a

of the area to determine the degree of uniformity of the
exposure rate.
The exposure rates obtained were:
South side
59.9 ur/hr, East side 68.7 ur/hr, North side 76.8 ur/hr, and
West side 83.0 ur/hr.
The corresponding field spectra
indicated the differences in exposure rates were due to
‘

.

137

60

s

.

‘

.differences in
Cs,
Co, and 18E oh contributions, rather
than to any new contributors, with the percentage contribu-

tions of each isotope remaining fairly constant.
These
local variations in the isotope distribution pattern seemed
to be typical of many areas on Bikini and again indicate the
difficulty in obtaining a soil sample representative of the

area as a whole.
However, the excellent agreement of the
sum of the field spectrometric exposure rate estimates with

the ion chamber measurements and the agreement of the two

independent calculations of the percentage of total exposure

rate due to each isotope verifies that the field spectrometer
averages out most of these variations.
Four HASL TLD dosimeters were exposed at this site for
about 8 days duration.
The average exposure rates were 56

ur/hr for two placed in the center, 78 wr/hr for one placed
on the northeast side of the clearing, and 65 ur/hr for the
fourth which was situated on the southwest side of the
clearing.
These data agree quite well with the ionization
chamber and spectrometer total exposure rate estimates,
tabulated above.
A study of the Ge(Li) spectrum of the soil obtained
from this site indicated, as was the case for the soils
obtained on the 0 Transect, the presence in small amounts

of *52nu, *®’ pu, and ***am in addition to **’cs, *#°sb, anda
Co.

Summary of Exposure Rates on Bikini Island - The total gammaray exposure rates on Bikini Island ranged from 10 - 120

meen Mg

ur/hr.
In general, the areas close to shore were 20 - 40
ur/hr and the island center was 50 - 80 ur/hr while scattered
hot spots exhibited levels up to 120 ur/hr.
Cosmic rays
result in an additional exposure rate of ~3.4 ur/hr at all
locations.

The primary contributor to these gamma-ray exposure

rates was *°’cs, with °°co and **®®sSb the only other signifi-

cant contributors.

Select target paragraph3