410861
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
_morthern Marshal] islands which were uncontaminated by fallout froz
the Bikini tests.
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APPROACH
1.
After 20 years or so, the principal fission procucts of interest
are 590 and cs 3? whose characteristics are summarized below.
Isotope
gr20
cs 29?
Curies/kt of
Fission at H+]
110
- 329
Fraction of
Total Curies
2.1x107”
6.1x1077
Half Life
_ Decay Mode
29y
30y
B only
2(100%) and
¥ (932)
“ The fractional contribution of Cs 137 to the one-hour dose rate
is mot the same as the fraction of total Curies at one hour since the
cs}9? 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??? that ts 0.4) times that for the inventory taken as a whole. At
some time after burst, when cs}3? fis the only remaining fission product
voemitter, the dose rate is given by
DOE ARCHIVES
D(T) = O(1 hr) [6.1x107” x 0.42) (0.5)*/3°
Note that beta activity is not being considered
here on the presumption that the survey techniques distinguish between
where T is in years.
Enclosure
(2)
2°