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excess of 100 uR/hr were found.
(Surface radiation readings were made at
3 feet.) No radiation debris at any levels of activity was buried on the
islands of Bikini, Eneu, or Aerokoj.
The exterior of several bunkers, located on the northern complex
(Iroij, Odrik, Lomilik, and Aomen) and Nam, exhibited contact levels of
radiation up to 7,000 uR/hr, combined beta and gamma.
The net gamma
levels were 200 uR/hr maximum.
The levels inside the bunkers were less
than 10 uR/hr.
Natural background in the U.S. is about 20 uR/hr.
Since
the potential for personnel exposure was negligible and the bunkers were
desired as typhoon shelters and storage buildings by the natives, the
larger bunkers were left intact.
2.3
BIKINI ISLAND
The island was prepared for agricultural redevelopment by cutting
parallel strips through the vegetation along the length of the island.
The vegetative cover was knocked down and left in place to provide additional organic matter for the soil.
The strips were surveyed and gamma
radiation levels recorded at 250-foot intervals along their length.
Figure 2 illustrates the variation in these levels by depicting the
range and average of gamma radiation measurements taken at three feet
above the ground for areas consisting of approximately four strips.
Although a large amount of debris was found on Bikini (from the
testing program and World War II), the only material found to be radio-
active was a pile of roofing paper scraps contaminated primarily with
137Cs located northwest of center on the lagoon side of the island.
This material, which showed a contact reading of approximately 200 uR/hr,
was loaded into 55-gallon drums and disposed of in one of the disposal
sites in the ocean south of Eneu.
The measured exposure rates were 10 uR/hr or less along the beaches
and ranged from 20-120 uR/hr inland. Soil samples taken at three locations
in 1969, having measured backgrounds of 20, 70, and 100 uR/hr, showed
137¢Cs and 60Co to be the major gamma emitting contaminants. These were
present in Cs/Co ratios of approximately 25/1, 50/1, and 30/1 respectively
for the three samples, and thus the projected exposure rate decay will
very closely approximate the decay of 137Cs.
In addition,
908r was
present in amounts ranging from 10 to 50 percent of the 137¢5 concentrations,
2.4
ENEU ISLAND
Eneu, the second largest island in the atoll and the site of the base
camp for the clean-up operation, was found to have external radiation
levels considerably lower than Bikini (Figure 3).
Although an exposure
rate of 50 uR/hr was obtained at one depressed location during the early
stages of clean-up, filling of this "borrow pit" area reduced the level
to approximately 10 uR/hr.
than 10 to 20 uR/hr.
The exposure rate generally ranged from less
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