\
lectremeter “ith a digitai veadout.
(b
fikint
The
instrument exnibits a
Zlat
This sampling program was
enere-
integrated vith previous troerams to
of
avoid duplicarion or erfor
t: this
survev.
It
is
th
capable of measuring exposure rates
rom approximately 1 to 200 UR/hr with
an accuracy cz about 5%.
Thus,
the
actual numb r or
o
interest
samples
ia
response over 2il gamma-ray energies
~_s
~ne
<sken end
their specific collection sites vere
determined bv expected activity leveis,
data from this instrument were used a8
home-construction plans,
a reference =sr measurements by other
dlans, and the number of locations of
techniques.
recent soil samples
Exposure rates at 1 m above the
agricuitural
collected bv other
programs.
ground were measured with the Nal
scintillator it approximately -500
Methods and Measurements
locations on 4 30-m rectanguiar gric
Two types of soil sampies were col-
on Bikini Island and at about 120
lected for analysis:
locations on a 120-m grid on Eneu
suriface-core sample of 60-cm- area,
Island.
and a profile collection based upon
The ionization chamber was
a 15-cm deep,
primarily used for measurements within
sidewall sampling in a trench in which
the central section of Bikini Island
samples of 100-em? area were collected
with additional measurements made arc
at 15-cm-depth increments to a depth
selected areas.
of 90 cm.
Thus,
from this pro-
To plan the survey, 3ikini
gram a very comprehensive picture of
Island was divided into the north,
the gamma-ray exposure rates at both
central,
islands is available.
respective second baseline roads.
cent dosimeters
Thermolumines-
(TLDs) provided a
and south sections along the
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.”
Soil Survey
The soil sampling program was
Note that a major fraction of
the surface samples were collected
within the central section of Bikini
designed to identify the primary
Island.
This was because or 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