eo
_ DRAFT
The instruments were calibrated with a 137Cs point source on the primary
calibration range of the National Environmental Research Center, Las Vegas,
Nevada.
While the response of this instrument is energy-dependent, our
experience at Enewetak showed that this was not a serious limitation
because of the dominance of 13’Cs in the radiation background on the Atoll.
We also utilized the Reuter-Stokes high pressure ionization chamber.
The
current produced by the radiation induced ionization within the chamber is
measured by a sensitive electrometer with digital readout.
The instrument
exhibits a flat energy response over all gamma-ray energies of interest to
this survey.
It is capable of measuring exposure. rates from about 1 upR/hr
to 200 upR/hr with an accuracy of about 5%.
Thus, the results derived from
this instrument were chosen as a reference to which measurements obtained
by other techniques were compared.
Measurements of the exposure rate at 1 m above the ground were made
with the Nal scintillator at approximately 2500 locations on a 30-m
rectangular grid on Bikini Island and at about 120 locations on a 120-m
grid on Eneu Island.
The jonization chamber was primarily used for
measurements within the central section of Bikini Island with additional
measurements made at selected areas.
Thus, from this program a very
comprehensive picture of the gamma-ray exposure rates is available for
both islands.
Thermoluminescent dosimeters (TLD's) were also employed
to supply a third technique for evaluating the external dose.
A complete
report on the external gamma measurements and resulting dose assessment
has been published (2).
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