SWRHL-lllr
REPORT OF THE RADIOLOGICAL CLEAN-UP
OF BIKINI ATOLL
by
Allan E. Smith and William E. Moore
Office of Dose Assessment & Systems Analysis
Western Environmental Research Laboratory
ENVIRONMENTAL PROTECTION AGENCY
Published January 1972
This study performed under a Memorandum of
Understanding (No. SF 54 373)
for the
U.S. ATOMIC ENERGY COMMISSION
-------
This report was prepared as an account of work sponsored
by the United States Government. Neither the United States
nor the United States Atomic Energy Commission, nor any
of their employees, nor any of their contractors, subcon-
tractors, or their employees, makes any warranty, express
or implied, or assumes any legal liability or responsibility
for the accuracy, completeness or usefulness of any infor-
mation, apparatus, product or process disclosed, or repre-
sents that its use would not infringe privately-owned rights.
Available from the National Technical Information Service,
U. S. Department of Commerce
Springfield, Va. 22151
Price: paper copy $3.00; microfiche $.95.
Ub8
-------
SWRHL-lllr
REPORT OF THE RADIOLOGICAL CLEAN-UP
OF BIKINI ATOLL
by
Allan E. Smith and William E. Moore
Office of Dose Assessment & Systems Analysis
Western Environmental Research Laboratory
ENVIRONMENTAL PROTECTION AGENCY
Published January 1972
This study performed under a Memorandum of
Understanding (No. SF 54 373)
for the
U.S. ATOMIC ENERGY COMMISSION
-------
ABSTRACT
As a result of a decision by President Johnson in 1968, the Atoll of
Bikini was the subject of an intensive clean-up effort in 1969 by a
joint AEC-DASA task force. The task force was responsible for rehabil-
itating the islands of Bikini and Eneu in preparation for the resettle-
ment of the Bikini an people to their home islands. Radiological Safety
Advisors were provided by the Western Environmental Research Laboratory,
Environmental Protection Agency. Objectives of the clean-up effort were:
removal of all debris from the islands; determination of existing radiation
levels on each island; analysis of available food items for radionuclide
distribution; and clearing of vegetation from land for agricultural re-
development. Upon completion of these objectives, the islands were turned
over to the Trust Territories for the agricultural phase of the orogram.
This report describes the radiological conditions detected before, during
and following the clean-up effort.
The highest exposure-rate measured on the islands of Bikini and Eneu was
120 yR/hr. The mean exposure-rate for the proposed village area on Bikini
was 44 yR/hr. Integral dose calculations involving theoretical time periods
spent in various areas of the island and on the lagoon and considering
shielding values from coral aggregate in the village area were made. The
projected external whole body dose for a person born on Bikini in 1970 and
living there for 70 years would be less than 10 Rad.
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TABLE OF CONTENTS p
ABSTRACT i
LIST OF FIGURES ill
LIST OF TABLES iv
INTRODUCTION 1
OBJECTIVE OF CLEANUP PHASE 2
CRITERIA 3
SURVEY INFORMATION 5
CONCENTRATION - EXPOSURE RATE RELATIONSHIP 5
PROCEDURES 6
BIKINI ISLAND 7
ENEU ISLAND 9
OBOE (AEROKOJ) - TARE ( ENEMAN) COMPLEX 11
OBOE (AEROKOJ) - PETER (AEROKOJLOL) - ROGER (BIKDRIN) 11
SUGAR (LELE) -' TARE (ENEMAN) 14
UNCLE (ENIDRIK) 17
VICTOR (LUKOJ) - WILLIAM (JELETE) 20
YOKE ( ADRIKAN) - ZEBRA (OROKEN) - ALPHA (BOKAETOKTOK) -
BRAVO (BOKDROLUL) 20
CHARLIE (NAM) 25
DOG (IROIJ) - EASY (ODRIK) - FOX (LOMILIK) - GEORGE (AOMEN) 28
REEF STRUCTURES 32
DOSE ASSESSMENT 32
EXTERNAL DOSE ASSESSMENT 32
THERMOLUMINESCENT DOSIMETER PROGRAM 36
AIR SAMPLING RESULTS 37
SUMMARY AND RECOMMENDATIONS 41
REFERENCES 45
ii
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LIST OF FIGURES
FIGURE Page
1. Bikini Atoll 4
2. Bikini Island - Background Radiation Survey Results 8
3. Eneu Island - Background Radiation Survey Results 10
4. Oboe - Peter Island - Background Radiation Survey Results 12
5. Roger - Sugar - Tare Islands - Background Radiation 13
Survey Results
6. Tare Soil - Composite Decay Projection 15
7. Tare - Projected Exposure Rate Reduction 16
8. Uncle Island - Background Radiation Survey Results 18
9. Uncle - Projected Exposure Rate Reduction 19
10. Victor Island - Background Radiation Survey Results 21
11. William Island - Background Radiation Survey Results 22
12. William - Projected Exposure Rate Reduction 23
13. Alpha - Bravo - Zebra Islands - Background Radiation 24
Survey Results
14. Charlie Island - Background Radiation Survey Results 26
15. Charlie - Projected Exposure Rate Reduction 27
16. Dog - Easy Islands - Background Radiation Survey Results 29
17. Fox - George Islands - Background Radiation Survey Results 30
18. Fox - Projected Exposure Rate Reduction 31
19. Bikini Integral Dose Projection - Village Area 34
20. Bikini Integral Dose Projection - Interior 35
21. Eneu Air Sampling Locations 38
22. Bikini Air Sampling Locations 39
i i i
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LIST OF TABLES
TABLE Page
1. Mean 137Cs and 90Sr Concentration in Food from Bikini 9
Island (pCi/g wet weight)
2. Mean 137Cs and 90Sr Concentration in Food from Eneu 11
Island (pCi/g wet weight)
3. Mean 137Cs and 90Sr Concentration in Aerokoj Coconuts 14
(pCi/g wet weight)
4. Alpha Emitting Nuclides in Soil - Eneman (pCi/g air-dried 17
weight)
5. Estimate of Where Time Is Spent by Age 36
6. Projected Integral Dose for A Child Born in 1970 (Bikini 36
Island)
7. Composite 239Pu in Air Results for Bikini Island - 1970 40
8. Composite 239Pu in Air Results for Eneu Island - 1970 40
9. Daily 239Pu in Air Results for Station 1 Bikini Island - 1970 42
IV
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INTRODUCTION
During the period 1946 through 1958, the atoll of Bikini, centered
o o
about 11 36'N, 165 22'E, was the site of approximately 23 nuclear
detonations. After the atoll of Bikini was selected as a test area
the native population, numbering approximately 166, was eventually
resettled in 1948 on Kili, a single island in the southern
Marshalls, following brief stays on Rongerik and Kwajalein atolls.
Discrete test series were conducted at Bikini Atoll in 1946, 1954,
1956, and 1958 and included both fission and fusion devices. Due
to their proximity to the detonation sites, or the vagaries of the
weather, all of the islands of the atoll were contaminated to .some
extent by radioactive fallout.
In 1964 and again in 1967, radiological surveys of the atoll were con-
ducted under the auspices of the Division of Biology and Medicine of
the U. S. Atomic Energy Commission. The 1967 survey yielded an
extensive amount of data relative to the external radiation levels^ '
and the concentration of radioactive materials in the marine
(2\
environment as well as in the edible land plants and animal life. '
Following the 1967 survey, an Ad Hoc Committee was convened to evaluate
the radiological hazards of resettlement-of the Bikini Atoll. The
conclusions of the committee included the following statement: "The
exposures to radiation that would result from the repatriation of the
Bikini people do not offer a significant threat to their health and
(3)
safety."v ' On August 12, 1968, President Johnson announced the
decision to return the Bikinians to their atoll. A joint AEC-DASA
effort was initiated to eliminate any physical or radiological
hazards remaining on the atoll and to prepare the islands of Bikini
and Eneu for agricultural redevelopment. This phase of the clean-up
program was initiated in February 1969. The data provided in this
report result, for the most part, from the radiological clean-up effort
associated with this aspect of the program. Air sampling data collected
during a follow-up survey in May-June 1970 are also reported.
-------
OBJECTIVE OF CLEAN-UP PHASE
The conclusions of the Ad Hoc Committee stated that the islands of
Bikini and Eneu could be used for continuous occupancy and agricultural
development sufficient to support the returning population. The clean-up
of these islands called for:
1. the removal of all test related debris with disposal at
sea of all radioactive debris
2, stripping of the vegetation to permit planting of coconuts,
pandanus, breadfruit, etc. This was accomplished by cutting
swaths which were approximately 20 feet wide on 56-foot
centers through the vegetative cover
3. determining residual external radiation levels at each
step of the clearing and stripping operations, and
4. obtaining samples of available food items for laboratory
analysis for comparison with previously collected data.
Although permanent occupancy was to be limited to the islands of Bikini
and Eneu, the Ad Hoc Committee further concluded that "radioactive scrap
should be removed from the islands adjacent to former shot sites." Since
these islands may be used for the collection of birds, turtles, and
their eggs for human consumption, removal of radioactive debris would
make the scrap unavailable for collection by the natives.
The final objectives of the clean-up program, therefore, included the
elimination of all physical hazards and the disposal of all radioactive
scrap from each island of the atoll in addition to the specific measures
cited for Bikini and Eneu.
The Western Environmental Research Laboratory (WERL), which conducts
radiological surveillance operations in the Pacific for the AEC, was
requested to provide Radiological Safety Advisors to the AEC Project
' Manager for the clean-up effort. In addition, a comprehensive sampling
program was to be conducted of all edible varieties of food found to
be growing there. Analyses of samples were to be performed by WERL
at one or both of its two laboratories, located in Honolulu, Hawaii
and Las Vegas, Nevada.
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CRITERIA
Rather than establish firm, restrictive criteria for the removal of radio-
active artifacts, or the elimination of high background* areas from the
islands of the atoll, each situation was viewed in terms of the potential
exposure versus benefit. All debris or artifacts having little or no
useful value was removed. All scrap metal or concrete with contact
readings greater than 100 micro-Roentgen per hour (yR/hr) was treated as
radioactive waste and buried at sea. Three specific locations were
selected for this burial (Figure 1). In some cases, scrap reading less
than 100 yR/hr was buried on land together with non-radioactive debris.
This was only done on islands where areas exhibiting background levels
in excess of 100 yR/hr were found. No radioactive debris at any
level 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 levels of radioactivity
up to 7,000 yRad/hr (e + y) at contact. The net gamma levels were
200 yR/hr maximum. The levels inside the bunkers were less
than 10 yR/hr, however. 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.
Several instances of high background levels, greater than 200 yR/hr,
due to soil contamination were also encountered. It was the consensus
that attempting to reduce these levels by removing the top layer of
soil would destroy the limited agricultural capability of the area,
therefore, most such areas were left essentially undisturbed.
*The term "background" as used in this text denotes the radiation levels at
the time of survey and includes that portion resulting from testing oper-
ations as well as from natural sources. Natural background levels in this
part of the world result primarily from Cosmic rays and are Generally less
than 5 yR/hr.
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i - 07X ALPHA 'IBOKAETOKTOK) , .
I-""!" - '
, ' ZEBRA (OROKEN)
.II . . ... -- . ^,
•• "•!**. -'. .
.•*•:? V . YOKE (AORIKAN)
"
ENEu
Atoll
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SURVEY INFORMATION
Tabulations for the islands of Bikini Atoll on the following pages will
indicate:
1. the background gamma exposure rates as measured with a
Baird Atomic NE-148A scintillator calibrated against 137Cs>
2, a summary of the radiological waste removal and disposal,
3, results of sample analyses and,
4. when appropriate, projection of the background decay as a
function of time.
CONCENTRATION-EXPOSURE RATE RELATIONSHIP
In order to estimate the expected reduction in exposure rate for the
various islands as a function of time, it was necessary to develop
weighting factors for each of the gamma emitting radionuclides identified
in the analysis of soil samples.
For purposes of this report, it was assumed that the various radionuclides
were uniformly distributed by depth throughout the soil and that the only
change in relative concentrations is due to the differential decay rates.
This is obviously an oversimplification but would tend to give conservative
in)
results. The data of Crocker, Connors, and Wongv ' were used to indicate
the relative effect of each nuclide on the exposure rate. Since 102mRh
was not among the nuclides included in their tabulation, data from their
table were normalized by effective energy and number of photons per
disintegration and plotted. The exposure rate factor for 102rt1Rh
effective energy 0.62 MeV was taken from this curve and corrected
for 2.96 gamma per disintegration.* The final tabulation of the composite
exposure rate reduction was then calculated using the decay factor,
initial .concentration and exposure rate weighting factor.
*Decay scheme taken from Table of the Isotopes - Ledever, Hollander, and
Perlman.
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PROCEDURES
Gamma ray spectrum analysis and strontium analysis on all coconut, pandanus,
and arrowroot samples were performed at the WERL Pacific Operations Laboratory
in Honolulu, Hawaii. Edible portions of the samples were ground and counted
without drying on a 4- by 4-inch Nal(Tl) crystal multi-channel analyzer system.
The spectral range covered was zero to two MeV. At the concentrations of 137Cs
encountered in these samples, the counting error is approximately ten percent.
(All errors referenced in this section are 2 sigma confidence level.)
Following gamma spectrum analysis the samples were ashed and the inorganic
residue was analyzed for 90Sr. Due to the small amount of ash produced, it
was often necessary to composite samples from adjacent locations. Counting
was performed on a low background beta counter. The analytical error associ-
ated with this procedure is approximately ten percent at the levels of 90Sr
encountered.
All tritium and plutonium analyses were performed at WERL, Las Vegas, Nevada.
Tritium was determined by liquid scintillation counting of the water recovered
from coconut milk and from selected soil samples. The minimum sensitivity for
this procedure is 0.4 pCi/ml for five ml of recovered water. At this concen-
tration the error term for the 2 sigma confidence level is ± 100 percent.
Analyses of the coconut milk and soil samples indicated the concentrations
of tritium were less than the minimum detectable level.
Plutonium analyses which were performed on soil samples were by radiochemical
separation followed by pulse height analysis using a lithium-drifted silicon
detector. The analytical error is approximately ten to fifteen percent.
The analytical error associated with the results for plutonium on prefilters
is approximately ± 25% at the 2 sigma confidence level.
Unless otherwise specified each soil sample represented the top one to two
inches of a one-square-foot area at each location. Prior to plutonium analysis,
gamma ray spectrum analysis was performed to identify the most abundant radio-
nuclides and to estimate their relative contribution to the total activity.
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BIKINI ISLAND
The island of Bikini is the largest in the atoll, having an area of
about 0.6 square miles and has traditionally been the "home island"
of the Bikinians. Individual land rights extend from the lagoon to
the ocean. It is anticipated that the villaae will be rebuilt along
the lagoon shore with community buildings heina located about midway
along the length.
The island was prepared for agricultural redevelopment by cutting parallel
strips through the vegetation along the length of the island. The strios,
cut on 56-foot centers, were approximately 20 feet wide. The vegetative
cover was knocked down and left in place to provide additional organic
matter for the soil. The strips were surveyed and background gamma
radiation levels recorded at 250-foot intervals along their lenath.
Figure 2 illustrates the background variation by depicting the range
and average of radiation measurements for areas consisting of approxi-
mately four strips.
Although a large amount of debris was found on Bikini (from testing pro-
gram and World War II) with one exception, none was radioactive. One
pile of roofing paper scraps contaminated primarily with 137Cs was
located northwest of center on the lagoon side of the island. This
material, which showed a contact reading of approximately 200 yR/hr,
was loaded into 55-gallon drums and disposed of in the ocean south
of Eneu.
The measured exposure rates were 10 yR/hr or less along the beaches,
and ranged from 20-120 yR/hr inland. Soil samples taken at three
locations having measured backgrounds of 20, 70, and 100 MR/hr showed
137Cs 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 decrease will very closely approximate the decay of 137Cs. In
addition, 90Sr was present in amounts ranging from 10-50% of the 137Cs
concentrations. Both 137Cs and 90Sr are very significant contributors
to the potential internal exposure which may result from eating locally
grown food items.
*
Unless indicated as a contact measurement all exposure rate measurements
were taken at 3 feet.
7
-------
00
0
Values indicate survey results
for area (50 to 200 feet wide)
between beach and lagoon road
BIKINI ISLAND
SCALE IN FEET
10OO JOOO
3000
00--000 Range of ijrv?y C.-«u|ii in m::ic-R/hr
(00) Average of Survey Results for Area
Figure 7. Bikini Island - Background Radiation Survey Results
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Nineteen coconut samples were collected from thirteen different locations
on the island. Green coconuts were used for almost all samples and the
meat and milk were analyzed separately. Only 137Cs and 90Sr were
detectable in any of the samples. Tritium analyses were performed on
the milk from selected coconuts but all results were below the lower
limit of detection (0.4 pCi/ml).
Table 1. Mean 137Cs and 90Sr Concentration in Food From Bikini Island
(pCi/g wet weight)
Sample
Coconut meat
Coconut milk
Pandanus
Arrowroot f
1969
137Cs Range
120 4 - 480
130 48 - 270
130 26 - 400
0.6 0.4 - 1.1
1967*
137Cs
200 ± 2.6
1969
90 Sr
0.31
28
2.4
*Data from reference number 2.
"^Prepared by grinding, rinsing three times with salt water and once with
fresh water. (Marshallese method of preparation)
ENEU ISLAND
The second largest island in the atoll, and the site of the base camp for
the cleanup operation, Eneu, was found to be considerably lower than
Bikini in external background (Figure 3). Although an exposure rate
of 50 yR/hr was obtained at one depressed location during the early
stages, filling of this "borrow pit" area reduced the level to
approximately 10 yR/hr. The exposure rate generally ranged from less
than 10 to 20 yR/hr. Of particular interest was an aircraft decontamination
pad adjacent to the parking apron of the airstrip which bisects the island.
Surveys of this area showed background levels to be less than 20 yR/hr for
all exterior surfaces. The interior of the drain measured approximately
50 yR/hr.
Thirteen cable spools, giving a combined contact reading of 200 yR/hr,
represented the only radioactive scrap located on the island. These
were removed and disposed of at sea.
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GU-000 Range ol Survey Results in micro-R/hr
'J tuivoy R.-sult in muio-R/hr al thai Location
LAGOON
ENEl) ISLAND
500 1000
SCALE
Figur* 3. En«u liland - Background Radiation Survay R«ull>
2000
FEFT
10
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The areas southeast and northwest of the runway were stripped for
planting in the same manner as Bikini.
Coconut, arrowroot, and pandanus samples were collected and analyzed
(Table 2). In addition, coconut crabs and marine life were sampled
by the Laboratory of Radiation Ecology of the University of Washington.
Table 2. Mean 137Cs and 90Sr Concentration in Food from Eneu Island
(pCi/g wet weight)
Sample
Coconut meat
Coconut milk
Pandanus
Arrowroot
137Cs
21
23
87
0.7
90Sr
.08
0.4
137Cs-1967*
28 ± 0.42
14 ± 0.24
*Data from-reference number 2.
"^Prepared by grinding, rinsing three times with salt water and once with
fresh water. (Marshallese method of preparation)
OBOE (AEROKOJ) - TARE (ENEMAN) COMPLEX
Located on the southern side of the atoll, this complex consists of five
islands, Aerokoj, Aerokojlol, Bikdrin, Lele, and Eneman with man-made
causeways connecting Bikdrin to the islands on each side of it.
OBOE (AEROKOJ) - PETER (AEROKOJLOL) - ROGER (BIKDRIN)
As indicated by Figure 4 the first two islands are contiguous and are
connected to Bikdrin (Figure 5) by a causeway. The measured background
gamna radiation levels were 10 yR/hr or less over all of these islands.
No radioactive scrap reading in excess of 30 yR/hr was found on the land or
reef areas near these islands. Gamma spectroscopy showed 60Co to be the
contaminating radionuclide in the few pieces of scrap metal found.
The only coconut trees on the complex were found on the east end of
Aerokoj. No pandanus or arrowroot was found.
11
-------
ro
PETER (AEROKOJLOL)
OBOE (AEROKOJ)
00 Survey Rotuk in micro—R/hr at that Location
Flgur* 4. Obo«—P«tar Island — Background Radiation Survey RttulH
SCAU M HUNOMDS Of TAROS
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TARE (ENEMAN)
SHALLOW PONDS
ROGER (BIKDRIN)
00-000 long, ol Sutvoy Ronilti in mkro-l/hr
00 Sutvcy (xuk in miao-t/hr ol rtieH Location
Rtunt S. Iaf*-Sil«ar-Tara IllonA - (ockanMind lodiotion Sucvoy R«vh
SCALE IN YAMS
750
1500
-------
Table 3. Mean 137Cs and 90Sr Concentration in Aerokoj Coconuts
(pCi/g wet weight)
Sample . 137Cs 90Sr
Meat 2.6 0.009
Milk 3.0
SUGAR (LELE) AND TARE (ENEMAN)
For all practical purposes these are one island, although marked
differences in background levels are seen between the east and west
ends (Figure 5).
Several nuclear detonations occurred on the west end of Eneman which
as a result is only about half its original size.
Soil samples were taken at four locations on Eneman where measured
backgrounds were 60, 100, 250, and 500 yR/hr respectively. Each
sample represented approximately one square foot to a depth of one to
two inches. Three main contributors to the gamma exposure rate were
identified: 60Co, 137Cs, and 102mRh. Although the 102IT1Rh component of
the gamma spectrum probably contained some 106Ru-Rh, the concentrations
were calculated assuming only 102mRh to be present. A wide variation
in the relative amount of 137Cs was seen, but in general the amounts
varied inversely with the background exposure rates. Figure 6 shows
the projected decay of the sample taken in the 500 yR/hr background area.
The relative amounts of each nuclide are indicated at T (July 1969).
o
Figure 7 gives the projected exposure rate as a function of time. Two
of the samples were also analyzed by radiochemical methods for alpha
emitting nuclides (Table 4).
14
-------
137
Cs
197O
1980
1990
2OOO 2O1O
YEAR
2020
2O3O
Figure 6. Tare Soil — Composite Decay Projection
15
-------
1.O
0.1 —
.01
1970
198O
1990
20OO 2O1O
YEAR
2020
2O3O
Figure 7. Tare — Projected Exposure Rate Reduction
16
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Table 4. Alpha Emitting Nuclides in Soil - Eneman (pCi/g air-dried weight)
Nuclide
239, 240pu
238Pu
241Ar,
100 yR/hr area
27
11
2
500 yR/hr area
410
220
40
UNCLE (ENIDRIK)
The island of Enidrik is located west of Eneman on the southern rim of
the atoll (Figure 8). The northwest end of the island is heavily
vegetated and showed background radiation levels of 100 to 300 yR/hr
over most of the area.
The central portion of the island consists of coral rubble overgrown
by ipomoea vines and the background radiation levels are generally
10 yR/hr or less. Progressing toward the narrow eastern end of the
island the vegetative cover remains thin. Two large sandy areas,
devoid of vegetation, dominate this end. Background levels remain
at 10 yR/hr or less over the great majority of the eastern end.
No coconut trees were found on the island. A few scattered mature
pandanus were seen, and one small grove of immature pandanus was
located on the western end. One arrowroot sample was taken at this
last location where the background was 250 yR/hr. The 137Cs concentra-
tion in the arrowroot was 0.2 pCi/g (wet weight) after processing as
previously described.
A soil sample taken in a 300 yR/hr area showed 102mRh, 137Cs, and 60Co
to be the major gamma emitting contaminants (78%, 14%, and 8% respectively
by concentration).
Only a few pieces of radioactive debris were found and these were
removed for burial at sea.
17
-------
00
UNCLE (ENIDRIK)
SCALE IN THOUSANDS OF YARDS
1
00—000 Range of Survey Results in micro—R/hr
00 Survey Results in micro—R/hr at that Location
Figure 8. Uncle Island — Background Radiation Survey Results
-------
1.0
0.1
0
a
x
UJ
-------
VICTOR (LUKOJ) AND WILLIAM (JELETE)
These two adjacent islands located at the southwest end of the atoll
are very similar in vegetative cover and background radiation levels.
In general, the background ranges from 10 to 180 yR/hr on Lukoj and
10 to 150 yR/hr on Jelete (see Figures 10 and 11). No radioactive debris
was found on either island.
A soil sample taken on Jelete showed the primary contaminants to be
137Cs (75%), 60Co (12.5%) and 102mRh (12.5%). Figure 12 indicates the
projected exposure rate reduction based upon these percentages. This
sample also contained 82 pCi/g of 239,2
-------
VICTOR (LUKOJ)
00—000 Range of Survey Results in micro—R/hr
SCALf IN YARDS
250
500
Hour* 10. Victor Island - Background Radiation Survey Rcsvks
21
-------
ro
ro
Floating Dock on Beach
WILLIAM (JELETE)
00—000 Range of Survey Results in micro—R/hr
00 Survey Result in micro—R/hr at that Location
SCALE IN YARDS
150
300
Figure 11. William Island — Background Radiation Survey Results
-------
1.O
3
V)
0
a
x
LLl
197O
1980
199O 2OOO 2O1O 2O2O
YEAR
Figure 12. William - Projected Exposure Rate Reduction
23
2O3O
-------
BRAVO IBOKDROLUL)
ALPHA IBOKAETOKTOK)
SCAIE IN HUNDREDS OF YARDS \ 00-000 Range ol Suivoy Results in micio-R/hi
01 S 10
Figure 13. Alpha-Bravo—Zebra Islandi - Background Radiation Survey Roiullt
ZEBRA (OROKEN)
-------
A single soil sample from Bokdrolul showed approximately 85% 137Cs
and 15% 60Co.
No edible plants were found on any of these islands.
Since the maximum exposure rate found for this group was 50 yR/hr,
the exposure rate reductions were not projected.
CHARLIE (NAM)
As indicated by Figure 14, the external radiation levels on Nam, located
in the northwest corner of the atoll, are slightly higher than those on
Bikini with one "hot spot" of 500 yR/hr found near the northwest side
of the island. A single soil sample taken in a background area of
approximately 200 yR/hr showed the concentration of gamma emitting
nuclides to be composed of about 50% 137Cs, 33% 60Co, and 17% 125sb.
The exposure rate reduction as a function of time for this composition
is given in Figure 15.
Radioactive scrap was found at several locations on the island. The
maximum reading obtained on any piece of scrap was 500 yR/hr. All
radioactive scrap reading in excess of 100 yR/hr (gairnia) was buried
at sea. Less radioactive material was buried on land with the non-
radioactive debris.
Although this is the third largest island and one which had been pre-
viously utilized as a source of food materials by the Bikinians,
there are at present no edible land plants or coconut crabs on the
island.
A sample of fresh water from Nam, taken in 1964 and supplied to WERL
by the Laboratory for Radiation Ecology, contained 15 pCi of 3H/ml.
Tritium levels in all other water samples from various islands were
less than 0.4 pCi/ml.
A sample from a Portulaca plant (high water content) taken in June 1969
contained 1.5 pCi of 3H/ml of extracted water. The concentration of
137Cs in the plant material was 210 pCi/g and of 60Co was 3.8 pCi/g
wet weight.
25
-------
ro
00—000 Range of Survey Results in micro—R/hr
00 Survey Results in micro—R/hr at that Location
SCALE IN THOUSANDS OF YARDS
1
CHARLIE (NAM*
Figure 14. Charlie Island - Background Radiation Survey Results
-------
1.0
.01
1970
1980
199O
2OOO 2O1O
YEAR
2O2O
2O3O
Figure 15. Charlie — Projected Exposure Rate Reduction
27
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DOG (IROIJ), EASY (ODRIK), FOX (LOMILIK), AND GEORGE (AOMEN)
The northern complex of islands is shown in Figures 16 and 17. Iroij
and Odrik are connected by a long man-made causeway, while Odrik is
in turn connected to Lomilik by a shorter causeway. Lomilik and
Aomen are differentiated only by a narrowing of the land mass.
Only Lomilik contained any significant amount of radioactive debris and
displayed relatively high levels of external background. The maximum expo-
sure rate due to soil contamination measured on each of these islands was:
Iroij - 40 yR/hr
Odrik - 10 yR/hr
Lomilik - 500 yR/hr
Aomen - 100 yR/hr
The debris from Iroij, Odrik, and Aomen was buried on land. A large
amount of non-radioactive scrap was removed from the ocean reef on
Aomen and also buried on land.
All radioactive metallic debris on Lomilik (maximum 500 yR/hr) was
removed and buried at sea. Fragments of concrete from scientific
installations, all of which measured less than 100 yR/hr, were
buried on land.
One low lying, algae encrusted area on Lomilik showed background radiation
levels of 500 yR/hr. A soil sample taken at this location contained
approximately 55% 102mRh.and 45% 6°Co as measured by gamma ray spectroscopy.
The projected exposure rate reduction for this location is given by
Figure 18. Since the absence of 137Cs would indicate that this sample
is atypical, a plot is also shown assuming that 20% of the total
activity is due to 137Cs and that the i°2tnRh and eoco retain their
same relative concentrations. This might be more applicable to other
locations on Lomilik.
Two concrete bunkers on Aomen had areas on the tops and sides which
read 5-7,000 yR/hr (e + y) at contact. The gamma exposure rate was less
than 200 yR/hr. Since the potential for exposure to individuals from
these sources was negligible, it was decided to leave the bunkers as
typhoon shelters.
28
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DOG IIROD)
ro
EASY IODRIK)
00—000 Range of Survey Results in micro—R/hr
00 Survey Result in micro—R/hr at that Location
Figure 16. Dog—Easy Islands — Background Radiation Survey Results
SCALE IN YARDS
750
1500
-------
CO
o
FOX (LOMILIK)
GEORGE (AOMEN)
OO 000 Range of Survey Remits in micro—R/hr
OO Survey Reiub in mi
-------
\
Assumed 20 % Cs
197O
198O
199O
2OOO 201O
YEAR
2O2O
2030
Figure 18. Fox — Projected Exposure Rate Reduction
31
-------
No edible land plants were found on the complex.
REEF STRUCTURES
Several large structures,mostly reinforced concrete, constructed on the
coral reef are found between Nam and Iroij and one is located near the
sand bar, Bokbata, southwest of Nam. All of these structures were
surveyed with the following results:
1. Able (Bokbata) Reef Structure - one small door and several
metal pieces on reef 200-300 yR/hr. Remainder 5-40 yR/hr.
2. Charlie (Nam), Dog (Iroij) Reef Structure #1 - several
small metal plates on top of concrete foundation 100-500
yR/hr (these are awash at high tide). Remainder 5-10 yR/hr.
Structures #2 and #3 - all readings less than 10 yR/hr.
These structures were judged to constitute no radiological hazard and
Trust Territory representatives assessed the physical hazard as in-
sufficient to justify the costly and time consuming effort which would
be required to remove them.
DOSE ASSESSMENT
The traditional living pattern of the Bikinians centers around communal
life on the island of Bikini where the permanent village and social and
religious centers were located. Temporary settlements were located on
other islands, primarily Eneu. In view of the Ad Hoc Committee's
recommendation to limit initial resettlement to these two islands, it
is assumed that the doses received from brief visits to other islands
in the Atoll will be small relative to that received from residence on
Bikini. In addition the uniformly low exposure rates encountered on
Eneu represented a potential exposure which is negligible even for
continuous occupancy. For this reason, the treatment of dose considera-
tions will be limited to the island of Bikini.
EXTERNAL DOSE ASSESSMENT
As indicated previously the island of Bikini was extensively monitored
with portable ganrna survey meters. Because the soil samples indicated
32
-------
a large abundance of 137Cs relative to other gamma emitting nuclides no
effort was made to correct the readings obtained from the scintillators
which were calibrated against 137Cs.
The islands can be divided into essentially three domains:
1. Beach Area - uniformly low background of approximately
10 yR/hr.
2. Village Area - located along lagoon side of the island. For
purposes of this report two sets of data were obtained:
a. From lagoon road to approximately 250 feet inland
the mean background was 52 yR/hr.
b. From lagoon road to beach - 35 yR/hr. Considering
these two areas together the mean background would
be 44 yR/hr.
3. Interior - used for agriculture. This was considered to
include the area within the perimeter road, excluding the
village area. The mean background was 86yR/hr.
Experience obtained during the clearing operation indicates that total
removal of the vegetative cover and turning of the soil as occurred
during the grading of the perimeter and cross island roads results
in a rapid reduction of the measured exposure rate. If it is assumed
that the village area will be essentially cleared and covered with
crushed coral as is customary, it would seem that an expected reduction
of the mean exposure rate by a factor of two would be a conservative
estimate.
Figures 19 and 20 show the integrated exposure for the village and in-
terior areas. (The beach is assumed constant at <10 yR/hr). By making
assumptions as to the residence time in each domain, the external gamma
dose may be estimated.
If the following assumptions for residence time shown in Table 5 are
taken, the integral (at any age) dose to children born on Bikini in 1970
would be the figures shown in Table 6.
33
-------
100
Mean
Mean/2!
1970
198O
199O
2000 2O10
YEAR
2O20
2O3O
Figure 19. Bikini Integral Dose Projection — Village Area
34
-------
1OO
o>
in
0
Q
O)
ID
197O
198O
1990
2000 2010
YEAR
2O2O
2O3O
Figure 20. Bikini Integral Dose Projection - Interior
35
-------
Table 5.
Age
0-3
3-10
10-70
Estimate
Beach
0
20
10
of Where Time
Percent Time
Village
100
70
60
Is Spent by Aqe.
Spent in Each Location
Interior
0
10
20
Over Water
0
0
10
Table 6. Projected Integral Dose for A Child Born in 1970 (Bikini Island)
Time Interval (years) Integral Dose (mRad)
5 750
10 1695
20 3545
30 5275
50 . 7735
70 9355
For purposes of the above calculation, the exposure rate on the beach was
assumed constant at 10 yR/hr, on the water at 5 yR/hr, and for the village
the modified (mean/2) exposure rate was used. It is felt that all of
these estimates are conservative.
THERMOLUMINESCENT DOSIMETER PROGRAM
As a check on the validity of the ganrtia exposure rates as measured by
survey meters, thermoluminescent dosimeters were placed at six locations
on Eneu and twelve locations on Bikini. Three dosimeters were placed
at each location and left for approximately thirty days. These dosi-
meters were then collected and shipped by air to WERL where they
were read. One set of three dosimeters served as controls for each
placement period. Survey meter readings at these locations ranged
from essentially zero to ninety yR/hr. Because of the relatively large
36
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contribution of the exposure in transit as compared to the exposure
during the placement period, wide fluctuations in net exposure as
measured by each of the three dosimeters at each location were noticed.
However, a regression analysis was performed comparing survey meter
readings to the mean TLD results at each location. The linear
relationship between the two was described by:
TLD = -1.5 + 0.8 (survey meter)
The correlation coefficient was 0.94 and the average error associated
with the replicate TLD measurements was 35%.
Throughout this report survey meter readings as obtained in the field
have been used. If it is assumed that the mean TLD value for each
station is a more accurate representation of the exposure rate, then
a further element of conservatism has been added to the external dose
estimates which are based on survey meter readings.
AIR SAMPLING RESULTS
During May-June 1970 a joint AEC-U. of W.-WERL follow-up survev was
conducted on Bikini and Eneu. The purpose of this survey was to deter-
mine the amounts of 239Pu in the soil and air. WERL was responsible
for the air sampling program.
The air sampler chosen for this effort was the Model 102 developed and
used by Reynolds Electrical and Engineering Company at the AEC's Nevada
Test Site. It was felt that the Model 102, which was designed for rugged
outdoor use under extreme weather conditions, was well-suited for the
Bikini operation. The sampler consisted of a constant-volume pump, belt-
driven by a gasoline powered engine. The only adjustments necessary were
to the carburetor for sea-level operation. All samplers were re-calibrated
for flow-rate at Bikini and the calibration was checked frequently during
the operation.
Four samplers were placed on Eneu, Figure 21, and five samplers on Bikini,
Figure 22. Bikini No. 5 and Eneu No. 1 are considered to be background
stations since they were located on the windward side of the respective
islands, overlooking the beach. Air filters were exchanged every 24 hours
for a period of 15 days on Eneu and 14 days on Bikini. Tables 7 and 8
37
-------
ENEU ISLAND
1970 COLLECTION AREAS
CAMP BLANDY
AIR SAMPLE STATIONS
SCALE 1 inch = 10OO feet
Figure 21. Eneu Island — Air Sampling Locations
38
-------
co
vo
BIKINI ISLAND
SCALE IN FEET
10OO 2000
AIR SAMPLE STATIONS
3000
Figure 22. Bikini Island — Air Sampling Locations
-------
Table 7. Composite 239Pu in Air Results for Bikini Island - 1970
Station
Date
239
Pu
(pCi/m3)
238
Pu
(pCi/m3)
1
2
3
4
5
5/29
5/29
5/29
5/29
5/29
- 6/12
- 6/12
- 6/12
- 6/12
- 6/12
5
1
1
0
1
.4
.1
.0
.6
.2
x
x
X
X
X
10
10
10
10
10
-4
-4
-4
-4
-4
<0.1
<0.1
0.1
<0.1
0.1
x
x
x
x
x
10
10
10
10
10
-4
-4
-4
-4
-4
Table 8. Composite 239Pu in Air Results for Eneu Island - 1970
Station
1
2
3
4
Date
5/28
5/28
5/28
6/2
6/12
6/12
6/12
6/12
239pu
(pCi/m3)
0.4 x 10
0.4 x 10
0.4 x 10
0.4 x 10
-4
-4
-4
-4
238pu
(PCi/m3)
0.1 x 10
0.1 x 10
0.1 x 10
<0.1 x 10
-4
-4
-4
-4
40
-------
list, respectively, the composite 239Pu in air results for Bikini and Eneu. The
composite results were obtained by analyzing one half of the filter for each day
and compositing bv station over the total sampling period. For Bikini the 239Pu
-43 -43
results ranged from 0.6 x 10 pCi/m to 5.4 x 10 pCi/m . All results for Eneu
A *D
were 0.4 x 10" pCi/m . For comparison the average value for 239Pu background in
-4 3
the U.S. during 1968 was 0.4 x 10 pCi/m . In order to assess the daily vari-
ation in air concentration, the remaining one-half of the individual filters from
station No. 1 on Bikini were analyzed separately. These results are listed in
Table 9. The results ranged from <0.7 x 10 pCi/m to 7.9 x 10 pCi/m . The
-4 3
average for all samples at this station is 4 x 10 pCi/m which compares quite
-4 3
favorably with the value of 5.4 x 10 pCi/m for the composite. Although some
variation in daily levels is evident from these data, the distribution of results
appears to be about what might be expected allowing for slight differences in
wind conditions. It should be noted that station No. 1 is located on the down-
wind side of the lagoon road and was subjected to frequent clouds of dust
stirred up by the survey party's jeep. In any event, it is doubtful that
significantly higher concentrations would be encountered under normal weather
conditions. Although it is assumed that the plutonium us present in the oxide
form (incoluble), when comparison is made to the more stringent FRC guide for
-2 3
soluble plutonium of 6 x 10 pCi/m for an individual in the population, the
above results are lower than the guide by approximately two orders of magnitude.
This is not meant to imply however, that unfavorable weather conditions suf-
ficient to create Pu concentrations high enough to be of some radiological con-
cern could not exist during other times of the year.
SUMMARY AND RECOMMENDATIONS
External radiation levels were measured on all islands of Bikini Atoll as part
of the clean-up program. The highest exposure rate was measured on Tare(Eneman)
where a low lying algae covered area showed 800 yR/hr. The maximum exposure
rate encountered on the islands scheduled for rehabilitation, Bikini and Eneu,
was 120 yR/hr in the interior of Bikini. Other islands exhibiting exposure
rates greater than those found on Bikini were:
Uncle (Enidrik) - 300 yR/hr
Victor (Lukoj) - 180 yR/hr
William (Jelete) - 150 yR/hr
Charlie (Nam) - 500 yR/hr
Fox (Lomilik) - 500 yR/hr
41
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Table 9. Daily 239Pu in Air Results for Station 1 Bikini Island - 1970
Date Collected
5/30/70
5/31/70
6/01/70
6/02/70
6/03/70
6/04/70
6/05/70
6/06/70
6/07/70
6/08/70
6/08/70
6/10/70
6/11/70
6/12/70
Hour
1010
1330
0750
0725
0755
0730
0840
0745
0730
0730
2335*
0700
0700
0955
239pu
(pCi/m3)
<0.7 x 10~4
0.7 x 10"4
1.2 x 10"4
7.2 x 10"4
5.5 x 10"4
4.0 x 10"4
7.9 x 10"4
4.7 x 10"4
2.5 x 10"4
4.8 x 10"4
6.1 x 10"4
1.2 x 10"4
2.6 x 10"4
4.0 x 10"4
*Estimated time of sampler shutdown due to heavy rainstorm. Based on
vibration hour meter.
42
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Soil samples taken on Bikini showed greater than 95% of the exposure
rate to be due to the 137Cs and thus the reduction in exposure rate can be
assumed to closely follow the decay of 137Cs. Soil samples from the
other islands showed varying amounts of 60Co and 102MRh in addition to
the 137Cs. The reduction in exposure rate due to radioactive decay on
these islands should be much more rapid than for Bikini. Comparing the
decay curves for these islands with that for Bikini, it can be seen that
within approximately ten to fifteen years only Eneman will have an external
background higher than that of Bikini. It is recommended that a re-survey
to verify this projection be conducted in about ten years in anticipation
of unrestricted use of the atoll. In the meantime, the recommendation
of the Ad Hoc Committee that occupancy of the above islands be limited
to visits of short duration should be followed.
The remaining islands of the atoll are lower in radiation levels than
Bikini and should not be restricted against continuous occupancy on
that basis. This is particularly true of the Oboe (Aerokoj), Peter
(Aerokojlul), Roger (Bikdrin) complex where the lowest levels on the
atoll were found. In addition, coconut samples from Aerokoj were lower
in 137Cs and 90Sr content than those from Bikini or Eneu. Agricultural
development of these islands should be encouraged. While the external
levels on Sugar (Lele) are as low as those on the other three islands,
the fact that it is contiguous with Tare (Eneman) would make it advisable
to restrict the use of this island at the present time. The causeway
joining Lele to Bikdrin makes a logical dividing line for indicating
this restriction.
Sampling of food items presently growing on the atoll indicated mean
concentrations of 137Cs and 90Sr which are essentially in agreement
with those obtained in 1967. It should be pointed out that the planting
of new species of foods on the islands will require additional sampling
at the time of their reaching maturity in order to assess the potential
internal dose. Internal dose estimates have been performed by Gustafson
utilizing the 1967 data and would appear to be valid for the 1969
data as well. Results of the 1970 survey for plutonium in air are
approximately two orders of magnitude below the FRC guide for an individual
43
-------
in the population and would not significantly affect these estimates. As
a result those computations have not been repeated here.
The concentrations of 90Sr would seem to be of greatest concern with
respect to internal dose. In this regard the recommendations of the Ac[
Hoc Committee for removal of top soil from the site of newly planted
pandanus and possibly breadfruit trees, and the addition of a calcium
supplement to the diet should be most effective in reducing the dose
due to 9°Sr.
44
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REFERENCES
1. Beck, H. L., B. G. Burton, T. F. McCraw. External Radiation
Levels on Bikini Atoll. HASL-190. (May 1967}T
2. Held, E. E. Letter with attachments to J. N. Wolfe. University
of Washington. (January 8, 1968)
3. Report of the Ad Hoc Committee to Evaluate the Radiological
Hazards of Resettlement" of the Bikini Atoll.Attached to AEC
News Release No. L-191.(August 12, 1968)
4. Crocker, G. R., M. A. Connors, D. T. K. Wong. Some factors for
the calculation of infinite plane exposure rates from gamma radiation.
Health Physics. (September 1966)
5. Gustafson, P. F. Radi glogical Report on Biki ni Atol1, Apri1 1968
and Additions to Radiological Report on Bikini Atoll, May 1968.
DBM-ATE(1968)
6. Johns, Frederick B. Southwestern Radiological HealtlvLaboratory
Handbook of Radiochemical Analytical Methods—SWRHL-11. (March 1970) •
45
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DISTRIBUTION
1-15 WERL, Las Vegas, Nevada
16 Robert E. Miller, Manager, NVOO/AEC, Las Vegas, Nevada
17 Robert H. Thalgott, NVOO/AEC, Las Vegas, Nevada
18 Henry G. Vermillion, NVOO/AEC, Las Vegas, Nevada
19 Chief, NOB/DNA, NVOO/AEC, Las Vegas, Nevada
20 Robert R. Loux, NVOO/AEC, Las Vegas, Nevada
21 Donald W. Hendricks, NVOO/AEC, Las Vegas, Nevada
22 Technical Library, NVOO/AEC, Las Vegas, Nevada
23 Mail & Records, NVOO/AEC, Las Vegas, Nevada
24 Martin B. Biles, DOS, USAEC, Washington, D. C.
25 Director, DMA, USAEC, Washington, D. C.
26 John S. Kelley, DPNE, USAEC, Washington, D. C.
27 Philip Allen, ARL/NOAA, NVOO/AEC, Las Vegas, Nevada
28 Gilbert J. Ferber, ARL/NOAA, Silver Spring, Maryland
29 Stanley M. Greenfield, Assistant Administrator for Research &
Monitoring, EPA, Washington, D. C.
30 Acting Deputy Assistant Administrator for Radiation Programs, EPA,
'Rockville, Maryland
31 Paul C. Tompkins, Acting Director, Division of Criteria & Standards,
Office of Radiation Programs, EPA, Rockville, Maryland
32 Ernest D. Harward, Acting Director, Division of Technology Assessment,
Office of Radiation Programs, EPA, Rockville, Maryland
33 Bernd Kahn, Chief, Radiological Engineering Laboratory, EPA,
Cincinnati, Ohio
34 - 35 Charles L. Weaver, Acting Director, Division of Surveillance &
Inspection, Office of Radiation Programs, EPA, Rockville, Maryland
36 Gordon Everett, Director, Office of Technical Analysis, EPA,
Washington, D. C.
37 Regional Administrator, EPA, Region IX, San Francisco, California
38 Eastern Environmental Radiation Laboratory, EPA, Montgomery, Alabama
39 Acting Director, Twinbrook Research Laboratory, EPA, Rockville,
Maryland
40 William C. King, LLL, Mercury, Nevada
41 James E. Carothers, LLL, Livermore, California
42 Roger E. Batzel, LLL, Livermore, California
43 William E. Ogle, LASL, Los Alamos, New Mexico
44 Harry S. Jordan, LASL, Los Alamos, New Mexico
-------
Distribution (cont'd)
45 Arden E. Bicker, REECo, Mercury, Nevada
46 Clinton S. Maupin, REECo, Mercury, Nevada
47 Charles F. Bild, Sandia Laboratories, Albuquerque, New Mexico
48 Robert H. Wilson, University of Rochester, Rochester, New York
49 Richard S. Davidson, Battelle Memorial Institute, Columbus, Ohio
50 Frank E. Abbott, USAEC, Golden, Colorado
51 John M. Ward, President, Desert Research Institute, University of
Nevada, Reno
52 - 53 DTIE, Oak Ridge, Tennessee (for public availability)
54 Frank Cluff, NVOO/AEC, Las Vegas, Nevada
55 Thomas F. McCraw, DOS, USAEC, Washington, D. C.
56 William Hills, USAEC, Honolulu, Hawaii
57 Edward E. Held, Lab. of Radiation Ecology, Univ. of Washington, Seattle, WA
58 Robert A. Conard, Brookhaven National Lab., Upton, N<. Y.
59 - 63 Edward Johnston, Trust Territory-Pacific Islands, Saipan, Mariana Is.
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