Chapter 4
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CONCLUSIONS AND RECOMMENDATIONS
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4.1 CONCLUSIONS
The failure of the rocket sampling program made it necessary to rely almost exclusively
upon the techniques of relative enrichmentof volatile material in an isolated portion of the cloud
for the measurement of fallout partition. This technique is an unproved one that includes some
rather bold assumptions and a number of experimental difficulties.
It was not possible to sample at altitudes as high as desirable, and differences in cloud height
with energy release and their subsequenteffects upon fallo partition were not clearly defined.
However, with these reservations, it is concluded that the technique generated a reasonably
consistent body of data that was interpretable in the fashion expected.
The pattern of progressive enrichment of volatile material in an {solated portion of the cloud
was displayed in Shot Walnut on a rather long time scale. However, if progressive enrichment
occurred in Shots Koa and Oak, it was on a time scale short compared to 2 hours. Because the
program for early sampling by rockets was not successful, no information was obtained on a
time-dependent effect in the direction of enrichment.
1.
The results suggest that, for a 1.21-Mt device (Koa) detonated on a coral surface, about
one-fifth of the Sr” formed ta dispersed over distances greater than 4,000 miles. For a device
@etonated on a modified ocean surface (sand-filled barge), the
Irgvction increases to about one-third. A device with a 9-Mt yield (Oak) in shallow water over
a coral reef also disperses about one-third of the Sr™ produced at distances greater than 4,000
miles.
2. Fractions of Cs'*’ corresponding to those given above for Sr” are about two-thirds
dispersed for Koa, about one-third for Walnut, and about one-half for Oak.
Beside the obvious environmental differences in these detonations, the following are some
of the factors that may have an effect on the fractions of various radionuclides that are widely
dispersed: (a) An 8.9-Mt device produces a concentration of debris in the cloud volume lower
by about a factor of 2 than the smaller devices studied here. (b) The time tt takes the fireball
to cool to 1,000° C was about three times as long for Oak as for Koa and Walnut. (c) The size
distributions of the fallout particles may well be different for devices of different yield even
though shot environment is similar. (d) The largest yteld device had an appreciably larger
fraction of its resulting cloud in the stratosphere where high-velocity winds could effect greater
dispersion. (e) The different chemical and physical nature of the fallout particles may make
for different distributions of various radionuclides between local and worldwide fallout.
3. Radionuclide fractionation is pronounced in shots over a coral land surface. The local
fallout is depleted in both Sr™ and Cs'*’, while the upper portion of the clouds are enriched.
Fractionation is much less for water-surface shots.
4. Nuclear clouds are nonuniform in composition, and certain nuclide ratios vary by rather
large amounts from top to bottom. Again, this is much larger for detonations on land than on
water surfaces.
.
5. The radiochemical studies of fine and coarse particles indicate that the fission products
with rare-gas precursors—Sr®®, sr®, y"!, and Cs5’are in general more concentrated in the
fine particles in the land and reef shots.
In the water-surface shot, they appear to be more
evenly distributed among the particle groups.
8. Sr® and Cs‘*” distributions computed from cloud and fallout data are roughly in agree-
ment with one another.
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