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Other radioactive nuclear explosives that vere unconsumed in the
nuclear explosion, for example uranium-235.
The physical dimensions and the chemical composition of these radioactive particles from the tests (Freiling, 1965) depend upon where the
nuclear explosion occurred.
In particular,
the composition differs if
the test was over land compared to tests either over water or under
water (Glasstone, 1964, and Heft, 1970).
The fireballs from nuclear
explosions over ground suck up vast quantities of soil and other materials.
Due to the high temperature, these rise as a vapor in the fireball and
cloud.
The fission products are initially also vapors and these condense
onto both solid and molten soil particles resulting from cooling and
condensing.
During the cooling, the more refractory
tion temperature) materials condense first.
(higher vaporiza-
For example, fission products
that are gaseous or have gascous progenitors,or precursors,
(parent
element before beta-particle decay transmutation into a daughter element)
adhere or are incorporated lastto the fallout particles during these
processes,
In general,
this selective attachment of radioactive atoms to
fallout material is called "fractionation."
tionation is shown,
The occurrence of frac-
for example, by the fact that in a land surface
burst the larger particles, which fall out of the cloud at early times
and are found near ground zero, have radiological properties different
from the smaller particles that leave the radioactive cloud at later