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Various units have been used to express exposure to radiation
such as the roentgen, rep, rem, and rad.
All are intended to express
some relationship between radiation energy absorbed and biological
effects.
Since it is not critical for the following discussions to
understand the technical differences among the units, only the “"roentgen" will be used.
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To provide some perspective as to the magnitude
of the "roentgen" of exposure the following table (Table 1) is included.
area
(Table 1.)
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2.
Sources and Nature of Fallout.
The major source of radioactive materials in fallout is the fissioning or splitting of atoms of uranium and plutonium, forming a large
number of unstable radionuclides.
Other induced radioactive products
result from inert materials capturing neutrons that are released during
either the fission or fusion process.
(Fusion is the process wherein
hydrogen nuclei are joined together.)
Generally, these induced radio-
active materials are relatively short-lived and contribute only ina
minor way to radiation exposures to man.
The principal exception is
carbon-14 described in Section I. F. (Page 20
).
Some of these nuclides escape as gases and are dispersed and
diluted in the atmosphere.
—— K
Most of the fission products, however,
become incorporated into or attached onto minute inert particles of dust
and debris from the immediate environment of the bomb.
The dust par-
ticles, together with the associated radioactive nuclides, are swept