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to 1700° c).
The fallout particles in this case consisted of transparent
glass drops with an outer zone of intensely colored, radioactive glass
formed by solution of the iron from the tower and the radioactive elements
in the fused soil drops.
With this process in mind, an experiment was devised in which a series
of high-melting
tracer minerals were to be introduced into the natural
soil surrounding the tower for a shot of appropriate size. It was anticipated that these tracer minerals would be drawn up into the cooling fireball
and act as collecting surfaces for the condensing radioactive elements. By
using tracer minerals which had considerably higher melting points than the
Nevada soil minerals it was hoped that these higher-melting species would
enter the cooling fireball and collect some of the condensing radioactive
elements but would not be heated sufficiently to melt. By collecting fall-~
out particles from this shot and noting which of the tracer minerals had
collected radioactivity but had not melted, it would be possible to tell
approximately at what temperature condensation was taking place.
Accordingly, 14 tons of tracer minerals were distributed around the
tower of the shot at Eniwetok whose fallout is described in this report.
The pertinent data concerning these minerals are given in Table 1.
These minerals had been ground and sieved and only material whose
particle size was about 0.8 mm in diameter or less was used. The minerals
were scattered lightly over the top of the ground in areas extending from
the base of the tower out to about 150 yards. The natural coral soil at
Eniwetok furnished caleium oxide, which melts at 2570° C, as the highestmelting member of the series.
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In the description of the formation of the fallout particles given
above little attention has been paid to the behavior of the radioactive
elements themselves. These radioactive elements are present in such small
quantities that they may be considered as trace constituents and do not
affect the main course of fallout particle formation. However, as an
initial stepina more detailed study of the condensation of the vaporized radioactive elements, it was desired to know something about the tempera~
ture range in the fireball at which they condense. The general process of
fallout particle formation described in this report, in which melted soil
particles act as collecting surfaces for the radioactive elements in the
fireball, had beenpreviouslyobserved at a tower shot at the Nevada Test
Site. The soil at the Nevada Test Site consists mostly of silicate .
minerals which melt at comparatively low temperatures (approximately 1200
BF]
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