SECTION |
INTRODUCTION AND SUMMARY
During the period 1-2 March 1954, twenty-eight Army and Air Force personnel
stationed at Rongerik Atoll in the Marshall Islands were exposed to radioactive fallout
from Shot Bravo of Operation CASTLE. The purpose of this report is to determine the
whole body gamma radiation dose received by these personnel prior to their evacuation
from the atoll, plus their organ dose commitments from internal emitters.
The external gamma radiation dose (i.e., dose equivalent) is reconstructed as
follows. The radiological environment resulting from Shot Bravo fallout is determined
from time-of-arrival data on Rongerik, modeled deposition, measured decay rates, and
a
later
reading on
Rongerik.
Personnel
activity
scenarios
are
considered
in
conjunction with radiation shielding factors to arrive at film badge doses on an
individual basis. Although film badge readings are available, they relate inadequately
to personnel dose.
Readings that reflect well-specified exposures indicate good
agreement with corresponding calculated doses. A small, but systematic, difference
suggests an adjustment to the calculated personnel doses, which are in the vicinity of
40 rem.
Organ-specific 50-year dose commitments (i.e., committed dose equivalent)
resulting
from
the
large-particle
radionuclides are calculated.
inhalation
and
ingestion
of
Bravo
fallout
Intake of iodine-131 is determined from the body
metabolism of iodine that led to a measured activity of I-131 in a pooled urine sample
taken 17 days after Bravo.
The radionuclide inventory for the time of intake is
normalized to the level. of I-131
activity, thereby indicating the full intake of
radioactivity. Large-particle inhalation dose conversion factors for each radionuclide
are developed for calculation of internal dose commitments to each organ.
The
calculated thyroid dose is 190 rem, and dose to the intestines is as great as 76 rem.
Other organ doses do not add significantly to the external gamma dose.