9,
'Fall-out" problems in the employment of thermonuclear and fission
weapons.
This Committees has long been concerned with the question of
the deposition of radioactive preducts whichresult from nuclear explo-
4sions_onsolidgroundand in the
oir ii (oy.
fos 1D
As a result of our discussion with Dr. Bugher, Gen. Luedecke, Dr,
Scoville, Col, Kaesser, Capt. Maynard, and Dr. Machta, we came to the
conclusion that for the very large weapons exploded near the ground
or near the surface of water, a large fraction of the radioactive
material produced falls out over an area which is conditioned by the
wind structure at the time of the explosion, This area scales up from
the results of tests already made in Nevada from much smaller weapons;
and it is almost inevitable that an atomic explosion, where a substantial portion of the fireball reaches the surface, will result in
a heavy and lethal fall-out. o¥er an area much greater by a factor up
to 10 than the area of blast damage,
Therefore, weapons exploded at
an altitude of 14, or greatet, times the radius of the fireball will
not result in a high degree of local fall-out, but in a wide distribution of fall-out over a long period of time; " Although these gross
affects just described appear to be tinderstood, the details are not
at all well understood, e.g; the amount of fractionation of radioactive
material which falls cut, ahd the decay time of the fall-out material
in different regions. We | guggest-that the fall-out studies merit .
continued support and attention.
The Committee r
nas that, when the fall-out phenomenon from
low bursts is better understood, other Government agencies and the
public should be informed of the facts,
It 1s clear that if this ~.
country were involved in war, with a power which possesses thermonuclear
weapons, fall-out from low thermonuclear bursts couldbave very serious —
esultsifwe..wereunpreparedto meet the situation. J
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Meitis hardly necessaryto point out the importance, :
“andourpresenthitah ‘iogree of ignorance, of this problem, Some of our
members pointed out the implications of the results of these tests insofar
as defense is concerned. Since the effects of fall-out were strongly
felt at a distance of 300 miles, present plans for polnt—defense of
important targets may have to be re-evaluated in the light
results,
10,
Two other recommendations on the subjects of the test
of these
7
program,
and the "L" area have already been transmitted to you, and are herewith
appended for the record,
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