EVENT AND
1.2
DESCRIPTION OF EXPOSED
GROUPS
3D
carried out, nor was its operating condition
Whole Body Gamma Doses
known to be satisfactory under the emergency
condition prevailing at the time of use. For
Tur EstimatTep Vauves of external dose given
in Table 1.1 were calculated from readings of
radiation field survey instruments.* Averages
of a numberof dose rate measurements on each
island at a given time were used. The readIngs were taken in air, approximately three
feet above ground, several days after the inhab-
these reasons the later readings, which were
higher than the early survey by an average of
50 percent when corrected to the same times,
were used in computing the doses listed. The
instruments used for the later measurements
were calibrated just prior to the surveys.
30
~secee
ORIGINAL SOURCE SPECTRUM
ame
INFINITE PLANE,3 IN AIR
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ENERGY (KEV)
Ficure 1.2—-Distribution of inherent energies of gamma radiation from mized
fission products, and histogram of degraded energies produced by Compton
scattering at level of infinite plane 3 feet in air above uniformly-distributed
fission products field,
itants were evacuated. Before this time, adequate surveys with well calibrated instruments
had not been possible, although readings had
been taken with a single survey meter at the
time of evacuation. However, preliminary
calibration of this instrument had not been
Po
C3
a
*Army Navy catalop AN/PDR-39,
1.21
Characteristics of the Gamma Radiation
The fallout material, when deposited on the
ground, formed a large planar source of radiation. The energy distribution of the radiation
reaching an exposed individual was influenced
by its passage throughthe intervening air. A
knowledge of the energy spectrum of the ra-