Evaluation of the Radiological Quality of the Water on Bikini and Eneu Islands in 1975: Dose Assessment Based on Initial Sampling

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EVALUATION OF TU€ RADIOLOGICAL QUALITY OF TU€ WATER ON BIKINI AND ENEU ISLANDS IN 1975: DOSE ASSESSMENT BASED ON INITIAL SAMPLING Prepared for U.S. Energy Research & Development Administration under contract No. W-7405-Eng-48

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LAWRENCE LIVERMORE IABORATORY EVALUATION OF THE RADIOLOGICAL QUALITY OF THE WATER ON BIKINI AND ENEU ISLANDS IN 1975: DOSE ASSESSMENT BASED ON INITIAL SAMPLING

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Field Operations. Observations. and Procedures ..............2 Water Quality Standards ......................... 13 Bikini Island Cistern Water .......................2 Eneu and Bikini Groundwater ....................... 11 Eneu Island: Radionuclides .................... 14 Bikini Island: Radionuclides ................... 15

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EVALUATION OF THE RADIOLOGICAL QUALITY OF THE WATER ON BIKINI A N D ENEU ISLANDS IN 1975: DOSE ASSESSMENT BASED ON INITIAL SAMPLING In June of 1975 w e conducted asur - vey to determine the residual radio - activity in the terrestrial en v iron - ment on the two main islands (Eneu and Bikini) of Bikini Atoll. Our objec - ti ve was to evaluate the potential radiation doses that could be received by the Rik in ian s scheduled to return to their atoll. This report describes the radiological quality of the groundwater during June 1975 (from data obtained from water samples collected atold and new well sites on both islands) and the cistern water on Bikini Island. Based on analyses of these samples, w e found that the cistern water from Bikini Island is both chemically and radio logically acceptable as drinking water i n accordance with standard limits established by the U.S. Public Health Service. However, on both islands the quality of the groundwater varies from one site to another. A t some wells both chemical and radiological quality are acceptable ; at others one or both are unacceptable according to U.S. Public Health Standards. The doses we predict from consumption of both cistern and groundwater are acceptable under federal guidelines. However, doses predicted from consumption of groundwater are high enough to warrant careful evaluation of other potential To evaluate the potential radiation measuring environmental gamma-ray exposure rates and collecting samplesd oses that could be received by Bikini an s returning to their atoll, of soil, groundwater, cister-rt water, w e conducted a survey during June 1375 to determine the residual radio - activity in the terrestrial environ- food chains. ment on Bikini and Eneu Islands of Bikini Atoll. The survey included logical quality of the groundwater and vegetation to use in assessing the internal doses from pertinent This report describes the radio -

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during June 1975, based on data obtained from water samples collected atold and new well sites on the islands. We also include results on the radio nuclide levels in three rainwater cisterns on Bikini Island. Doses are calculated assuming water consumption from both cistern and The chemical and radiological quality of the water i s compared t o standards established by theU.S. Public Health Service and tothe recommended maximum permissible water concentrations from Federal Radiation Council (FRC) part 20 standards for protection against We are presently evaluating the radio nuclide and elemental content of groundwater samples collected from these wells in January of 1977. This will allow usto assess the temporal changes which may have resulted from disturbance of normal groundwater concentrations following the initial drilling of the wells. Field Operations, Observations, and Procedures quality over as large an area as possible. We had planned toes tab - li sh additional wells in the south - ern parts of Bikini and Eneu but were unable todo so because of The wells were started by @?tab vat in gap it with a backhoe tothe depth of the groundwater surface. te red at HFH 2(2.7m below ground rock layers were not encomitered a% loosen the coral aggregate bb-elov tke water surface to as great a depktr as physically possible, and slotted

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Second basel ine north baseline north Bikini Island Fig. 1. Locations of wells on Bikini (upper) and Eneu (lower) Islaqdc. An asterisk indicates that the building had an associated rainwater cistern that was sampled.

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the hole. The pipe was capped atthe bottom to prevent soil from filling the interior of the pipe. The slots above the waterline were taped over to prevent surface debris from enter - ing the casing from above. was back filled with the excavated soil,with the removed bottom soil being returned to the pit first. Table1gives the depth to which the slotted casing extends below the surface of the water table and the depth of the water table below ground surface. Most of these water depths were measured during periods of lowest tide, We detected no differences in conductivity throughout the accessib le length of each water column. The thickness of the freshest water layer at each location is a t least equivalent to the water depths in Before the water inthe wells was sampled, i t was allowed to stabilize for one t o two days. The entire pumping system was purged with at least 100 litres of water from any respective well, and all collection containers were thoroughly rinsed to samples. Samples were withdrawn by through a section of flexible plastic tubing lowered into the pipe below the water surface. The pumping rate could be regulated by a variable - speed control over the range from a few millilitres per minute to8 litres per minute. Conductivity was

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radionuclide samples or stab Ie -e Iem ent and nutrient sam pl es Fig. 2. Diagram of the pump arrangement for collection of groundwater samples. monitored during pumping by channel- analysis of chlorin it y and other ing the water through an inline con- constituents. duct iv it y meter. The water then In an experiment we designed to passed through two filters (1-pm and follow the chemical and radiological 0.4-pm) t o remove suspended part icu - changes inthe water resulting from late material ; these filters were continuous pumping ata cxmstant subsequently analyzed for radio - rate, groundwater a t HFH 1 was nuclide content. The filtrate was pumped out continuously over an 8-hr ,collected for radio nuclide analysis period ; a total of 3200 litres was smaller volumes were collected for duct iv it y was monitored throughout

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the entire test, and samples were collected for analysis at the start, midpoint, and end of the test.If the mean daily water consumption rate by humans is assumed t o be 2litres per day,the total volume removed was equivalent to what could have been used by 100 people in16 days. The usable groundwater is therefore a valuable resource to the people of A similar test was conducted a t FWR 1 on Eneu, but only 2400 litres ing period. Samples were taken at the beginning and end of this test. The conductivity of the water during the pumping operations at these two wells is shown inFig.3, which also relates conductivity to the time of We also obtained a 15-gal filtered water sample from the old Bikini well (HFH 7). From our discussions with the Bikini people as well as from our own observations,we learned that large quantities of the groundwater from this well are being withdrawn almost daily for crop irrigation. This water has also been used for drinking during periods of drought. Large-volume samples were also pumped from the two old wells on Eneu (FWR 3 and 4 ) and from three rainwater cisterns sampled on Bikini Island .t 4 Sample Sample Sample Fig. 3. Inline conductivity vs volume pumped for wells Well FWR 3 had been drilled and cased to a depth of 13 m below ground level. No record can b e found to indicate why o r when this well was established.A salinity profile of the water column (Fig.4) showed the upper, fresher layer to be approximately 2m thick. Below itthe salinity rapidly increased in ahtiit linear fashion - tothe bottom. A the surface layer ; no change i n water casing must be slotted in some manner

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Salinity - parts per thousand Fig. 4. Salinity profiles of groundwater column at to permit rapid horizontal recharge. The bottom water, of course, was brackish and smelled very strongly of hydrogen sulfide; it contained a considerable amount of black suspended material of unknown composition. All of the 15-gal water samples were returned to the Lawrence Livermore Laboratory for processing. (The samples for chemical analysis were sent to Dr. R. Buddemeier at the University of Hawaii.) ration technique was used to isolate nuclides from all samples regardless of water salinity. Standardized mixed carrier solutions (containing stable carriers of Cs, Sr, Coy Bi, Sb, rare earths, and either 242Pu or 236Pu and 243Am) were added to the acidified samples. The radionuclides were separated from the water and the suspended samples using a pubtions. A complete description of these modifications and our newer separation technique is in press.7 Precipitation from the water samples with ferric hydroxide or manganese dioxide scavenged any plutonium radioor rare-earth radionuclides. This precipitate was then counted on lowlevel gamma spectrometers for quantitative assay of the latter gammaemitting radionuclides in the sample.- detected at levels above our lowest tively, for those radionuclides. The filter samples were dry-ashed and counted on gamma spectrometers; only 137Cs was detected. The other gamma-emitting radionuclides in the particulate phase were below the limits listed above. The ashed ff lter s were then processed to separate and analyze Pu No attempt was made to separate emitting radionuclides such as 147P~ sent in environmental samples from

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Water Quality Standards The sections that follow give Chloride 250 mgll general descriptions of our chemical Nitrate and radiological results. Before Total dissolved our results could be compared, w e 500 mg/ls olids needed to define a standard for the freshness of the water. We use,but only as a guide and reference for the Public Health Service. The following two paragraphs are quoted from Public Health Service Publication 956. (a) The following chemical substance should not be present ina water supply in excess of the listed concentrations when other more suitable supplies are o r can be made available : (b) The Advisory Committee, in considering limits which should be established for drink - ing water, recommended limits for only two of the above supplies shall be approved without further consideration of other sources of radioactivity in take of Radium-226 and contains these substances in amounts n o t exceeding 3 and Bikini Island Cistern Water Unfiltered water samples were collected on June 21, 1975, from the rainwater cisterns connected t o Bldgs. 5 and 24 and the school on Bikini Island. The available chemical and radiological data from these samples are given in Table2. The data summarized in the table indicate that the water appears to be chemically adequate € or drinking well as suitable for any household o r fate concentrations are well below the limits established for drink € e g water by the U.S. Public Health Service. The total coliform conterut of the water was not determined. The measured radio nuclides were also low in concentration in these tions are roughly two to three times pCi / litre in New York City tap water'' but are equivalent Ca the average New York City tap water concent rations measured during the peak fallout years of 1963-1966. The

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Table2.Analytical data from cistern water sampled on June 21, 1975, on Bikini a The values in parentheses are the 1-u counting errors expressed as percentages of the listed values. present levels are also similar t o the 1971-1973 water concentrations i n Lake Ontario.12 These present levels of in the Bikini wells are less than 20% of the drinking - water limit of 10 pCi / li trees tab - li shed by theU.S.Public Health Service for domestic supplies and are 0.4% of the FRC limit of 300 higher than the 1974 tap water concent rations for New York City but are only 0.01% of the maximum permiss i ble concentration of 20 nCi/ litre based on FRC guidelines. average concentration of in the cistern water is less than 0.0003% of the FRC concentration average 239 9240 ~ uc on cent ration of 17fCi / litre in the cistern water is greater than the average surface groundwater concentrations at Eneu average concentration (44 fc il litre) in Bikini surface groundwater. Examination of the radio nuclide concentrations in the cistern water and comparisons with other data reveal that the largest percentage of the radioactivity in the water sources other than worldwide fallout. Consider first that the 137Cs1 S r ratio varies between 0.93 and 2.27 in the three samples. One would expect that fallout depositions of these two radio nuclides would b e

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much more uniform over the small areas encompassing the three build - in gs attached to the cisterns. cent rations in rainfall at several Pacific islands between 1968 and 1974. When the six - year mean values are plotted as a function of latitude, the interpolated mean quantity of fallout expected in rainwater at the latitude of Bikini Atoll is have, on the average, 15 times this were constructed after 1969, w e can only conclude that fallout 'OS,, and tribute only a small percentage to the levels of those radio nuclides found in the cistern samples. As additional support for this argument, water samples from the drinking water tanks of theL.C.U. support boat R. V.L ikta nur used during this expedition to Bikini have been analyzed for 137Cs and 239 ~ 240Pu. This drinking water i s derived from rainwater catchment systems at Kwajalein Atoll. During October 1975 this freshwater convalues are thus representative of the fallout levels in rainfall in the Marshall Islands. The and 137Cs levels in this water are