C. L. Conrado

Lawrence Livermore National Laboratory, Livermore, California, United States

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Publications (29)20.21 Total impact

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    ABSTRACT: Coconut trees growing on atolls of the Bikini Islands are on the margin of K deficiency because the concentration of exchangeable K in coral soil is very low, ranging from only 20 to 80mgkg(-1). When provided with additional K, coconut trees absorb large quantities of K and this uptake of K significantly alters the patterns of distribution of 137Cs within the plant. Following a single K fertilization event, mean total K in trunks of K-treated trees is 5.6 times greater than in trunks of control trees. In contrast, 137Cs concentration in trunks of K-treated and control trees is statistically the same while 137Cs is significantly lower in edible fruits of K-treated trees. Within one year after fertilization (one rainy season), K concentration in soil is back to naturally low concentrations. However, the tissue concentrations of K in treated trees stays very high internally in the trees for years while 137Cs concentration in treated trees remains very low in all tree compartments except for the trunk. Potassium fertilization did not change soil Cs availability. Mass balance calculations suggest that the fertilization event increased above ground plant K content by at least a factor of 5 (2.2kg). Potassium concentrations and content were higher in all organs of K-fertilized trees with the greatest increases seen in organs that receive a portion of tissue K through xylem transport (trunk, fronds and fruit husks) and lowest in organs supplied predominantly with K via the phloem (palm heart, spathe, coco meat and fluid). The 137Cesium concentrations and contents were dramatically lower in all organs of K-treated trees with greatest proportional reductions observed in organs supplied predominantly with K via the phloem (palm heart, spathe, coco meat and fluid). All trees remobilize both K and 137Cs from fronds as they proceed toward senescence. In control trees the reduction in concentration of K and 137Cs in fronds as they age is logarithmic, but K remobilization is linear in K-treated trees where K concentration is high. As a result of K treatment the 137Cs concentration in K-treated fronds is extremely low and constant with frond age. Fronds of K-treated trees contain a greater amount of K than control tree fronds. As they fall to the ground and decay they provide a small continuing pool of K that is about 3% of the natural K in soil under the tree canopy. Results of K and 137Cs concentration and distribution in control and K-treated coconut trees suggest that the application of K reduces 137Cs uptake both in the short term immediately following K fertilization and in the long term, after soil K levels have returned to normal but while plant K stores remain high. These results suggest that high internal K concentration and not high soil K is primarily responsible for long-term reduction of 137Cs in edible fruits, play a significant role in limiting further uptake of 137Cs by roots, and affects allocation of 137Cs to edible fruits for years. Coconut trees are capable of luxury K accumulation when provided with excess K and in this example the additional K can effectively provide the K requirements of the plant for in excess of 10y. The reduction of 137Cs uptake lasts for at least 10y after K is last applied and greatly reduces the estimated radiation dose to people consuming local tree foods. Effectiveness and duration of K treatment provide important assurances that reduction in 137Cs is long term and the radiation dose from consuming local plant foods will remain low.
    Journal of Environmental Radioactivity 01/2009; 100(1):76-83. DOI:10.1016/j.jenvrad.2008.10.016 · 3.57 Impact Factor
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    ABSTRACT: Inter-plant concentration ratios (IPCR) [Bqg(-1)(137)Cs in coral atoll tree food crops/Bqg(-1)(137)Cs in leaves of native plant species whose roots share a common soil volume] can replace transfer factors (TF) to predict (137)Cs concentration in tree food crops in a contaminated area with an aged source term. The IPCR strategy has significant benefits relative to TF strategy for such purposes in the atoll ecosystem. IPCR strategy applied to specific assessments takes advantage of the fact that tree roots naturally integrate (137)Cs over large volumes of soil. Root absorption of (137)Cs replaces large-scale, expensive soil sampling schemes to reduce variability in (137)Cs concentration due to inhomogeneous radionuclide distribution. IPCR [drinking-coconut meat (DCM)/Scaevola (SCA) and Tournefortia (TOU) leaves (native trees growing on all atoll islands)] are log-normally distributed (LND) with geometric standard deviation (GSD)=1.85. TF for DCM from Enewetak, Eneu, Rongelap and Bikini Atolls are LND with GSDs of 3.5, 3.0, 2.7, and 2.1, respectively. TF GSD for Rongelap copra coconut meat is 2.5. IPCR of Pandanus fruit to SCA and TOU leaves are LND with GSD=1.7 while TF GSD is 2.1. Because IPCR variability is much lower than TF variability, relative sampling error of an IPCR field sample mean is up 6- to 10-fold lower than that of a TF sample mean if sample sizes are small (10-20). Other IPCR advantages are that plant leaf samples are collected and processed in far less time with much less effort and cost than soil samples.
    Journal of Environmental Radioactivity 02/2008; 99(1):181-9. DOI:10.1016/j.jenvrad.2007.08.004 · 3.57 Impact Factor
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    ABSTRACT: Bikini Island was contaminated on March 1, 1954 by the Bravo detonation (U.S. nuclear test series, Castle) at Bikini Atoll. About 90% of the estimated dose from nuclear fallout to potential island residents is from cesium-137 ((137)Cs) transferred from soil to plants that are consumed by residents. Thus, radioecology research efforts have been focused on removing (137)Cs from soil and/or reducing its uptake into vegetation. Most effective was addition of potassium (K) to soil that reduces (137)Cs concentration in fruits to 3-5% of pretreatment concentrations. Initial observations indicated this low concentration continued for some time after K was last applied. Long-term studies were designed to evaluate this persistence in more detail because it is very important to provide assurance to returning populations that (137)Cs concentrations in food (and, therefore, radiation dose) will remain low for extended periods, even if K is not applied annually or biennially. Potassium applied at 300, 660, 1260, and 2070 kg ha(-1) lead to a (137)Cs concentration in drinking-coconut meat that is 34, 22, 10, and about 4% of original concentration, respectively. Concentration of (137)Cs remains low 8-10 y after K is last applied. An explanation for this unexpected result is discussed.
    Journal of Environmental Radioactivity 02/2006; 88(3):251-66. DOI:10.1016/j.jenvrad.2006.02.007 · 3.57 Impact Factor
  • W Robison, C Conrado, S Kehl
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    ABSTRACT: Cesium-137 was deposited on Bikini Island at Bikini Atoll in 1954 as a result of nuclear testing and has been transported and cycled in the ecosystem ever since. Atoll soils are of marine origin and are almost pure CaCOâ with high concentrations of organic matter in the top 40 cm. Data from previous experiments with mature fruit trees show very high transfer factors (TF's), [Bq g⁻¹ plant/ Bq g⁻¹ soil, both in dry weight] into fruits from atoll calcareous soil. These TF's are much higher than reported for continental, silica-based soils. In this report TF's for 5 types of leafy vegetable crops and 2 types of grain crops are provided for use in predictive dose assessments and for comparison with other data from other investigators working with other types of soil in the IAEA CRP ''The Classification of Soil Systems on the Basis of Transfer Factors of Radionuclides from Soil to Reference Plants''. Transfer factors for plants grown on calcareous soil are again very high relative to clay-containing soils and range from 23 to 39 for grain crops and 21 to 113 for leafy vegetables. Results from these experiments, in this unique, high pH, high organic content, low potassium (K) soil, provide a boundary condition for models relating soil properties to TF.
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    ABSTRACT: The United States (US) conducted nuclear weapons testing from 1946 to 1958 at Bikini and Enewetak Atolls in the northern Marshall Islands. Based on previous detailed dose assessments for Bikini, Enewetak, Rongelap, and Utirik Atolls over a period of 28 years, cesium-137 (137Cs) at Bikini Atoll contributes about 85-89% of the total estimated dose through the terrestrial food chain as a result of uptake of 137Cs by food crops. The estimated integral 30, 50, and 70-year doses were based on the radiological decay of 137Cs (30-year half-life) and other radionuclides. However, there is a continuing inventory of 137Cs and 90Sr in the fresh water portion of the groundwater at all contaminated atolls even though the turnover rate of the fresh groundwater is about 5 years. This is evidence that a portion of the soluble fraction of 137Cs and 90Sr inventory in the soil is lost by transport to groundwater when rainfall is heavy enough to cause recharge of the lens, resulting in loss of 137Cs from the soil column and root zone of the plants. This loss is in addition to that caused by radioactive decay. The effective rate of loss was determined by two methods: (1) indirectly, from time-dependent studies of the 137Cs concentration in leaves of Pisonia grandis, Guettarda specosia, Tournefortia argentea (also called Messerschmidia), Scaevola taccada, and fruit from Pandanus and coconut trees (Cocos nucifera L.), and (2) more directly, by evaluating the 137Cs/90Sr ratios at Bikini Atoll. The mean (and its lower and upper 95% confidence limits) for effective half-life and for environmental-loss half-life (ELH) based on all the trees studied on Rongelap, Bikini, and Enewetak Atolls are 8.5 years (8.0 years, 9.8 years), and 12 years (11 years, 15 years), respectively. The ELH based on the 137Cs/90Sr ratios in soil in 1987 relative to the 137Cs/90Sr ratios at the time of deposition in 1954 is less than 17 years. The magnitude of the decrease below 17 years depends on the ELH for 90Sr that is currently unknown, but some loss of 90Sr does occur along with 137Cs. If the 15-year upper 95% confidence limit on ELH (corresponding to an effective half-life of 9.8 years) is incorporated into dose calculations projected over periods of 30, 50, or 70 years, then corresponding integral doses are 58, 46 and 41%, respectively, of those previously calculated based solely on radiological decay of 137Cs.
    Journal of Environmental Radioactivity 02/2003; 69(3):207-23. DOI:10.1016/S0265-931X(03)00080-8 · 3.57 Impact Factor
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    ABSTRACT: The Lawrence Livermore National Laboratory has developed an extensive quality assurance program to provide high quality data and assessments in support of the Marshall Islands Dose Assessment and Radioecology Program. Our quality assurance objectives begin with the premise of providing integrated and cost-effective program support (to meet wide-ranging programmatic needs, scientific peer review, and build public confidence) and continue through from design and implementation of large-scale field programs, sampling and sample preparation, radiometric and chemical analyses, documentation of quality assurance/quality control practices, exposure assessments, and dose/risk assessments until publication. The basic structure of our radioassay quality assurance/quality control program can be divided into four essential elements: (1) sample and data integrity control, (2) instrument validation and calibration, (3) method performance testing, validation, development and documentation, and (4) periodic peer review and on-site assessments. While our quality assurance objectives are tailored towards a single research program and the evaluation of major exposure pathways/critical radionuclides pertinent to the Marshall Islands, we have attempted to develop quality assurance practices that are consistent with proposed criteria designed for laboratory accreditation.
    Journal of Radioanalytical and Nuclear Chemistry 01/2000; 243(2):415-422. DOI:10.1023/A:1016022029721 · 1.42 Impact Factor
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    ABSTRACT: The US conducted a series of nuclear tests from 1946 to 1958 at Bikini, a coral atoll, in the Marshall Islands (MI). The aquatic and terrestrial environments of the atoll are still contaminated with several long-lived radionuclides that were generated during testing. The four major radionuclides found in terrestrial plants and soils are Cesium-137 ({sup 137}Cs), Strontium-90 ({sup 90}Sr), Plutonium-239+240 ({sup 239+240}Pu) and Americium-241 ({sup 241}Am). {sup 137}Cs in the coral soils is more available for uptake by plants than {sup 137}Cs associated with continental soils of North America or Europe. Soil-to-plant {sup 137}Cs median concentration ratios (CR) (kBq kg{sup {minus}1} dry weight plant/kBq kg{sup {minus}1} dry weight soil) for tropical fruits and vegetables range between 0.8 and 36, much larger than the range of 0.005 to 0.5 reported for vegetation in temperate zones. Conversely, {sup 90}Sr median CRs range from 0.006 to 1.0 at the atoll versus a range from 0.02 to 3.0 for continental silica-based soils. Thus, the relative uptake of {sup 137}Cs and {sup 90}Sr by plants in carbonate soils is reversed from that observed in silica-based soils. The CRs for {sup 239+240}Pu and {sup 241}Am are very similar to those observed in continental soils. Values range from 10{sup {minus}6} to 10{sup {minus}4} for both {sup 239+240}Pu and {sup 241}Am. No significant difference is observed between the two in coral soil.
    12/1998
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    ABSTRACT: No abstract prepared.
    09/1997
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    Kenneth T. Bogen, Cynthia L. Conrado, William L. Robison
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    ABSTRACT: Uncertainty and interindividual variability were assessed in estimated doses for a rehabilitation scenario for Bikini Island at Bikini Atoll, in which the top 40 cm of soil would be removed in the housing and village area, and the rest of the island would be treated with potassium fertilizer, prior to an assumed resettlement date of 1999. Doses were estimated for ingested 137Cs and 90Sr, external gamma-exposure, and inhalation+ingestion of 241Am + 239+240Pu. Two dietary scenarios were considered: imported foods are available (IA); imported foods are unavailable with only local foods consumed (IUA). After approximately 5 y of Bikini residence under either IA or IUA assumptions, upper and lower 95% confidence limits on interindividual variability in calculated dose were estimated to lie within a approximately threefold factor of its in population-average value; upper and lower 95% confidence limits on uncertainty in calculated dose were estimated to lie within a approximately twofold factor of its expected value. For reference, the expected values of population-average dose at age 70 y were estimated to be 16 and 52 mSv under IA and IUA dietary assumptions, respectively. Assuming that 200 Bikini resettlers would be exposed to local foods (under both IA and IUA assumptions), the maximum 1-y dose received by any Bikini resident is most likely to be approximately 2 and 8 mSv under the IA and IUA assumptions, respectively. Under the most likely dietary scenario, involving access to imported foods, this analysis indicates that it is most likely that no additional cancer fatalities (above those normally expected) would arise from the increased radiation exposures considered.
    Health Physics 08/1997; 73(1):115-26. DOI:10.1097/00004032-199707000-00009 · 0.77 Impact Factor
  • W L Robison, K T Bogen, C L Conrado
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    ABSTRACT: On 1 March 1954, a nuclear weapon test, code-named BRAVO, conducted at Bikini Atoll in the northern Marshall Islands contaminated the major residence island. There has been a continuing effort since 1977 to refine dose assessments for resettlement options at Bikini Atoll. Here we provide a radiological dose assessment for the main residence island, Bikini, using extensive radionuclide concentration data derived from analysis of food crops, ground water, cistern water, fish and other marine species, animals, air, and soil collected at Bikini Island as part of our continuing research and monitoring program that began in 1978. The unique composition of coral soil greatly alters the relative contribution of 137Cs and 90Sr to the total estimated dose relative to expectations based on North American and European soils. Without counter measures, 137Cs produces 96% of the estimated dose for returning residents, mostly through uptake from the soil to terrestrial food crops but also from external gamma exposure. The doses are calculated assuming a resettlement date of 1999. The estimated maximum annual effective dose for current island conditions is 4.0 mSv when imported foods, which are now an established part of the diet, are available. The 30-, 50-, and 70-y integral effective doses are 91 mSv, 130 mSv, and 150 mSv, respectively. A detailed uncertainty analysis for these dose estimates is presented in a companion paper in this issue. We have evaluated various countermeasures to reduce 137Cs in food crops. Treatment with potassium reduces the uptake of 137Cs into food crops, and therefore the ingestion dose, to about 5% of pretreatment levels and has essentially no negative environmental consequences. We have calculated the dose for the rehabilitation scenario where the top 40 cm of soil is removed in the housing and village area, and the rest of the island is treated with potassium fertilizer; the maximum annual effective dose is 0.41 mSv and the 30-, 50-, and 70-y integral effective doses are 9.8 mSv, 14 mSv, and 16 mSv, respectively.
    Health Physics 08/1997; 73(1):100-14. DOI:10.2172/123199 · 0.77 Impact Factor
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    ABSTRACT: Fallout from atmospheric nuclear tests, especially from those conducted at the Pacific Proving Grounds between 1946 and 1958, contaminated areas of the Northern Marshall Islands. A radiological survey at some Northern Marshall Islands was conducted from September through November 1978 to evaluate the extent of residual radioactive contamination. The atolls included in the Northern Marshall Islands Radiological Survey (NMIRS) were Likiep, Ailuk, Utirik, Wotho, Ujelang, Taka, Rongelap, Rongerik, Bikar, Ailinginae, and Mejit and Jemo Islands. The original test sites, Bikini and Enewetak Atolls, were also visited on the survey. An aerial survey was conducted to determine the external gamma exposure rate. Terrestrial (soil, food crops, animals, and native vegetation), cistern and well water samples, and marine (sediment, seawater, fish and clams) samples were collected to evaluate radionuclide concentrations in the atoll environment. Samples were processed and analyzed for 137Cs, 90Sr, 239+240Pu and 241Am. The dose from the ingestion pathway was calculated using the radionuclide concentration data and a diet model for local food, marine, and water consumption. The ingestion pathway contributes 70% to 90% of the estimated dose. Approximately 95% of the dose is from 137Cs. 90Sr is the second most significant radionuclide via ingestion. External gamma exposure from 137Cs accounts for about 10% to 30% of the dose. 239+240Pu and 241Am are the major contributors to dose via the inhalation pathway; however, inhalation accounts for only about 1% of the total estimated dose, based on surface soil levels and resuspension studies. All doses are computed for concentrations decay corrected to 1996. The maximum annual effective dose from manmade radionuclides at these atolls ranges from .02 mSv y(-1) to 2.1 mSv y(-1). The background dose in the Marshall Islands is estimated to be 2.4 mSv y(-1). The combined dose from both background and bomb related radionuclides ranges from slightly over 2.4 mSv y(-1) to 4.5 mSv y(-1). The 50-y integral dose ranges from 0.5 to 65 mSv.
    Health Physics 08/1997; 73(1):37-48. DOI:10.1097/00004032-199707000-00004 · 0.77 Impact Factor
  • William L. Robison, Kenneth T. Bogen, Cynthia L. Conrado
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    ABSTRACT: There has been a continuing effort since 1977 to refine dose assessments for resettlement options at Bikini Atoll. Here we provide a radiological dose assessment for the main residence island, Bikini, using extensive radio nuclide concentration data derived from analysis of food crops, ground water, cistern water, fish and other marine species, animals, air, and soil collected at Bikini Island as part of our continuing research and monitoring program that began in 1978. The unique composition of coral soil greatly alters the relative contribution of ¹³⁷Cs and ⁹°Sr to the total estimated dose relative to expectations based on North American and European soils. Without counter measures, ¹³⁷Cs produces 96% of the estimated dose for returning residents, mostly through uptake from the soil to terrestrial food crops but also from external gamma exposure. The doses are calculated assuming a resettlement date of 1999. The estimated maximum annual effective dose for current island conditions is 4.0 mSv when imported foods, which are now an established part of the diet, are available. The 30-, 50-, and 70-y integral effective doses are 91 mSv, 130 mSv, and 150 mSv, respectively. A detailed uncertainty analysis for these dose estimates is presented in a companion paper in this issue. We have evaluated various countermeasures to reduce ¹³⁷Cs in food crops. Treatment with potassium reduces the uptake of ¹³⁷Cs into food crops, and therefore the ingestion dose, to about 5 % of pretreatment levels and has essentially no negative environmental consequences. We have calculated the dose for the rehabilitation scenario where the top 40 cm of soil is removed in the housing and village area, and the rest of the island is treated with potassium fertilizer; the maximum annual effective dose is 0.41 mSv and the 30-, 50-, and 70-y integral effective doses are 9.8 mSv, 14 mSv, and 16 mSv, respectively. 44 refs., 3 figs., 11 tabs.
    Health Physics 07/1997; 73(1):100-114. DOI:10.1097/00004032-199707000-00008 · 0.77 Impact Factor
  • K.T. Bogen, C.L. Conrado, W.L. Robison
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    ABSTRACT: A detailed analysis of uncertainty and interindividual variability in estimated doses was conducted for a rehabilitation scenario for Bikini Island at Bikini Atoll, in which the top 40 cm of soil would be removed in the housing and village area, and the rest of the island is treated with potassium fertilizer, prior to an assumed resettlement date of 1999. Predicted doses were considered for the following fallout-related exposure pathways: ingested Cesium-137 and Strontium-90, external gamma exposure, and inhalation and ingestion of Americium-241 + Plutonium-239+240. Two dietary scenarios were considered: (1) imported foods are available (IA), and (2) imported foods are unavailable (only local foods are consumed) (IUA). Corresponding calculations of uncertainty in estimated population-average dose showed that after {approximately}5 y of residence on Bikini, the upper and lower 95% confidence limits with respect to uncertainty in this dose are estimated to be approximately 2-fold higher and lower than its population-average value, respectively (under both IA and IUA assumptions). Corresponding calculations of interindividual variability in the expected value of dose with respect to uncertainty showed that after {approximately}5 y of residence on Bikini, the upper and lower 95% confidence limits with respect to interindividual variability in this dose are estimated to be approximately 2-fold higher and lower than its expected value, respectively (under both IA and IUA assumptions). For reference, the expected values of population-average dose at age 70 were estimated to be 1.6 and 5.2 cSv under the IA and IUA dietary assumptions, respectively. Assuming that 200 Bikini resettlers would be exposed to local foods (under both IA and IUA assumptions), the maximum 1-y dose received by any Bikini resident is most likely to be approximately 2 and 8 mSv under the IA and IUA assumptions, respectively.
  • W.L. Robison, C.L. Conrado, K.T. Bogen
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    ABSTRACT: We have updated the radiological dose assessment for Rongelap Island at Rongelap Atoll using data generated from field trips to the atoll during 1986 through 1993. The data base used for this dose assessment is ten fold greater than that available for the 1982 assessment. Details of each data base are presented along with details about the methods used to calculate the dose from each exposure pathway. The doses are calculated for a resettlement date of January 1, 1995. The maximum annual effective dose is 0.26 mSv y{sup {minus}1} (26 mrem y{sup {minus}1}). The estimated 30-, 50-, and 70-y integral effective doses are 0.0059 Sv (0.59 rem), 0.0082 Sv (0.82 rem), and 0.0097 Sv (0.97 rem), respectively. More than 95% of these estimated doses are due to 137-Cesium ({sup 137}Cs). About 1.5% of the estimated dose is contributed by 90-Strontium ({sup 90}Sr), and about the same amount each by 239+240-Plutonium ({sup 239+240}PU), and 241-Americium ({sup 241}Am).
  • W.L. Robison, C.L. Conrado, M.L. Stuart
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    ABSTRACT: This report is intended as a resource document for the eventual cleanup of Bikini Atoll and contains a summary of the data for the concentrations of /sup 137/Cs, /sup 90/Sr, /sup 239 +240/Pu, and /sup 241/Am in vegetation through 1987 and in soil through 1985 for 14 islands at Bikini Atoll. The data for the main residence island, Bikini, and the most important island, Eneu, are extensive; these islands have been the subject of a continuing research and monitoring program since 1974. Data for radionuclide concentrations in ground water, cistern water, fish and other marine species, and pigs from Bikini and Eneu Islands are presented. Also included are general summaries of our resuspension and rainfall data from Bikini and Eneu Islands. The data for the other 12 islands are much more limited because samples were collected as part of a screening survey and the islands have not been part of a continuing research and monitoring program. Cesium-137 is the radionuclide that produces most of the estimated dose for returning residents, mostly through uptake by terrestrial foods and secondly by direct external gamma exposure. Remedial measures for reducing the /sup 137/Cs uptake in vegetation are discussed. 40 refs., 32 figs., 131 tabs.
  • W.L. Robison, C.L. Conrado, W.A. Phillips
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    ABSTRACT: We have updeated the radiological dose assessment for Enjebi Island at Enewetak Atoll using data derived from analysis of food crops grown on Enjebi. This is a much more precise assessment of potential doses to people resettling Enjebi Island than the 1980 assessment in which there were no data available from food crops on Enjebi. Details of the methods and data used to evaluate each exposure pathway are presented. The terrestrial food chain is the most significant potential exposure pathway and /sup 137/Cs is the radionuclide responsible for most of the estimated dose over the next 50 y. The doses are calculated assuming a resettlement date of 1990. The average wholebody maximum annual estimated dose equivalent derived using our diet model is 166 mremy;the effective dose equivalent is 169 mremy. The estimated 30-, 50-, and 70-y integral whole-body dose equivalents are 3.5 rem, 5.1 rem, and 6.2 rem, respectively. Bone-marrow dose equivalents are only slightly higher than the whole-body estimates in each case. The bone-surface cells (endosteal cells) receive the highest dose, but they are a less sensitive cell population and are less sensitive to fatal cancer induction than whole body and bone marrow. The effective dose equivalents for 30, 50, and 70 y are 3.6 rem, 5.3 rem, and 6.6 rem, respectively. 79 refs., 17 figs., 24 tabs
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    ABSTRACT: This report is part of a continuing effort to refine dose assessments for resettlement options at Bikini Atoll. Radionuclide concentration data developed at Bikini Atoll since 1977 have been used in conjunction with recent dietary information and current dose models to develop the annual dose rate and 30- and 50-y integral doses presented here for Bikini and Eneu Island living patterns. The terrestrial food chain is the most significant exposure pathway--it contributes more than 50% of the total dose--and external gamma exposure is the second most significant pathway. Other pathways evaluated are the marine food chain, drinking water, and inhalation. Cesium-137 produces more than 85% of the predicted dose; /sup 90/Sr is the second most significant radionuclide; /sup 60/Co contributes to the external gamma exposure in varying degrees, but is a small part of the total predicted dose; the transuranic radionuclides contribute a small portion of the total predicted lung and bone doses but do present a long-term source of exposure. Maximum annual dose rates for Bikini Island are about 1 rem/y for the whole body and bone marrow when imported foods are available and about 1.9 rem/y when imports are unavailable. Maximum annual dose rates for Eneu Island when imports are available are 130 mrem/y for the whole body and 136 mrem/y for bone marrow. Similar doses when imported foods are unavailable are 245 and 263 mrem/y, respectively. The 30-y integral doses for Bikini Island are about 23 rem for whole body and bone marrow when imported foods are available and more than 40 rem when imports are unavailable. The Eneu Island 30-y integral doses for whole body and bone marrow are about 3 rem when imports are available and 5.5 and 6.1 rem, respectively, when imports are unavailable. Doses from living patterns involving some combination of Bikini and Eneu Islands fall between the doses listed above for each island separately.
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    ABSTRACT: A radiological survey was conducted in the Northern Marshall Islands to document reamining external gamma exposures from nuclear tests conducted at Enewetak and Bikini Atolls. An additional program was later included to obtain terrestrial and marine samples for radiological dose assessment for current or potential atoll inhabitants. This report is the first of a series summarizing the results from the terrestrial and marine surveys. The sample collection and processing procedures and the general survey methodology are discussed; a summary of the collected samples and radionuclide analyses is presented. Over 5400 samples were collected from the 12 atolls and 2 islands and prepared for analysis including 3093 soil, 961 vegetation, 153 animal, 965 fish composite samples (average of 30 fish per sample), 101 clam, 50 lagoon water, 15 cistern water, 17 groundwater, and 85 lagoon sediment samples. A complete breakdown by sample type, atoll, and island is given here. The total number of analyses by radionuclide are 8840 for /sup 241/Am, 6569 for /sup 137/Cs, 4535 for /sup 239 +240/Pu, 4431 for /sup 90/Sr, 1146 for /sup 238/Pu, 269 for /sup 241/Pu, and 114 each for /sup 239/Pu and /sup 240/Pu. A complete breakdown by sample category, atoll or island, and radionuclide is also included.
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    ABSTRACT: The purpose of this report is to refine the dose predictions, subsequent to the cleanup effort, for alternate living patterns proposed for resettlement of Enewetak Atoll. The most recent data developed from projects at Enewetak and Bikini Atolls for concentration and uptake of Cs, Sr, Pu, and Am were used in conjunction with recent dietary information and current dose models to predict annual dose rates and 30- and 50-y integral doses (dose commitments). The terrestrial food chain in the most significant exposure pathway - it contributes more than 50% of the total dose - and external gamma exposure is the second most significant pathway. Other pathways evaluated are the marine food chain, drinking water, and inhalation.
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    ABSTRACT: The United States (U.S.) Department of Energy (DOE) has recently implemented a series of strategic initiatives to address long-term radiological surveillance needs at former U.S. test sites in the Marshall Islands. The plan is to engage local atoll communities in developing shared responsibilities for implementing radiation protection programs for resettled and resettling populations. Using pooled resources of the U.S. Department of Energy and local atoll governments, individual radiation protection programs have been developed in whole-body counting and plutonium urinalysis to assess potential intakes of radionuclides from residual fallout contamination. The whole-body counting systems are operated and maintained by Marshallese technicians. Samples of urine are collected from resettlement workers and island residents under controlled conditions and analyzed for plutonium isotopes at the Lawrence Livermore National Laboratory (LNLL) using advanced accelerator based measurement technologies. This web site provides an overview of the methodologies, a full disclosure of the measurement data, and a yearly assessment of estimated radiation doses to resettlement workers and island residents.