The agreement between spectrometric and ionization chamber
total exposure rates is least satisfactory for Locations 1
and 2 on this island than fer other lccaticns surveyed on
Bikini and Eneu.
This is probably due to the non-uniformity
of distribution of radioactive materials on Nam.
Near both
Locations i and 2. highly active pieces of metal scrap were
located in the soil within a few hundred feet of the measurement sites.
Such deviations from uniform distribution
change the spectrometer calibration slightly, though the
exposure rate estimates from the tctal absorption peaks of
the spectrum still represent close to average values for a
large area about the detection point.
Measurements with the
ionization chamber cver a larger area would probably have
resulted in a better average total exposure rate estimate.
A soil sample was taken at Location 2,
It is quite
probable that this sample is not representative of the area
as a whole, but the ratios of the ccncentraticns of various
major emitters present help verify the percentage exposure
rates obtained from the field spectra. The laboratory Nai(T1l)
gamma spectral analyses indicate that *“so does contribute
about 50% of the exposure rate at this site with almost all
of the remainder due to **’cs.
The Se iui} spectrum (Figure
11) indicates the presence of “*"Sb and *®°* Bu and very
slight traces cf “OB re + °° Rh, and aisc #4" am, and thus 7° pu.
Two soil samples obtained in 1964 {net at the same identical
locations) indicate that at that time °"Co was responsible
for ~70% of the total exposure rate.
This may indicate that
on islands such as Nam, where there is little organic
material in the soil and sparse vegetation, weathering may
be important and could have caused the total exposure rate
to decrease much more rapidly than half-life analyses would
predict.
Unfortunately, due to the sparsity of the data and
the observed non-uniformity of the radiaticn field, this
hypothesis cannot be verified at this time.
J.
Aomen-Iroij Complex
The Aomen-Iroij Complex consists cf the causeway connected
islands of Aomen, Lomilik, Odrik, and Iroij} from east to west
respectively.
These islands are centrally located along the