407587
Long Term Activity Estimates
For The Northern Marshall Islands
This paper provides preliminary upper-bound estimat s of the
residual gamma activity on the northern Marshall Islands du
to U.S.
atmospheric testing at Bikini.
to be
These estimates are intende
indicative of the activity to be determined by up-comine de éiled
Surveys.
Estimates are also provided for islands in the En wetek ato}
and compared with the 1972 survey.
Finally, an analysis of Wind pro-
files and fallout patterns is presented which serves to del neate those
northern Marshall islands which were uncontaminatec by felldut froz
the Bikini tests.
I.
BEST COPY AVAILABLE
_ APPROACH
After 20 yeers or so, the principal fission product
of interest
are 5790 and cs}?? whose Characteristics are summarized beldy.
Isotope
gr?
cs9?
Curies/kt of
Fission et Ht]
Fraction of
Total Curies
110
- 320
2.1x1077
6.1x107”
Half Life
_ Decay Mode
29y
30y
B only
B(100z) and
¥ (93%)
dose rate
The fractional contribution of cst9? to the one-houy
is not the same as the fraction of total Curies at one hour[since the
cs 23?
that average energy for all fi sion pro-
y energy is lower than
ducts (.66 MeV vs. 2 MeV). This results in a roentgen respgnse for
cs}9? that is 0.41 times that for the inventory taken as a whole. At
some time after burst, when cs)9? is the only remaining fisgion product
syeemitter, the dose rate is given by
b(t) = B(1 hr) [6.1x2077 x 0.41) (0.57/20
where T is in years.
DDE ARCHIVES
Note that beta activity is not being
gonsidered
here on the presumption that the survey techniques distinguish between
Enclosure
(4)
—_
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