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contamination will extend depends on the yield off the weapon, and
may be expected to cover at least the area boundeR
limits of the D-ring of >iast damage.
It will p
by the outer
bably be of a
high degree of radioactivity.
Outside the zone of close-in contamination]
radioactive
fallout can be expected to occur progressively inj
the direction
of the effective wind over a number of hours and
Bver an area of
@ great many square miles.
The radioactive material may or may
not be visible but can be detected with radiologifal monitoring
instruments.
Falling dust or ash, if visible, will most likely be
radioactive,
The intensity of the radioactivity is very
high immediately
after the burst, but "decays" or diminishes rapidly.
Therefore,
since not much time will have elapsed, the partidles reaching the
ground near the burst will be very highly radioadtive while those
which are carried a long distance will have lost
Pmuch of their
radioactivity before they alight.
The fallout material on the ground, of cotirse, continues
its radioactive decay.
After 24 hours the rate
@f radiation per
hour based on the decay rate formula given in "Tie Effects of
Atomic Weapons", published by the U.S. Atomic En@rgy Commission,
September 1950, 1s about 2% of the rate at one h@ur after the
burst.
This may still bevery dangerous at somefpoints, however.
B. Energy Range of Residual Radiation
Radiation emitted from fallout is of a vorer penetrating
power than the initial radiation produced at theftime of bomb
detonation.
Therefore, the effectiveness of @ given thichness of
shielding will be greater for residual than for
[nitiel nuclear
radiation.
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DPE ARCHIVES
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