deviations of 1.68 to 1.98 (Nathans, Thews, end Russell, 1970).
With
the larger particles thus deposited as local fallout, smaller particles
e
remain in the cloud.
OQne cloud 1.5 hours after a megaton range of
explosion wt the surface of a coral island was found tohave a particle
size distribution made up of two lognormal functions, the larger particle
Ninty-one percentof the particles
were in the larger greup, which was centered around 37 microns. in
diameter, and nine percent were in the smaller group centered around
2.9 microns in diameter (Heft, 1970, p. 264).
size and composition was studied (suito, 1956).
15-megaton surface explosion.
The test was a
The fallout on the Japanese fishing
vessel Fukuru Maru consisted of calcite granules af annravimotaly
300-microns in diameter with sizes ranging mostly between 100 and
id
The Bravo test at Bikini Atoll in 1954 produced fallout whose
+ eR! 8 RTRECMEENEEY Tre. ern ema meee nes veges
*
gtoup being dominant in abundance.
As is expected, for subsurface bursts the particle sizes of
local fallout are again found to be larger than the particle sizes of
the cloud.
This was true even for one particular measurement for which
the cloud was sampled at the early time of only 15 minutes after the
nuclear explosion.
Again, lognormal distribtuions of sizes were
observed, the dominant part of the distribution in the early cloud
centered around 18-micron diameter.
In contrast, the local fallout
particles centered around 290-micron diameter (Heft, 1970, p. 271).
For nuclear explosions in the air, the cloud does not contain
~
surface materials.
Essentially all particles then consist of metal
10
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be
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pon peth ame ne:
400 microns.