著者

真室 哲雄 藤田 晃 松並 忠男 吉川 和子 東 俊雄

出版者

Atomic Energy Society of Japan

雑誌

日本原子力学会誌 (ISSN:00047120)

巻号頁・発行日

vol.4, no.5, pp.299-307, 1962

被引用文献数

3

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It has been generally considered that the radioactive air-borne dusts, which are produced by a nuclear explosion and reach an area far distant from the test ground, are very fine and that their radioactivities are distributed in the atmosphere comparatively uniformly. But, after the reopening of the nuclear test explosions by U.S.S.R. on September of 1961, the measured values of radioactivity in rain water differed much from each other, even though they were obtained at nearby laboratories at the same time. Moreover, it was reported that strongly radioactive particles, the counting. rates of which exceeded 10, 000 cpm, were found on the roof after rain fall by a GM counter at Niigata University. In order to reveal this question, we took the autoradiographs of the air-borne dusts collected on filter papers. It was concluded that the radioactive air-borne dusts produced by a nuclear explosion were composed of many particles having radioactivities quite various in magnitude and that strongly radioactive particles were present even in long-range fallout especially just after a nuclear explosion. This situation is in marked contrast to that observed in the natural radioactivities which are distributed in the atmosphere quite uniformly. Under these circumstances, following problems are proposed.<br>(1) Is it unnecessary to establish the standard method for the accurate measurement of fallout especially just after a large scale nuclear explosion?<br>(2) Does'nt it make mistake from the view point of the radiological protection to base on the today's M.P.C., even when the radioactive fallout visits in the manner stated above?