Ronge lap were observed at Utirik for the 90Sr and 137Cs nuclides.
curve on Fiyure
16 reflects the dose equivalent,
The lower
dose equivalent rate and body
burden which would have occurred had radioactive decay alone accounted for the
removal ot! 0°25 from the Utirik environment.
be measured for othe:
Since additional mechanisms could
nuclides at Utirik and for the 6505 nuclide on a nearby
atoll, th: upper cur ‘e was chosen as the most likely body burden history for
adults post return tu Utirik Atoll.
Figure 17 indi: ates the Utirik adult mean total body dose equivalent rate
for each nuclide.
Au obvious difference relative to the Rongelap history
exists, 6520 not 137 was the major nuclide contributing to the dose equivalent
rate.
This was due to the Utirik population returning 4 months after the ini-
tial contaminating event, and the Rongelap population returning after 3 years.
The age of the fallout had a dramatic influence on the importance of each nuclide contributing to the internal dose equivalent.
In fact 606, and 6525
played major roles during the first 3 years, a time interval that corresponded
to the period during which field whole body counting facilities were being
developed at Brookhaven National Laboratory and when medical examinations for
people on Utirik Atoll were not done.
Additionally, pooled and/or individual
radiochemical analysis of urine was not performed during this period.
The
impact of 6520 and 60, was such that even if the least conservative dietary
rate constant (K,,=0) was used for Zn, the dose equivalent rate for the average
adult was in excess of Federal Radiation Council Guidelines for the first
2 years following the return to Utirik.
18