Report of the Radiological Clean-Up of Bikini Atoll

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REPORT OF THE RADIOLOGICAL CLEAN-UP OF BIKINI ATOLL Office of Dose Assessment & Systems Analysis Western Environmental Research Laborat0r.y ENVIRONMENTAL PROTECTION AGENCY This study performed under a Memorandum of U.S. ATOMIC ENERGY COMMISSION

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T h i s 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, subcontractors,or their employees, makes anv warranty, express or implied, o r assumes any legal liability or responsibilitv for the accuracy, completeness o r usefulness of any information, apparatus, product o r process disclosed, or represents that its use would not infrinqe privately-owned rights. Available from the National Technical Information Service, Price: paper copy $3.00; microfiche Q.95.

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REPORT OF THE RADIOLOGICAL CLEAN-UP OF BIKINI ATOLL Allan E. Smith and William E. Moore Office of Dose Assessment p1 Systems Analysis Western Environmental Research Laboratory ENVIRONMENTAL PROTECTION AGENCY This study performed under a Memorandum o f U.S. ATOMIC ENERGY COMMISSION

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As a result o f a decision by President Johnson i n 1968, the Atoll of Bikini was the subject of an intensive clean-up e f f o r t in 1969 by a j o i n t AEC-DASA task force. The task force was responsible for rehabilit a ting the islands of Bikini and Eneu i n preparation for the resettlement of the Bikinian people t o their home islands. Radiological Safet.y Advisors were provided by the Western Environmental Research Laboratory, Environmental Protection Agency. Objectives of the clean-up effort were: removal of a l l debris from the islands; determination of existing radiation levels on each island; analysis of available food items for radionuclide distribution; and clearing o f vegetation from land for agricultural reover t o the Trust Territories for the agricultural phase of the nrogram. This report describes the radiological conditions detected before, during and following the clean-up effort. Upon completion of these objectives, the islands were turned The highest exposure-rate measured on the islands of Bikini and Eneu was was 44 p R / h r . Integral dose calculations involving theoretical time periods s’pent in various areas of the island and on the lagoon and considering shielding values from coral aggregate in the village area were made. 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. The mean exposure-rate f.or the proposed village area on Bikini

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Paq eT ABLE OF CONTENTS LIST OF FIGURES iii LIST OF TABLES iY OBJECTIVE OF CLEANUP PHASE 2 EXTERNAL DOSE ASSESSMENT 32 THERMOLUMINESCENT DOSIMETER PROGRAM 36

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LIST OF FIGURES 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 6. Tare Soil - Composite Decay Projection 15 7. Tare - Projected Exposure Rate Reduction 16 8. Uncle Island - Background Radiation Survey Results 18 I 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. 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

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LIST OF TABLES Mean 137Cs and 90Sr Concentration in Food from Bikini Mean 137Cs and 90Sr Concentration in Food from Eneu Mean 137Cs and 90Sr Concentration in Aerokoj Coconuts Estimate of Where Time I s Spent by Age Projected Integral Dose for A Child Born i n 1970 (Bikini 7. Composite 239Pu in Air Results for Bikini Island - 1970 8. Composite 239Pu i n Air Results for Eneu Island - 1970

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During the period 1946 through 1958, the atoll of Bikini, centered 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 i n 1946, 1954, 1956, and 1958 and included both fission and fusion devices. t o their proximity t o the detonation sites, or the vagaries of the weather, all of the islands of the atoll were contaminated t o sane extent by radioactive fallout. In 1964 and again i n 1967, radiological surveys of the atoll were conducted under the auspices of the Division of Biology and Medicine of t h e U. S. Atomic Energy Commission. extensive amount of data relative to the external radiation levels and the concentration of radioactive materials in the marine environment a s well asin the edible land plants and animal life. The 1967 survey yielded an 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 comnittee included t h e following statement: "The exposures to radiation that would result from the ren atria tion of the Bikini people do not offer a significant threat to their health and decision to return the Bikinians to their atoll. effort was initiated to eliminate any physical or radiological hazards remaining on the atoll and t o prepare the islands of Bikini and Eneu for agricultural redevelopment. This phase o f the clean-up program was initiated in February 1969. report result,for the most part, from the radiological clean-up effort associated with this aspect of the program. during a follow-up survey i n May-June 1970 are also reported. On August 12, 1968, President Johnson announced the The data provided i n this Air sampling data collected

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OBJECTIVE OF CLEAN W PHASE The conclusions of the --Ad Hoc Comnittee stated t h a t the islands of Bikini and Eneu could be used for continuous occupancy and agricultural development sufficient t o support the returning population. of these islands called for: 1. the removal of all test related debris with disposal a t sea of a l l radioactive debris stripping of the vegetation t o permit planting of coconuts, pandanus, breadfruit, etc. swaths which were approximately 20 f e e t wide on 56-foot centers through the vegetative cover 3 , determining residual external radiation levels a t each step of the clearing and stripping operations, and 4. obtaining samples of available food items for laboratory analysis for comarison with previously collected data. This was accomplished by cutting Although permanent occupancy was t o be limited t o the islands of Bikini and Eneu, the Ad Hoc Comnittee further concluded that "radioactive scrap should be removed from the islands adjacent t o former shot sites. " these islands may be used for the collection of birds, turtles, and t h e i r eggs for human consumption, removal of radioactive debris would make t h e 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 t o the specific measures cited f o r Bikini and Eneu. radiological surveillance operations in the Pacific for the AEC, was requested t o provide Radiological Safety Advisors t o the AEC Project Manager for the clean-up effort. I n addition, a comprehensive sampling program was t o be conducted of all edible varieties of food found t o be growing there. Analyses of samples were t o be performed by WERL a t one o r both ofits two laboratories, located in Honolulu, Hawaii and Las Vegas, Nevada.

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Rather than establish firm, restrictive criteria for the removal of radioactive artifacts, or the elimination of high background* areas from the islands of the a t o l l , each situation was viewed in terms of the potential exposure versus benefit. useful value was removed. All scrap metal or concrete with contact radioactive waste and buried a t sea. Three specific locations were selected for t h i s burial (Figure 1 ) . I n some cases, scrap reading less than 100 v R / h r was buried on land together with non-radioactive debris. This was only done on islands where areas exhibiting background levels i n excess of 100 p R / h r were found. level of activity was buried on the islands of B i k i n i , Eneu, or All debris or artifacts having little or no No radioactive debris a t any The exterior of several bunkers, located on the northern complex ( I r o i j , Odri k , Lomi 1 i k , and Aomen) and Nam, exhibited ,1 eve1 s of radioactivity 200 p R / h r maximum. The levels inside the bunkers were less than 10 p R / 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 l e f t The net gamma levels were Several instances of high background levels, greater than 200 vR/hr, due t o soil contamination were also encountered. I t was the consensus t h a t attempting t o reduce these levels by removing the top layer of s o i l would destroy the limited agricultural capability of the area, therefore, most such areas were l e f t essentially undisturbed. *The term "background" as used i n this text denotes the radiation levels a t the time of survey a n d includes that portion resulting from testing operations as well as from natural sources. Natural background levels in this part of the world result primarily from Cosmic rays and are qenerallv l e s s

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SURVEY INFORMAT ION Tabulations for the islands of B i k i n i Atoll on the following pages will 1. the background gamma exposure rates as measured w i t h a Baird Atomic NE-148A scintilla tor calibrated against 137 ~ s ~ a summary of the radiological waste removal and disposal, when appropriate, projection of the background decay a s a function of time. 3 , results of sample analyses and, In order t o estimate the expected reduction in exposure rate for the various islands as a function of time, i t was necessary t o develop weighting factors for each of the gama emitting radionuclides identified i n the analysis of soil samples. For purposes of this report, i t was assumed that the various radionuclides were uniformly distributed by depth throughout the soil and t h a t the only change in relative concentrations i s due t o the differential decay rates. This is obviously an oversimplification b u t would tend t o give conservative results. The data of Crocker, Connors, and were used t o indicate the relative effect of each nuclide on the exposure rate. was not among the nuclides included in their tabulation, data from their table were normalized by effective enerqy and number of photons per disintegration and plotted. effective energy 0.62 MeV was taken from this curve and corrected f o r 2.96 gamma per disintegration.* The final tabulation of the composite exposure r a t e reduction was then calculated using the decay factor, initial concentration and exposure rate weighting factor. The exposure rate factor for *Decay scheme taken from Table of the Isotopes - Ledever, Hollander, and

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Gama ray spectrum analysis and strontium analysis on a l l coconut, pandanus, and arrowroot samples were performed a t the WERL Pacific Operations Laboratory i n Honolulu, Hawaii. Edible portions of the samples were ground and counted without drying on a 4- by 4-inch NaI(T1) crystal multi-channel analyzer system. The spectral range covered was zero t o two MeV. A t the concentrations of 137Cs encountered i n these samples, the counting error i s approximately ten percent. (All errors referenced i n this section are 2 sigma confidence level.) Following gamma spectrum analysis the samples were ashed and the inorganic residue was analyzed f o r 90Sr. Due t o the small amount of ash produced, i t was often necessary t o composite samples from adjacent locations. Counting was performed on a low background beta counter. ated with this procedure i s approximately ten percent a t the levels of 90Sr The analytical error associAll tritium and plutonium analyses were performed a tVER L, 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 i s 0.4 pCi/ml for five ml of recovered water. At this concentration the error term f o r the 2 sigma confidence level i s k 100 percent. Analyses of the coconut milk and soil samples indicated the concentrations o f tritium were less than the minimum detectable level. P1 utoni u m analyses which were performed on soi 1 samples were by radiochemical separation followed by pulse height analysis using a lithium-drifted silicon The analytical error associated with the results for plutonium on prefi 1ters i s approximately t 25% a t the 2 sigma confidence level. Unless otherwise specified each soil sample represented the t o p one t o two inches of a one-square-foot area a t each location. gamma ray spectrum analysis was performed t o identify the most abundant radionuclides and t o estimate their relative contribution t o the total activity. The analytical error i s approximately ten t o fifteen percent.

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The island of Bikini i s the largest in the atoll,having an area of about0.6 square miles and has traditionally been the "home island" of the Bikinians. Individual land rights extend from the lagoon t o the ocean. I t is anticipated that the villaoe will be rebuilt along the lagoon shore with comnunity buildings heina located about midway along the length. The island was prepared f o r agricultural redevelopment b y cutting parallel s t r i p s through the vegetation along the length of the island. The striDs, cut.on 56-foot centers, were approximately 20 f e e t wide. cover was knocked down and left in place t o provide additional organiG matter for the soil. The strips were surveyed and background gamma radiation levels recorded a t 250-foot intervals along their lenath. Figure 2illustrates the background variation by depicting the range and …