”

(EES ORB OBES!

Table 1.

Number of soil sample locations on each island

(continued).

No. of Sample Locations
Surface

(0-15 cm)
Eneu

North of airstrip
South of airstrip

TOTAL

-

60
40
350

Profiles

(0-90 cm)
2
2

12 (6 samples
each)

The exact soil sampling locations will actually be determined by a
random selection process to obtain statistically meaningful and unbiased
results. Special samoles will also be collected within ‘hot spot” areas
or other areas of specialized interest. The samples will be placed in
plastic bags with appropriate identification tags and readied for shipment to LLL, where they will undergo preprocessing and gamma-spectral

analysis. It is anticipated that analyses for other radionuclides of
interest, such as plutonium-239 and strontium-90, will be performed at a

contractor laboratory.

Purpose:

Gamma-Exposure Rate Survey

The gamma-ray exposure measurements program conducted on the ground
is designed to provide detailed examination of the geographical variability of the exposure rates on Bikini and Eneu Islands, and to provide
overall verification of exposure rate measurements mace during previous
visits.

Baae

Methods and Measurements

openRE

The program utilizes the Baird-Atomic scintillation detector which consists of a 2.5-cm-diam x 3.9-cm-long Nal crystal with ratemeter readout.
The instrument is calibrated with a !3’Cs 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 }37Cs in the radiation background on the Atoll.
We will also utilize the Reuter-Stokes high pressure ionization chamber.
The current produced by the radiation induced ionization within the chamber is measured by a sensititive 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 pR/hr to 200 yS/hr with an accuracy of about 5%. Thus, the
results derived from this instrument may be chosen as a reference to which
measurments obtained by other techniques can be compared.

DOE ARCHIVES

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