

The radioactivity in the suspended dust at high altitude, rain water, suspended dust and falling dust, and 131-I in raw milk caused by the 21st nuclear test in People's Republic of China were investigated during the period from November 18 to 25, 1976. The monitoring posts were two stations of the Meteorological Agency, Japan Atomic Energy Research Institute and 19 prefectures. The radioactivity in the suspended dust at high altitude was 1.34 +- 0.03 pCi/m3 at the altitude of 38,000 ft in northern Japan (Misawa), 0.15 to 0.63 +- 0.02 pCi/m3 at the altitude of 25,000 ft in middle Japan (Iruma), and 0.24 +- 0.01 pCi/m3 at the altitude of 20,000 ft in west Japan (Tsuiki). Rain water and dust showed approximately same values as normal values, excepting three prefectures which showed slightly larger values. Suspended dust showed a little larger value than the usual value in Hiroshima. The result in falling dust was same as normal. The investigation showed a little effect on the rain water and the suspended dust on the earth surface, but the radioactivity was lower than the standard determined by the radioactivity countermeasure center. The 131-I in raw milk was less than the detection limit according to the agricultural institutes in Chiba, Sapporo and Kumamoto, Japan Atomic Energy Research Institute, and other seven prefectures, from November 19 to 24 or 25. (Iwakiri, K.)