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411045
Long Term Activity Estimates
For The Northern Marshall Islands
This paper provides preliminary upper-bound estimates of the
residual gamma activity on the northern Marshall Islands due to U.S.
atmospheric testing at Bikini.
These estimates are intended to be
indicative of the activity to be determined by up-coming deteiled
Surveys.
Estimates are also provided for islands in the Enewetak atol}
and compared with the 1972 survey.
Finally, an analysis of wind pro-
files and fallout patterns is presented which serves to delineate those
northern Marshall islands which were uncontaminatec by fallout frov
the Bikini tests.
1.
BEST COPY AVAILABLE
_ APPROACH
After 20 years or so, the principal fission products of interest
are 790 and csi3? whose characteristics are summarized below.
Isotopes
sro
cs?37
Curies/kt of
Fraction of
Fission at H+]
Total Curies
210
2.1x1077
- 329
6.1x1077
Half Life
_ Decay Mode
29y
B only
30y
g (109%) and
¥ (932)
The fractional contribution of Cs 137 to the one-hour dose rate
is not the same as the fraction of total Curies at one hour since the
cs}3? y energy is lower than that average energy for all fission products (.66 MeV vs. 2 MeV).
This results in a roentgen response for
cs?3’ that is 0.41 times that for the inventory taken as a whole. At
some time after burst, when cs3? fs the only remaining fission product
yeemitter, the dose rate is given by
DOE ARCHIVES
D(T) = (2 hr) [6.1x107” x 0.423 (0.5)"/%°
where T is in years. Note that beta activity is not being considered
here on the presumption that the survey techniques distinguish between
Enclosure
(2)
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