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INTRODUCTION
A study has been made of the chemical composition, structure and
distribution of radioactivity in the radioactive fallout particles resulting from a moderate-yield tower shot in Operation REDWING at the Eniwetok
Proving Grounds.
fo collect samples of the radioactive fallout, large, open trays were
placed on several of the islands which extended along the atoll for a few
miles on each side of the shot point. On only one of these islands,
approximately ten miles from the shot point, was fallout sufficiently heavy
to provide abundant samples of the fallout particles. The trays from this
island were picked up, secured for transportation and shipped to this
laboratory.
In order to study the radioactive fallout particles it was necessary
first to separate them from the inactive sand grains which had been swept
into the open trays by surface winds. This was done by removing al11 the
particles from the trays and sprinkling them onto the backs of pieces of
single-~coated X-ray sheet film. Just before dispersing the particles onto
the film, the film had been sprayed with a thin layer of liquid plastic
which, after hardening, held the scattered particles onto the film.
After
an exposure of a few hours the films were developed and fixed by brushing
the appropriate solutions onto the emulsion side of the film, with care
not to disturb the particles on the other side. The radioactive particles
were easily identified by the halo of darkened film surrounding them.
Many of the radioactive particles were then removed from the films and
mounted in small plastic pellets which were then ground into thin sections
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with standard petrological techniques.
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These sections, which were cut
through the center of each particle, were about 30 p thick. By studying
these thin sections under the petrographic microscope it was possible to
identify the transparent compounds and to observe the structure of the
fallout particles. The opaque compounds in the particles were identified
by X-ray diffraction analysis. The distribution of radioactivity within
the particles was found by radioautographing the thin sections with
Eastman NIB stripping film.
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