~2the lower part, the tropospnere -- while the kiloton yield fire- balls stabilize below the tsopopause. The tropopause normally occurs at somethin, Like 4¥,J0U to 59,300 feet altitude, although it depends on season and location. In other words, iow yield bombs fired in the stratosphere would ve expected to give the same fallout rates as high yielu weapons do when fired in the troposphere -- or on the surface. There is some small: part of the fallout, ever. for mezaton yield explosions, which does come down from the troposphere. The stratospheric debris descends very slowly unless, of course, it is so large as to fail in the first few hours. This paper is concerned only with the world-wide fallout -- that is, the faliout which does not occur in the first few hours and excludes the iocal faliout which constitutes the famous elliptical pettern which is so hazardous because of its radiation intensity, but which, in test operations, is carefully restricted to test areas. It is worth mentioning in passing that the local fali- out may be the principai hazard in the case of nuclear war. Most serious attention should be paid to it in civilian defense programs. Il, WORLD-WIDE FALLOUT MECHANISM The world-wide fallout from the stratosphere occurs at a slow rate. The cate of descent of the tiny particles produced by the detonation. is so smail that something like five to ten po BOSE DO® ARCHIVES

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