Letter to J W Thiessen, Subject: Facts About " Protracted Exposure to Fallout: the Rongelap and Utirik Experience " (Enclosures)

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j “:’ 3 “~ ASSOCIATED UNIVERSITIES, INC. U.S. Department of Energy Office of Health & Environmental Enclosed please find a copy of “Protracted Exposure to Fallout: The Rongelap and Utirik Experience” and a draft of “Thyroid Absorbed Dose For Rongelap and Utirik Residents”. The protracted exposure document was accepted by Health Physics. I have recently retuned the proofs to the Health Physics Journal and I anticipate it to be published within a few months. The draft document on thyroid absorbed dose has not been peer reviewed, and only two sections of the four section report are included. I am sending it to you because it is a tabulation of information pertinent to the activities of the Litigation Support Working Group. Please excuse any omissions, errors or unit inconsistencies in this draft. In response to your question about future activities in the Marshall Islands, I am enclosing a detailed five-year plan (1985 through 1989). This plan was prepared several weeks ago for Roger Ray in response to a list of questions set forth by the DOE Marshall Islands Planning Group. I feel these documents will be useful to the members of the working group and any comments will be appreciated.

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THYROID ABSORBED DOSE FOR RONGELAP AND UTIRIK RESIDENTS Safety and Environmental Protection Division Brookhaven National Laboratory Associated Universities, Inc. Under Contract No. DE-AC02-76CHOO016 with the United States Department of Energy.

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Since March 1954, persons who were present at Rongelap Island, Rongelap Atoll, Sifo Island, Ailinginae Atoll and Utirik Island, Utirik Atoll in the Marshall Islands have been examined by medical specialists to determine if any the Pacific weapon occurred as a result of test known as Operation exhibited over a period exposure to radioactive fallout from Castle ”BRAVO. Studies indicated of many months and possible long-term effects exhibited over many years. In order to estimate the risk of possible radiation induced thyroid effects, a study was undertaken to refine thyroid absorbed dose estimates for people at Rongelap, Sifo and Utirik Islands using four approaches: (1) relating radiochemical analysis data on March 1954 pooled urine to current intake, retention and excretion models in order to determine 1-131 inhaled or ingested, (2) estimating airborne concentrations and areal activities of the iodine isotopes from neutron irradiation studies on archival soil samples, (3) airborne concentrations and areal activities of the iodine isotopes derived from sourcs term, weather data and current computer models which predicted atmospheric diffusion and fallout deposition and (4) determining fallout components based on Bikini Ash, the radioactive fallout which fell on a Japanese fishing vessel in the vicinity of Rongelap Island. Bikini Ash was also used to derive air, water and surface activities of fallout nuclides. This re-examination resulted ia a greater man factor of 4) over that estimated by James roid absorbed dose due to a wide range of (Ja64). A wide range of possible thyactivity intake was also a result. Direct inhalation and ingestion of contaminated water were pathways which contributed in a minor way to fallout activity intake. The pathway contributing to most of the intake was fallout debris falling directly on food prepared and

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consumed outdoors during passage of the fallout cloud. The adult mean thyroid absorbed doses at Rongelap and Utirik were 13 and 1.7 grays respectively. The child mean thyroid absorbed doses were 40 grays at Rongelap and 4.9 grays at Utirik. The overall mean cancer risk in the exposed population of 251 people was 1.1 thyroid cancers per 10,000 people per gray per year. The mean time at risk for cancer was 18 years. The overall mean nodule risk was 8.4 nodules per 10,000 people per gray per year and the mean time at risk for nodules was also

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Methods and Results.............................................. 1-131 Thyroid Burden at Rongelap Island Based on Urine Radioiodine Air Concentrations Based on Meteorological Data and Source Term Data.................................. Radioiodine Surface Activity Based on Archival Soil Thyroid Absorbed Dose Estimate Based on Bikini Ash Results and Results from I, II, and III.................... A. Surface Radioactivity And Exposure Rate Estimates...... B. Radioactivity In Food, Water Supplies and Air .......... c. Absorbed Dose for Individuals..........................

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The authors fully appreciate the fine efforts of Nathanial A. Greenhouse of Lawrence Berkeley Laboratory, Lee V. Kaplan, a student from Yale University, Dr. Fred Brauer of Battelle Lawrence Livermore National Pacific Northwest Laboratory, Kendall Peterson of Laboratory, Dr. Charles Sondhaus of the University Conard, M.D., Eugene Cronkite, M.D., Andrew Hull, and Charles Meinhold all from Brookhaven National Laboratory and Dr. Bruce Wachholz from Depart~nt of Energy Headquarters in helping to prepare a scientific document. We gratefully acknowledge their contributions of ideas and procedures. We are also grateful to a number of colleagues who have read the manuscript for this report and offered valuable comments: William Adams, M.D. of Brookhaven National Laboratory, Dr. William Bair and Dr. Richard Gilbert of Battelle Pacific Northwest Laboratory, Dr. Roger McClellan of tion Toxicology Research Institute, and Dr. Jack Healy of Los

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1. 1-131 THYROID BU~EN AT RONGELAP ISLAND BASED ON URINE B.IOASSAY Urine .samples for 24-hour elimination were pooled and collected on the 17th day post detonation from persons evacuated from Rongelap Island (C072). The urine was sent to Los Alamos Scientific Laboratory and an estimate of thyroid absorbed dose from internal emitters was reported by Cohn (Cr56). The 64-person composite urine sample was 75% adult urine (18 L, >16 years of age), 20% adolescent urine (4.8 k, 5-16 years of age) and 4.8% child urine (1.2 L, <5 years of age) (Ja64). The adult mean peak thyroid content of 1-131 was estimated by Harris to be 11.2 pCi (Iia54). This estimate was based on the assumption that 0.1% of stable iodine intake on the first day would be eliminated via the urine between the 15th and 17th days (c072). Harris indicated a mean activity of 1.31 x 10 VCi of 1-131 in the Rongelap adult 24-hour urine taken on the 17th day Table 1 is a tabulation of the fraction of an initial 1-131 activity intake by ingestion that would be eliminated by an adult on a given day post the intzkz. These daily fractions were calculated by two methods, one was a model by Johnson (J081, see Fig. 1) and the other was a model used by ICRP (ICRP 30, see Fig. 2). Both nmdels incorporated feedback. Both were solved using catenary compartment kinetics and both led to similar values for elimination by a reference man (see Table 1). A comparison to an excretion curve in a normal adult male was made and values tabulated for the case of stable iodine (see Table 1). Values for female individuals may be slightly higher or equivalent as indicated by the comparison between reference male and female values. On the basis of 1.31 x 10-2 pCi in adult urine on the 17th day post intake, a 93 pCi intake was estimated for 1-131. Ingestion was assumed to occur

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at 0.5 days post detonation at Rongelap Island and elimination was assumed to occur between the begining and the end of the 17th day post detonation.

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Fraction of Initial 1-131 Activity Inges ~ That is Excreted On Given Day Post Intaket? Days Post Reference Reference Reference Fraction of Stable Iodine Ingested That Is Excreted on a Given Day Post Intake for a Normal Adult Male Days Post Reference kference A Normal (3) Berman (Be67), read from graph.

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IV. THYROID ABSORBED DOSE ESTIMATE BASED ON BIKINI ASH AND RESULTS FROM I, II AND III. A. Surface Activity And Exposure Rate Estimates 1. The Nuclide Composition Radiochemical analysis results for the BRAVO fallout were sunxnarizedin Table 1. Bikini Ash, the name of BRAVO fallout given by Yamatera and Tsuzuki (Ya56, Ts56), fell on the Japanese fishing vessel, the 5th Lucky Dragon, on the day of the test. Gross beta activity of Bikini Ash was measured and standardized to day 26 and individual nuclide beta-activity identified and quantified by Japanese-scientists. The per cent fission product beta activity expected on day 26 after formation was tabulated in Table 1. The expected beta activity was based on a fallout composition which was unaltered due to chemical or physical mechanisms affecting certain fission product nuclides. This unaltered composition was referred to as unfractionated. This unfractionated composition was calculated from data given by Crocker (Cr65). The comparison betwee~ the measured values of Bikini Ash beta activity and per cent unfractionated fission product beta activity required conversion of the Yamatera and Tsuzuki data sets into per cent fission product beta activity, that is, exclusion of the beta activity of the activation products S-35, Ca-45 and the transuranic nuclide U-237. It was assumed that u-237 which represented 20% of the beta activity on day 26 in the Tsuzuki data also represented 20% of the beta activity in the Yamatera data. The data in Table 1 headed “U-238TN Unfractionated % Fission Product Beta Activity” represented the day 26 theoretical per cent of selected unfractionated fission products following thermonuclear neutron fission of U-238. This tieutronenergy spectrum and uranium target were chosen to represent the BR4V0 device (OC68). The difference between Japanese

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=asurements and the expected beta activity data given in Table 1 represented differences between fractionated and unfractionated fallout. As previously implied, the term fractionation indicated alterations of nuclide composition in fallout debris. The ratio of two nuclides in fallout was often used to describe fractionation quantitatively (Fr61). The denominator of the ratio was taken to be the activity of ZrNb-95 (Fr61). To quantify fractionation between two nuclides the beta activity ratios were compared. The term “degree of fractionation” represented the range of variability of the nuclide ratio. The term “extent of fractionation” represented the portion of the total nuclide produced which departed from the unfractionated ratio. A review of the data in Table 1 indicated the nuclides’ Te-132t measured ZrNb-95 beta activity) did not differ by a factor greater than about 90, Ru-103 and Pr-143 fractionated by about a factor of 2 relative to the unfractionated ratios and the nuclides Sr-89 and Te-129m-Te-129 fractionated by about a factor of 3 relative to the unfractionated ratios. The nuclides Y-91, greater abundance relative to unfractionated debris. The other nuclides were in Freiling (Fr61) indicated that the degree of fractionation from a surface burst could be significant. The extent of the fractionation throughout the debris was another variable he obsened to be significant. Freiling emphasized the high degree of fractionation between nuclides classified as volaand refractory for coral atoll surface bursts. Generalizations to be used much caution were made. Freili.ng,indicated that fractionation in general

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would decrease as device yield decreased. He also indicated fractionation would increase with depth, that is, air bursts would be less fractionated than surface bursts which would burst creating the be less fractionated than sub-surface bursts. From it could be cautiously expected that the high yield surface BR4V0 fallout caused a moderate to high degree of fractionation which occurred moderately to extensively throughout the debris. For the coral surface burst, Freiling observed that the ratio of Zr-95 to Sr-89 activity could be chosen as a representative measure of the overall degree of fractionation between refractory and volatile elements. This ratio was obsemed twice and had a value of 5 for a deep water surface burst of megaton range and a value of 100 for a coral surface burst (Fr61). The unfractionated value for this ratio on day 26 post detonation for thermonuclear neutron fission of u-238 was calculated to be 1.6 from data given by Crocker (Cr65). From the average of Yamatera and ...a~,J5for tlie degree of fractionation was Tsuzuki data, the calculated ratio of on day 26 was 4.8. This measured characteristic of a deep water surface burst of the megaton range, moderately but not highly fractionated. This moderate fractionation probably occurred to extensively throughout the fallout because of the large yield and surface location of the device (Fr61). , The effect of fractionation on decay rate is very complex ple obsenation of overall radioactive decay does not yield significant tion. Even so, the 300 miles away from rates from activity decay rate from widely distributed samples obtained the BR4V0 detonation site were similar as were the decay on different size fallout granules collected at the same facts alone may not be used to indicate the same fractionation was coxmuonto all granule sizes. In fact, small granules traveled

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with the cloud for longer periods of time and possibly absorbed more longerlived nuclides than did the very large granules. In the forthcoming analysis, the fractionation observed for Bikini Ash granules was assumed to be similar for granules at Rongelap, Sifo and Utirik Islands. With the possible exception of Utirik Island, this was considered a value assumption due to the proximity of Sifo Islands to the 5th Lucky Dragon. The Decay of Fallout The gamma and beta decay of the BRAVO radioactivity after the first 10 days post detonation was measured by many researchers (e.g. Miller, Servis, Tomkins, Wilsey and Stetson, see 0C68).- Decaj data measured prior to 10 days was not found in the literature. Fallout samples, taken weeks after the BRAVO event, were from Bikini Atoll, Rongelap Atoll and from the surface of US Navy ships in the area. The measured decay exponent after two weeks was used by many researchers to extrapolate exposure rate back to times prior to sample collection and in one case was used to estimate activity decline detonation (Miller (OC68)). These calculations by Miller for out activity from several hours out to a few weeks post BRAVO every hour post the decay of fallexcluded the decay characteristics of non-fission nuclides. This would impact on surface activity estimates at the islands of interest since these estimates relied on extrapolated exposure rates. The thyroid dose from internal sources would be affected also by decay characteristics because it relied in part on surface activity estimates. In order to derive ground BRAVO detonation and to derive external activity estimates at times close to and internal thyroid dose, the gamma or beta decay rate decline over short periods of time was assumed to have followed the relationship

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where xl = gamma or beta decay rate at time tl, and X2 = gamma or beta decay rate at time t2. During early times post BRAVO and for short time intervals of a few hours it seemed Miller’s decay exponents may have departed significantly from the standard value used for planning fallout activity decline (m = -1.2) and thus his tabulations described the early decay of BRAVO fallout adequately. These values for m at different times post detonation of BRAVO were listed in Table 2. The overall decay exponent calculated from Miller’s data for the period one hour to sixty days post detonation was -1.2 and agreed with the standard value used for decay of unfractionated fission products. Thus, the to non-fission nuclides was not folded into Miller’s study was needed to establish BRAVO decay (OC68). impact on exposure rate due tabulations and further Surveys performed by the crew members of the USS PHILIP, the ship dispatched to evacuate Rongelap Island, have recorded an exposure …