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326 U.S. ATOMIC ENERGY
2
MO‘ORANDUM FOR DR. LIEBY, Co--issioner, United States 400
- 74
J i
(U) Measurement of Local Fall-out in Atomic Test
Operations
108065
Reference our meeting of 3 April at wich time you asked
to put down my thoughts on the meesurement of close-in fall-out
ih atomic test operations.
I am indicating below my own impressions
h this subject in the hope that tis may be of some assistance to
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(UNSLASSIFIED)
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Local Fall-out Measurements in the Nevada Test Site,
a. We have had a sufficient number of air bursts and tower
hots to prove the fact that there is no significant fall-out downwind
rless the visible fireball comes in actual contact with the ground.
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b.
The three surface and subsurface shots unfortunately,
have been in the range of 1 KT which cannot be realistically scaled
to the fall-out model for megaton weepons. What is required at
Nevada is a 50 to 100 KT clean weapon whose fission yield should not
exceed 1 tc 5 in, I believe that if such a weapon can be developed it
would go a long way in solving the many protlems of fall-out. For
example, if such a weapon could be surface detonated at the NTS, it
would definitely and perhaps once and for all determine the percentage
of gross fission product fall-out from a surface yield weapon for dry
land.
As you know, now we believe that this percentage may be anywhere
from 5 to 95 percent. Here is a factor of 19 which is unknown, If we
accept the best guesses which are fashionable today, we may say that
the total gross fission product fall-out from a land surface detonated
weapon is anywhere between 40 and 80%, but even this is a factor of 2
unknown, which needs to be pinned down. Once we determine the percentage of total fall-out of fission products we are of course, faced with
the problem o° fractionation of the various radio-nuclides such as Sr
I believe the only way to determine this mgiter is to detonate a 190 KT
weapon in the desert and to measure the Sr’~
within the fall-out region
in sufficient detail and with sufficient accuracy to make the meesurements statistically significant. I believe that once we determine the
fractionation within a 100 KT atomic cloud perhaps we can safely assure
that a simple extrapolation to the megaton case will be valid.
This of
course, is open to question, although it appears reasonable to me at
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