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and regional fallout contamination of islands in the
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central
Pacific basin,
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a
acific Nuclear Testing Program resulted in
as Micronesia.
ern Marsnall
in an area which is generically known
Most eof this contamination affected the North-|
Islands of eastern Micronesia,
which either served
as the actual test sites or which were in relatively close
proximity to them.
Since all of the Marshall Islands are low
coral islands or atolls, the natural radioactivity content of
their soil is among the lowest on earth;
and their natural
radiation environment is dominated by the contribution of cosIn contrast,
the high islands of the Caroline groups,
x
mic rays.
to the west or the Marshalis, are characterized by volcanic
+
soils having a significant complement of radionuclides in the
uranium and thorium chains.
Several field trips by SgEP
Division personnel to Micronesia between 1975 and 1980 have
afforded opportunities toa study the natural radiation environments of the coral atolls of the Marshalls and several high
islands
in the Carolines;
and to evaluate the contributions of
fallout fission and activation products to the inventories
of soil radioactivity in these locations.
The analytical methods
employed included in situ gamma spectrometry and exposure rate
measurements with pressurized ion chamber survey instruments.
These measurments were supplemented by Jaboratory analyses of
soil samples.
The rasults of these studies have indicated that
Significant contributicns from radioactive fallout can be evaluated in situ with relative ease on coral
islands.
In contrast,
the higher natural radioactivity content of high island soils,