Appendix Il
DOSE ASSESSMENT*
A.
Early Radiation**
1.
Source
The ionizing radiation exposure of the Marshallese was due entirely to
fallout, since the detonation site was too far away for thermal, blast, or di-
rect irradiation effects.
(In contrast, direct effects were responsible for
all the injuries from the atomic bombs in Hiroshima and Nagasaki, with little
The fireball from the 1954 Bravo device, detonated from a
or no fallout.)
tower, touched the surface of the earth at Bikini, and large amounts of mate-
rial were drawn up and mixed with fission products in the bomb cloud.
Because
of an unpredicted shift in the winds in the upper atmosphere, fallout was
deposited in a cigar-shaped area 20 to 40 miles wide extending “200 miles to
the east of Bikini (see Figure 1 in the text).
The radioactivity was due to
fission products and some neutron-induced radionuclides; little Fissile material was noted.
The radiation was therefore almost entirely from gamma and
beta rays of varying energy from numerous neutron-rich radionuclides.
The
time after detonation when fallout began was estimated as 4 to 6 hr at
Rongelap, “7 hr at Rongerik, and 22 hr at Utirik, and the fallout duration as
12 hr, with most of the dose delivered early in that period.
fallout exposure data on the atolls.
Table 1.
Table 1 shows
Estimated gamma exposure (measurements in air).
Instrument
No.*
Atoll
people
Rongelap
A1ilingnae
Rongerik
Utirik
Approx.
time
Time of
readings
fallout began
evacuation
64
H+4 to 6 hr
375, H+7 days
18
H+4 to 6 hr
H+50 hr (16 people)
H+51 hr (48 people)
H+28.5 hr (8 men)
H+34 hr (20 men)
Started at H+55 hr
280, H+9 days
78
40, H+8 days
14
28
157
H+6.8 hr
H+22 hr
H+58 hr
(mR/hr)
Est.
100,
H+9 days
Y
exposure
CR)
175
69
*Does not include people exposed in utero.
“Dr. S.H. Cohn (Medical Department, BNL) and Messrs. E.T. Lessard, N.A.
Greenhouse, and R.P. Miltenberger and Dr. J. Naidu (Safety and Environmental
Protection Division, BNL) assisted with this Appendix.
**A reevaluation of the early whole-body and internal organ doses is in progress at Brookhaven National Laboratory.
Incomplete results give some indication that the previously estimated thyroid doses may be too low.
Since the
‘results are preliminary, they are not included in this report.
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