155 Eu,
and
pCi/g and 0.06 pCi/g.
Tam were expected to
As expected,
contribute at most a few percent
the profile samples showed a wide
to the total exposure rates.
range of activity distributions as
This
was confirmed by Ge(Li) gamma
a function of depth on the two
spectral analyses of several
islands.
hundred soil samples collected on
are difficult to make, the activities
both islands during the June 1975
on Bikini Island usually decreased
survey.
with depth in the first few centi-
The detailed results of
Even though generalizations
the soil survey will be published
meters with a relaxation length of
in a subsequent report.
about 5 cm (the depth at which the
In summary,
the soil survey included the random
activity is et, or 37% of the surface
collection of two types of soil
activity).
samples on each island:
activities were relatively low and
and profile.
surface
On Eneu Island, the
uniform throughout the full range
Each surface sample
consisted of two 15-cm-deep cores.
of depths sampled.
Profile samples were obtained from
data in conjunction with the data of
the sidewall of a trench dug for
Beck et al.,* we estimated the
the purpose.
average 137 Cs and 60 Co contributions
On Bikini Island the
‘median 13766 and 690, activities
Using these
to the total gamma-ray exposure rates
exhibited by the 15-cm-deep core
over the two islands to be 94% and
samples were 41 pCi/g and 0.74 pCi/g,
6%, respectively.
respectively; while on Eneu Island,
were assumed to be valid over the
the corresponding values were 2.5
remaining islands of the atoll.
These percentages
External Dose Estimation
In addition to the gamma-ray
reasonable selection of possible
exposure rates, we need to consider
conditions that would cover the range
the expected living patterns of the
of doses that could be received by
future inhabitants in order to
any sizeable segment of the popula-
evaluate the external dose problem.
tion.
Of course, many uncertainties are
experiences during the Enewetak
1
survey as well as on discussions
inherent in the prediction of
future living patterns.
_
However,
These were based upon our
with personnel from the Trust
the following cases, shown in
Territory of the Pacific Islands.
Table 1, have been chosen as a
Suggestions have also been solicited
-14-