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. “Very little exnerinental data exists on the’ scavenging action of ralae
on the atomic cloud. Hence it is possible to prepare a logical study undera
a given set of assumptions to show that rain has the capability of scavenging. <
out sufficient radioactivity from the atomiccloud to projuce a definite ~*.:)
hazard to life. On tteother hand, if it’s assumed that the radioactivity‘2.
scavenged out by rain is not confined toa relatively. smal] ‘surface area, “-* ©”
then a stily could be prepared to show that the radioactive contamination’ Rie
" produced by rain fs relatively unimportant.
Since there is.‘very little. 3:7
quantitative data on the scavengingaction of rain, an attempt is wade in - .
a this report to study the extent of the radivactive fall-out due. to soil debris.
The particle size distribution of the soil debris uhich is sucked-“up:
into the mushroom cloud is known; therefore, it is possible tocorrelate the .
scaventing action vrotuced by sand with that of rain of a given intensity... 7
It may be possitle to determine the orderof ‘magnitude of the scavenging =~ an
action of rain by such a method and it 1s just this order of magnitude of
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the scavenzing action of rain that is réwuired in.order to evaluate some of.
the presently available reports dealing with the efects,‘of rain on radiomactive fall—out from. theatonic cloud. wet
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It. SCAVENG DG ACTION OF PAIN AS REPORTED “DURING‘ATOMIC.‘TEST “OPERATIONS.
"During both SANDSTONE (1) and TUMBLER/SNAPPER 2). Atonte Test‘Opsrations-”
it was reported, that’ rainfall increased the_radioactive fall-out, ‘but this:La?
increase in fall-out vas never greater, thin10 to158, of the. normal fall-outes=:
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SCAVENGING acrTow OF sor, DEBRIS piRIG TOMER‘ors‘or vs TEST OPERATIONS.*
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During TUMBIER/SYAPPER Test Operations: very Little fall-out of radio=~-
activity occurred for air ¢rops, but the fall-out was significent during all 2
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four tower shots (290 ft. towers, 12 to 15 KT bombs). ,As a matter of fact, ..>5
anproxinstely 5 to 30% of the total Ag] hour activity. of the atomic bombs. ro 4
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detonated from towers vere deposited in an area of fron, 10 to 200 miles Prom= +:
grount zero. In Figures 1, 2, 3 and 4 thisfall-out is“plotted_ in the form:
of infinity dose lines. The data used in ‘plotting the infinity @ose lines.ae
contained in the t/s Radiolopical Defense anual which is nowin the process*
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of being publisted. The inclosed tables ‘give more , detailed information with”
reference to the last four tower shots ofT/S_ test‘operations and the radio-’ 4
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_ active fall-out resulting from them. ‘There is_no doubt that the great increase =
in radioactive fall-out for the tower shots eas convzred to theair. drops is < 8,
due to the fact that a considerable amount of sand and” soil debris wes sucked'.+&
up into the mushroom of the tower shots, but practically no mixing occurred” >"
‘for the air drops which were exploited from 1000 to 3000 ft. above terrain. Bt
B. A stuiy of the inclosed figures and the tabulated ‘date, ‘shows that theres
was a distinct area of maximum fall-out for each tover shot. The distance of 14%
this maxima fall-out area vas pronortional 1to. the average> horizontalwind “speed: