minimize external exposure,
ple (see acknowledgment) and the sup-
a survey
of Bikini Atoll was proposed.
Initial
port of the ERDA Research Vessel,
plans. called for aerial surveys to
Liktanur, from June 16 through June 24,
determine external gamma levels on all
1975.
islands in the atoll along with ground
surveys using scintillation counters
The basic plans for the 1975 Bikini
survey are outlined below.
and thermoluminescent dosimeters
(TLD).
SURVEY PROGRAM OF BIKINI SOIL AND
GAMMA EXPOSURE RATE
Emphasis was to be placed on
Bikini and Eneu Islands, the prime
residence islands.
In addition, there
was to be a rather large scale effort
Survey of Gamma-Exposure Rate
The program for the measurement of
to sample the soil and vegetation to
gamma-ray exposure rates conducted on
evaluate the potential dose via the
the ground was designed to examine in
terrestrial pathway.
detail the geographical variability of
It was felt that
this was an especially important goal
the exposure rates on Bikini and Eneu
in view of the significance of the
Islands,
contribution of the food chain to the
measured during previous visits.
and verify exposure-rates
total dose estimated at Enewetak
Methods and Measurements
Atol1.+
For a number of reasons, the scale
A Baird-Atomic scintillation detec-
of the program had to be reduced from
tor, which consists of a 2.5-cm-diam
that originally planned.
x 3.9-cm-long NaI crystal with a
Manpower and
Support were reduced, and the aerial
ratemeter readout was used.
Survey was temporally deferred, leaving
instrument was calibrated with a 137¢6
the entire program of measuring the
point source in the primary calibra-
external dose levels on Bikini and
tion range of the National Environmen-
Eneu Islands to be accomplished by
tal Research Center, Las Vegas, Nevada.
ground crews.”
While the response of this instrument
The emphasis of this
reduced effort was toward the external
is energy-dependent,
The
our experience at
gamma measurements on Bikini and Eneu
Enewetak showed that this was not a
Islands.
serious limitation because of the
Although the sampling of the
food chain pathways was less extensive
dominance of 13764 in the radiation
than we had hoped, we maintained a
background on the atoll.
smaller scale program designed to help
a Reuter-Stokes high pressure ioniza-
assess the potential dose via inges-
tion chamber.
tion pathways.
the radiation-induced ionization within
The 1975 Bikini survey
was conducted with the help of 20 peo-
5009953 —
~
We also used
The current produced by
the chamber is measured by a sensitive