SECTION 1
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 gamma radiation dose 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 indicates an adjustment to the
calculated personnel doses, which are in the vicinity of 40 rem.
Organ-specific 50-year dose commitments resulting from
the large-particle
inhalation and ingestion of Bravo fallout radionuclides are calculated.
Intake of
iodine-131 is determined from the body metabolism of iodine that led to a measured
activity of 1-131 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 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 intestinal dose is as great as
76 rem. Other organ doses do not add significantly to the external gamma dose.