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TROPOSPHERIC DEBRIS (ASSUMING 100% FISSION YIELD), KT
642
10!
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Lbit ptriil bp pid te ih pp
100
5001
5 10
50 100
+— KILOTONS —»+———— MEGATONS ——>
TOTAL YIELD
Fig. 7—Amount of debris (kilotons equivalent) initially injected in the
troposphere as a function of total yield for air bursts in a tropical
atmos phere.
is quite similar with a maximum tropospheric contamination of about
1.5 Mt for yields between 2 and 3 Mt, all fission. This curve also de-
creases rapidly and then levels off at about 12 kt of tropospheric debris
for yields between 15 and 100 Mt. It should be recalled here that these
curves are based on the activity—height curve given in Fig. 5 and are
Subject to the same uncertainties.. For thermonuclear devices the
amount in the troposphere should be multiplied by the fission fraction
of the device.
Dominic | Debris in the Troposphere
With the use of the estimated tropospheric fraction and the fission
yield for the individual Christmas Island detonations, it is estimated
that about one-third of the total radioactivity initially stabilized in the
troposphere. Since a half-residence time of one month is generally
accepted for tropospheric debris, !” about one-sixth of the total activity
might be expected to be deposited at the surface, mostly in tropical
latitudes, within a month after the conclusion ofthis test series. A rough
integration!! of the activity found in the AEC Health and Safety Labora-
tory monthly fallout-deposition collections indicated that only about half
this amount was deposited in the latitude band from 30°N to 30°S