deviations of 1.68 to 1.98 (Nathans, Thews, end Russell, 1970).
With
the larger particles thus deposited as local fallout, smaller particles
vr
remain in the cloud.
One cloud 1.5 hours after a megaton range of
explosion «t the surface of a coral island was found to have a particle
size distribution made up of two lognormal functions, the larger particle
group being dominant in abundance.
Ninty-one percent of the particles
were in the larger group, 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).
The Bravo test at Bikini Atoll in 1954 produced fallout whose
size and composition was studicd (Suito, 1956).
15-megaton surface explosion.
The test was a
The fallout on the Japanese fishing
vessel Fukuru Maru consisted of calcite grannies af annravimotaly
300-microns in diameter with sizes ranging mostly between 100 and
400 microns.
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 whicn
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
ARENe IR Fare eer ne Se ete ema
nuclear explosion.
ee Ae SaterRR aN Ree
the cloud was sampled at the early time of only 15 minutes after the