a> the D+ 1 Survey does not indicate comp rable dose rates. The aircraft encountered active
fallout and became contaminated. A replacement aircraft was flown to the survey area. This
also becan.c contaminated.
At no time was the level in the aircraft allowed to exceed 20 mr/hr.
Both aircraft on the D + 1 flights (Figure 3.11) were also lightly contaminated.
Active fallout
was encountered 100 miles northwest of Bikini at H + 30 hours. The northwest sector was
closed, as far as aerial surveys on D+ 1 were concerned. As indicated on the chart, it was
not possible to close the isodose plot at that time.
The pruject had four aircraft to choose from for the D + 2 flight, all reading a background of
approximately 0.1 mr/hr inside the detector shielding.
The survey for this day could not detect
any surface contamination reading above a minimumdetectable limit of 0.25 mr/hr at 3 feet
from the surface. Table 3.4 summarizes the fatlout distribution.
TABLE 3.4.
SUMMARY OF FALLOUT DISTRIBU LION, FLATHEAD
Isodose
Area
Difference Area
Average
!
!
t
mr/hr
mi2
mi?
mr/hr
i
0.368
0.148
0.074
0.037
‘
i
}
=:
{
|
D1
0.2
0.1
0.05
0.025
383
908
3,350
11,000*
383
525
2,442
7,650*
t
=
noe
* Based on estiniated position of isodose line.
The EOB is roughly estimated and may not be representative of the actual extent of the contamination.
3.3.4 Shot Mohawk. A survey of the islands of Eniwetok Atoll was flownon D+1. The island
readings are shown in Figure 3.12. The readings are referred to 3 feet above the surface of the
islands by a factor of 5.8 for the 300-foot flight altitude (Figure 1.2). Sites Fred and Elmer were
excluded from the survey pattern, because a 300-foot flight altitude would have interfered with
the air traffic in the vicinity. The open-sea aerial survey could find no detectable contamination
in the area searched (Figure 3.13).
3.3.5 Shot Navajo.
A background survey was made on D—1 day to determine if the hot inten-
sities, reportedby Project 2.62, adjacent to the reef after Shot Flathead, could have come from
contaminated water crossing the reef. This flight (Figure 3.14) subsequently became a D—3
survey because of postponement of the shot. The next flight (Figure 3.15) became the D-2 survey, again because of a postponement. The aircraft flight, on the day which would have resulted
ina D—1 survey, was not completed because of malfunction.
The background surveys were coordinated with a Project 2.62 ship survey.
Because the
shape and position of the contaminated area varied from day to day, it is possible that the variation may have been a function of the surface winds. An outline of the area, based on the ship
data has been included as Figure 3.16. The agreement between these plots appears good, in
view of the 12-hour displacement between the ship and aerial survey.
The D-day survey (Figure 3.17) located the estimated upwind boundary. On D+1, the flights
covered an area of 10,000 mi’ but did not close the 0.025 mr/hr isodose line in the northwest
sector (Figure 3.18).
The D+2 chart (Figure 3.19) shows that this isodose extended farther
than estimated on the previous days. The narrow 1.25 mr/hr line extending to the west of the
atoll had disappeared. Reef readings have been included in this chart.
The summary of the fallout distribution (Table 3.5) indicates considerable instability in the
contaminated area during the aerial-survey operations. As experienced after the previous water
35