Report of the Radiological Clean-Up of Bikini Atoll

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Al Ian E. Smith and William E. Moore Office of Dose Assessment & Systems Analysis Western Environmental Research Laboratory This study performed under a Memorandum of U.S. ATOMIC ENERGY COMMISSION

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This repor~ was ~repared as an account of work sponsored by zhe United States Government. Neither the United States nor =he Urited States Atomic Energy Commission, nor any 01z Iheir employees, nor any of their contractors, subcontr?c~ors, or their employees, makes anv warranty, express or ‘mpliea, or assumes any legal liability or responsibility for zhe accuracv, completeness or usefulness of anv informat~on, apparatus, product or process disclosed, or represents that its use would not infringe privately-owned rights. Available from the National Technical Information Service, Price: paper copy $3.00; microfiche $.95.

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OF BIKINI ATOLL Office of Dose Assessment & Systems Analysis ENVIRONMENTAL PROTECTION AGENCY This study performed under a Memorandum of U.S. ATOMIC ENERGY COMMISSION

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4S a result of a decis’on hy President ~ohnson 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 rehabilitating the islands of Bikini and Eneu in preparation for the resettlement of the Bikinian people to their home islands. Radiological Safety Advisors were provided by tbe \iestern E~vironmental 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 redevelopment. Upon completion of these objectives, the islands were turned over to the Trust Territories for the agricultural phase of the ~roaram. This report describes the radiological conditions detected before, durinq and following the clean-u~ effort. The highest exposure-rat~ measured was 44 uR/hr. Inteqral dose calcu s’pent in various areas of the island and on the shielding values from coral aggregate in the vi projected external whole body dose for a person living there for 70 years would be less than 10 on the islands of Bikini and Eneu was for :he proposed villatle area on Bikini ations involving theoretical time periods lagoon and considering lage area were made. The born on Bikini in 1970 and

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OBJECTIVE OF CLEANUP PHASE EXTERNAL DOSE ASSESSMENT THERMOLUMINESCENT DOSIMETER PROGRAM AIR SWPLING RESULTS SUMMARY AND RECOMMENDATIONS

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Bikini Island - Background Radiation Survey Results Eneu Isl?nd - Background Radiation Survey Results Oboe - Peter Island - Background Radiation Survey Results Tare Soil - Composite Decay Projection Tare - Projected Exposure Rate Reduction Uncle Island - Background Radiation Survey Results Uncle - Projected Exposure Rate Reduction \!ictor Island - Background Radiation Survey Results bjilliam Island - Background Radiation Survey Results Milliam - Projected Exposure Rate Reduction Charlie Island - Background Radiation Survey Results Charlie - Projected Exposure Rate Reduction Dog - Easy Islands - Background Radiation Survey Results Fox - George Islands - Background Radiation Survey Results Fox - Projected Exposure Rate Reduction Bikini Integral Dose Projection - Village Area Bikini Integral Dose Projection - Interior Eneu Air Sampling Locations Bikini Air Sampling Locations

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LIST OF TABLES 1. Mean ‘37C5 and ‘OSr Concentration in Food from Bikini Island (pCi/g et weight) 2. Mean 137CS and ‘OSr Concentration in Food from Eneu Island (pCi/g wet weight) 3. Mean ‘37CS and ‘“Sr Concentration in Aerokoj Coconuts 4. Alpha Emitting Iiuclides in Soil - Eneman (pCi/g air-dried 5. Estimate of \dhere Time Is Spent by Age 6. Projected Integral Close for A Child Born in 1970 (Bikini 7. Composite 239Pu in Air Results for Bikini Island - 1970 8. Composite 239Pu In Air Results for Eneu Island - 1970 9. Dailv 239Pu in Air Results for station I Bikini Island - 1970

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Dur-,:-,gthe period ,946 through 1958, the atoll of Bikini, detsndtlons. ?fter the atoll of Bikini was selected as a the Iative population, numbering approximately 166, was eventually re~~~~~ed in 1948 on Kili, a single island in the southern Nlarshal]s, following brief stays on Rongerik and }~~~ajaleinatolls. Discrete test series were conducted at Bikini Atoll in 19~6, 1954, 1956, and 1958 and included both fission and fusion devices. Due to their proximity to the detonation sites, or the vagaries of the wea~her, 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 conducted under the auspices of the Division of Bioloqy and [?edicine of the U. S. Atomic Energy Commission. The 1967 survey ,yielded an extensive amount of data relative to the external radiation levels (1) and the concentration of radioactive materials in the marine environment as well as in the edible land !]lants ~nd animal life. (2) Followinq the 1967 survey, an Ad Hoc Committee was convened to evaluate—— the radiological hazards of resettlement of the Bikini P,toll. The conclusions of the cornnittee included the followinq statement: “The ex~osures to radiation that would result from the repatriation of the Bikini people do not offer a significant threat to their health and safety. ,,(3) On August 12, 1968, President Johnson announced the decision to return the Bikinians to their atoll. A joint ,4EC-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.

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OBJECTIVE OF CLEAN-UP PHASE The conclusions of the Ad Roc Committee stated that zhe islands of—— Bikini and Eneu could be used for continuous occupancy and agricultural 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 com~arison with previously collected data. Althouqh Dermanent occupancy was to be limited to the islands of Bikini and Eneu, the Ad Hoc Conmictee further concluded that “radioactive scrao—— should be removed from the islands adjacent to former shot sites.” Since these islands may be used for the collection theit- qgs for human consumption, removal of make the scrap unavailable for collection by The final object scrap from each cited for Bikini of birds, turtles, and radioactive debris would , therefore, included theves of the clean-up program, 1 physical hazards and the disposal of all radioactive sland of the atoll .in addition to the specific measures The Mestern Environmental Research Laboratory (NERL), 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 urogram was to be conducted of all edible varieties of food found to be growing there. Analyses of samples were to be Perfomled byldEf?L at one or both of its two laboratories, located in Honolulu, Hawaii and Las Vegas, Nevada.

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Rather thzn establish firm, restrictive criteria for the removal of radioactive arc~ facts, or the elimination of high background* areas from the Islands of the atojl , each situation was viewed in terms of the potential exposure ~ersus benefit. All debris or artifacts having little or no useful val~e w~s removed, All scrap metal or concrete with contact readings greater than 100 micro-Roentgen per hour (pR/hr) was treated as radloacti%:e waste and buried at sea. Three specific locations were selected for this burial (Figure 1). In some cases, scrap reading less than 100 uR/hr was buried on land together with non-radioactive debris. This was oniy done on islands where areas exhibiting background levels in excess of 100 uR/hr were found. No radioactive debris at any level of activity was buried on the islands of Bikini, Eneu, or The exterior of several bunkers, located on the no~thern complex (Iroij, Odrik, Lomilik, and Aomen) and Nam, exhibited.levels of radioactivity up to 7,000 pRad/hr (B + y) at contact. The net gamma levels were 200 ~R/hr maximum. The levels inside the bunkers were less than 10 uR/hr, however. Since the potential for personnel exposure was negligible, ~nd the bunkers were desired as typhoon shelters and storage buildings by the natives, the larger bunkers were left Several instances of high background levels, greater than 200 ljR/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 operations as well as from natural sources. Natural background levels in this part of the world result primarilv from Cosmic rays and are qenerally less

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Tabulations for the islands cf ~i kini ,Ato;” on the following paqes wiil 1. the backgl”ound gamma exposure r?z?s as i-easured with a Baird Atomic NE-148A scintillatcr calibrated against 1S7CS, 2, a summary of the radiological waste removal and dis~osal , 3. results of samole ?nalyses and, 4. when appropriate, projection of zhe background decay as a function of time. In order to estimate the expected reduction in exposure rate for the various islands as a function of time, it ,:as necessary to develop weighting factors for each of the gamna 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 oversim~iification bu~ would tend to give conservative results. The data of Crocker, Connors, ar?c hlong were used to indicate the relative effect of each nuclide on the exposure rate. Since 10~mRh was not among the nucl ides included in their tabulation, data from their table were normalized by effective enerqv snd number of photons per disintegration and plotted. The exposure rate factor for 1°2mRh effective energy 0.62 MeV was taken from this curve and corrected for 2.96 gamma per disintegration.* The final tabulation of the cmposite exposure rate reduction was then calculated using the decay factor, initial concentration and exposure rate weighting factor. *Decay scheme taken from Table of the Isotooes - Ledever, Hollander, and

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Gamma ra. spectrum analysis and strontium ana.lysls on all coconut, panda nl~s, in Honolulu, Hawaii. Edible portions of the samples were ground and couhted The speczral range covered was zero to two MeV. At the concentrations Of ‘37CS 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 ,;as 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 associated with this procedure is approximately ten percent at the levels of ‘OSr All tritium and plutonium analyses were performed at ~I!EPL,Las Vegas, Nevada. urnwas determined by liquid scintillation counting of the water recovered coconut milk and from selected soil samples. The minimum sensitivity for procedure is 0.4 pCi/ml for five ml of recovered water. At this concenon z$e error term for the 2 sigma confidence level is I 100 percent. Analyses of the coconut milk and soil samples indicated the concentrations of tritirim were less than the minimum detectable level. Plutonium analyses which were performed on soil samples were by radiochernical 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 t 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 radionucl ides and to estimate their relative contribution to the total activity.

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The island of 2ik.ini is the largest in the atoll, having an area of about 0.6 square wiles and has traditionall,v been the “home island” of the ~ikinia)~s. Individual land rights extend from the lagoon TO the ocean. It is anticipated that the villaae ,)ill be rebuilt along the lagoon shore ‘;jit-tlconmunity buildings heinc located about midvlav along the length. The island was ~repared for agricultural red~veloprnent by cutting parallel strips through the vegetation along the length of the island. The striDs, cut on 56-foot centers, were approximately 20 feet wide. The vegetative cover was knocked down and left in place to p)-ovide additional organiG matter for thp soil. ThP strips were surveyed and background gamma radiation levels recorded at 250-foot intervals along their lenQth. Figure 2 illustrates the background variation by depicting the ranqe and average of radiation measurements for areas consisting of approximately four strips. Although a large amount of debris was found on [?ikini (from testing program and Norld !lar II) with one exception, none was radioactive. One pile of roofing oziper 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 \~R/hr, was loaded into 55-gallon drums and disposed of in the ocean south The measured exposure rate; were 10 l~R/hr or less alonq the beaches, and ranged from 20-120 llR/hr inland. Soil samples taken at three locations having measured backgrounds of 20, 70, and 100 ,,R/hr showed 137CS and eoCo to be the major gamma mitting 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 v!as present in amounts ranging from 10-50% of the lSTCS 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.

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,11~?teen coconut samples were collected from thirteen different Iccations on The island. Green coconuts were used for almost all samples ar,tithe de:?ctable in any of the samples, Tritium analyses were pertorwez cn th: milk from selected coconuts but all results were below the lGI;:sr Ta51e 1. Mean *37CS and 90Sr Concentration in Food From Bikini Isjand *Data from reference number 2. ‘Prepared by grinding, rinsing three times with salt water and once with fresh water. (Marshallese method of preparation) The second larqest island in the …