ore
* Stn ey
aa te
place after the first 1 or 2 years after deposition®’”.
in 1967 the scil samples indicate most of the activity is
still in the first inch of soil we can probably discount
Since
weathering as an important factor in lowering the exposure
rates on Bikini island.
The levels on Nam and on some of
the other larger complexes, where "ao and other relatively
short-lived isotopes are the major contributors, although
at present in general higher on the average than Bikini
Island, will decrease more rapidly and in a few *°co halflives will probably exhibit leveis generally much lower than
Bikini Island.
Since the scil on some of these islands
contain very little organic material, weathering may result
in an even more rapid decrease in exposure rates.
Thus, the
levels on Bikini Island itself are likely to be the limiting
factor in assessing the long term hazards to any future
population living cn the atoll and centered on Bikini Island.
The consistency of the various portable detector,
ionization chamber, TLD, and spectrometer results indicate
we have obtained a reliable and comprehensive picture of the
external gamma radiation environment or the atoll.
The soil
sample results, although nct as consistent with the other
data as could be desired due to the problems of obtaining
representative samples in a very irhomogenecus distribution,
¢
aan,
do nevertheless substantiate the field spectrometric
predictions as tc the relative importance of various emitters
in the soil.
The importance of the field spectrometric
measurements in expanding and increasing the information of
the survey meter readings again illustrates the utility of
such a system in undertaking an environmental radiation
survey.
Comparabie data on the compcsition of the radiation
field could only have been cbhtained by analyzing hundreds
of carefully obtained soil samples. if at all.
The data in this report should form a solid basis for
estimating external dose to a returning population as a
function of time after return, assuming with the aid of the
survey team's anthropologist various realistic models for
their living conditions, areas of habitation, and daily
habits.
~ AQ