MEMORANDUM FOR DR. BUGHER
SUBJECT:
(U) Radioactive Fallout
1. In the inclosed report I have analyzed the fallout from the first
shot of CASTLE Test Operation, I am amazed at the similarity of thisevent
with the fallout at Nevada. As a matter of fact, if the JANGLE - Fallout
Model had been simply extrapolated to the CASTLE Bravo yield by a straight
line extrapolation (where distance is proportional to the third power of
the yield and fallout area is proportional to the two thirds power of the
yield) then I'm sure that the CASTLE Bravo shot would not have been fired,
extrapolation is used. This fact is further brought out by the fallout plot
prepared by the CASTLE Rad Safe organization after the Bravo event utilizing
the ARDC method of elliptical approximation indicated in ARDC Report C3-36417
and its supplement,
2.
(i
4A closer look at the actual Bravo fallout brings out the curious
fact that as the yield is increased, and the height of burst is kept cone
stant, the distribution of ectivity within the stonic cloud changes,
For
exaaple, in the JA4NGLE - Surface shot, analysis of the fallout shows that
approximately 40% of the activity resided in the mushroom and 40% in the
stem, dowever, analysis of CASTLE Bravo fallout shows that approximately
80% of the fallout cones from the stem, This leaves only 20% of the activity
in the mushroom, Since it is essumed that 10% of the activity is non~
scavenzabdle by the soil debris, this means that within 24 hours, 75% of the
fallout is from the stem and only 5% from the mushroom, This curious
shifting of the immediately scavengable activity from the mushroom to the
stem was evident in the Nevada Shots, During TUMSLER/SNAPPER Test Operation,
the average activity in the stem and mushroom was approximately 5% each.
During UPSHOT/KNOTHOLE Test Operation, however, the activity in the stem
increased to 10 or 15% but the activity of the mushroom still remained at 5%.
The tower heights of both test operations were 300 ft, but the yields were
different
@ this trend which was first noticed in kh =
is verified in the Pacific Tests.
(Sa
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3. Another curious factor that really puzzles me is the assumption
made by many people that Bikini Atoll islands were contaminated by the upwind end cross-wind components of the fallout from the first shot of CASTLE
I cannot find any evidence of this, Bikini 4toll was in the downwind di- >
rection.
‘That contaminated the Bikini Islands was the downwind fallout
E ARCHI
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This is because all Bikini atoll islands and the islands of Rongerik, Rongelap, and Bikar are clearly in the fallout area even when such a simple
which came from 10,000 ft to 20,000 ft above sea level. Curiously enough,
in none of the subsequent barge shots, was ground zero or the lagoon or
the imnediate test area in the downwind path. I am afraid that this has
given rise to the misconception that barge(or water) surface shots are less
contaminating than lend surface shots. I feel confident that if the first /,
shotwof CASTLE were fired on the legoon waters it would have severely contaminated the Sikini Islands. The downwind contamination would have extended further out and covered more area, but the time of fallout would
5
have been deleyed by a factor of 2. Although a shift of wind is blamed
we
for the unexpected contemination of Rongelep and Rongerik, there is no
C4-25581
0) NZOLYZ