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electrometer with a digital readout.
Bikini and Eneu Islands of the Bikini
The instrument exhibits a flat energy
Atoll.
response over all gamma-ray energies
integrated with previous programs to
of interest to this survey.
avoid duplication of effort.
It is
This sampling program was
The
capable of measuring exposure rates
actual number of samples taken and
from approximately 1 to 200 uR/hr with
theix specific collection sites were
an accuracy of about 5%.
determined by expected activity levels,
Thus, the
data from this instrument were used as
home-construction plans, agricultural
a reference for measurements by other
plans, and the number of locations of
techniques.
recent soil samples collected by other
Exposure rates at 1 m above the
programs.
ground were measured with the Nal
scintillator at approximately 2500
Methods and Measurements
locations on a 30-m rectangular grid
Two. types of soil samples were col-
on Bikini Island and at about 120
lected for analysis:
locations on a 120-m grid on Eneu
surface-core sample of 60-cm
Island.
and a profile collection based upon
The ionization chamber was
a 15-cm deep,
area,
primarily used for measurements within
sidewall sampling in a trench in which
the central section of Bikini Island
samples of 100-cm* area were collected
with additional measurements made at
at 15-cm-depth increments to a depth
selected areas.
of 90 cm.
Thus, from this pro-
gram a very comprehensive picture of
To plan the survey, Bikini
Island was divided into the north,
the gamma-ray exposure rates at both
central, and south sections along the
islands is available.
respective second baseline roads.
Thermolumines-
cent dosimeters (TLDs) provided a
Eneu was divided by the airstrip into
third technique for evaluating the
the north and south sections.
external dose.
approximate numbers of surface and
A complete report on
The
the external gamma measurements and
profile samples collected within these
resulting dose assessment has been
sections are given in Table l.
published.”
Note that a major fraction of
Soil Survey
the surface samples were collected
The soil sampling program was
designed to identify the primary
within the central section of Bikini
’ Island.
This was because of the
radionuclides contributing to the
higher and more variable gamma-
external gamma exposure and to deter-
exposure rates in this area and the
mine the geographical distribution of
fact that a major fraction of the
these radionuclides in the soil on
returning Bikinians are likely
bd
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