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3-
Radionuclide fractionation is pronounced in shots over a coral land
surface.
The local fallout is depleted in both sr?9 and cs¥7, while the upper
portions of the clouds are enriched.
Fractionation is much less for water surface
shots.
4.
Nuclear clouds are non-uniform in composition and certain nuclide ratios
vary by rather large amounts from top to bottom.
Again, this is much larger for
land than water surface detonations.
5.
The radiochemical studies of fine and coarse particles indicate that
the fission products with rare gas precursors, sr®? | sr70, y71, and csi37 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.
6.
sr? ana cst? distributions computed from cloud and fallout data are
roughly in agreement with one another.
4.2
RECOMMENDATIONS
The ratio of local to world-wide fallout is essentially governed by the
distribution of particles with respect to size and altitude in the cloud at
stabilization (i.e. at an early time before appreciable fallout has occurred),
and the specific activity of radionuclides of interest as a function of particle
size.
The latter function may vary with altitude in the cloud at stabilization.
The basic types of information necessary to calculate the fractions of a
given radionuclide in local and worldwide fallout from particulate samples are:
1)
the particle size at which division into local and worldwide fallout
occurs for each sample