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Four samples of archival Marshall Islands soil were subjected to non-destructive, broad energy (17 keV–2.61 MeV) gamma-ray spectrometry analysis using a series of different high-resolution germanium detectors. These archival samples were collected in 1967 from different locations on Bikini Atoll and were contaminated with a range of fission and activation products, and other nuclear material from multiple weapons tests. Unlike samples collected recently, these samples have been stored in sealed containers and have been unaffected by approximately 50 years of weathering. Initial results show that the samples contained measurable but proportionally different concentrations of plutonium, 241Am, and 137Cs, and 60Co.

A series of K d tracer batch experiments were conducted to assess the absorptive-desorption properties of Biochar as a potential agent to selectively sequester labile soil Cs or otherwise help reduce the uptake of Cs isotopes into plants. A parallel experiment was conducted for strontium. Fine-grained fractionated Woodlands tree Biochar was found to have a relatively high affinity for Cs ions (K d > 100) relative to coral soil (K d

By making modifications to our previously established measurement setup, we increased our abundance sensitivity for 233U by three orders of magnitude and can now measure 233U/238U ratios as low as 10−13. Because 233U has separate production pathways than 236U, it can provide valuable information on the particular source of anthropogenic uranium in a sample. We demonstrated the utility of our improved capability by using 233U to distinguish separate sources of anthropogenic uranium in a set of samples collected from a contaminated site. In the future, we plan to apply our new capability to characterizing 233U in a wide range of uranium materials.

Based on the encouraging results of our initial efforts to develop a 90Sr accelerator mass spectrometry capability, we have undertaken efforts to enhance our system. By changing some key operating parameters and constructing an optimized detector we were able to improve the discrimination of 90Sr from the isobaric interference 90Zr and reduce our instrumental background by nearly two orders of magnitude. Our current background (4 × 106 atoms, 3 mBq) is comparable to that achievable by decay counting, but is still a factor of ten higher than what is theoretically predicted based on the efficiency of our system. Therefore, future plans include implementation of a time-of-flight system to improve the rejection of 90Zr.

Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with 233U and 242Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA® column coupled to a UTEVA® column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of 234U/235U, 238U/235U, 236U/235U, and 240Pu/239Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment.

Plutonium-239 (239Pu) and plutonium-240 (240Pu) activity concentrations and 240Pu/239Pu atom ratios are reported for Brown Algae (Fucus distichus) collected from the littoral zone of Amchitka Island (Alaska), and at a control site at Unalaska, Alaska. The average 240Pu/239Pu atom ratio observed in dried F. distichus collected from Amchitka Island was 0.227 ± 0.007 (N = 5) and compares with the expected 240Pu/239Pu atom ratio in integrated worldwide fallout deposition in the Northern Hemisphere of 0.1805 ± 0.0057. In the absence of any evidence of a local source of plutonium containing an elevated 240Pu/239Pu isotopic signature, the characteristically high 240Pu/239Pu content of F. distichus supports the view of the existence of a discernible, basin-wide non-fallout source of plutonium entering the subarctic Pacific.

Runit Island on Enewetak Atoll was very heavily impacted by the U.S. nuclear testing campaign in the northern Marshall Islands (1946–58). The primary source of contamination on Runit Island was the 1958 Quince safety test where a large quantity of device plutonium (Pu) was scattered over the area near the GZ. A second low-yield device was detonated on the same site 10 days later, further disturbing the soil and leaving behind a very heterogeneous pattern of contamination including milligram-size particles of plutonium. A limited cleanup of the Fig-Quince zone was carried out in 1979. During this period, the effectiveness of the cleanup operations was primarily evaluated on the basis of bulk soil concentration data with little consideration given to the heterogeneity and long-term material-, biological-, and environmental-specific impacts of residual high activity (hot) particle contamination. The aim of the present study was twofold; (i) to characterize the levels and distribution of residual contamination in the Fig-Quince zone, and (ii) to develop pertinent data on the frequency distribution, elemental and isotopic composition, and physico-chemical properties of hot particles isolated from surface soils from Fig-Quince with a view towards providing recommendations on the future management and possible cleanup of the site. Today, Runit Island remains under an administrative quarantine.

Inter-plant concentration ratios (IPCR) [Bq g −1 137 Cs in coral atoll tree food crops/Bq g −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.

Major, minor and trace uranium isotopes were measured at Lawrence Livermore National Laboratory in environmentally acquired samples using different instruments to span large variations in concentrations. Multi-collector inductively-coupled plasma mass spectrometry (MC-ICPMS) can be used to measure major and minor isotopes: 238 U, 235 U, 234 U and 236 U. Accelerator mass spectrometry (AMS) can be used to measure minor and trace isotopes: 234 U, 236 U and 233 U. The main limit of quantification for minor or trace uranium isotopes is the abundance sensitivity of the measurement technique; i.e. the ability to measure a minor or trace isotope of mass M in the presence of a major isotope at M ± 1 mass units. The abundance sensitivity for 236 U/ 235 U isotope ratio measurements using MC-ICPMS is around ∼2 × 10 −6 . This compares with a 236 U/ 235 U abundance sensitivity of ∼1 × 10 −7 for the current AMS system, with the expectation of 2–3 orders of magnitude improvement in sensitivity with the addition of another high energy filter. Comparing 236 U/ 234 U from MC-ICPMS and AMS produced agreement within ∼10% for samples at 236 U levels high enough to be measurable by both techniques.

A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (40K, 60Co, 155Eu, 230Th, 238U, 238Pu, 239+240Pu and 241Am). Information values are given for 12 radionuclides (90Sr, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 232Th, 234U, 235U, 239Pu, 240Pu and 241Pu). Less reported radionuclides include 228Th, 236U, 239Np and 242Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units.

Six plutonium-containing particles stemming from Runit Island soil (Marshall Islands) were characterized by non-destructive analytical and microanalytical methods. Composition and elemental distribution in the particles were studied with synchrotron radiation based micro X-ray fluorescence spectrometry. Scanning electron microscope equipped with energy dispersive X-ray detector and with wavelength dispersive system as well as a secondary ion mass spectrometer were used to examine particle surfaces. Based on the elemental composition the particles were divided into two groups: particles with pure Pu matrix, and particles where the plutonium is included in Si/O-rich matrix being more heterogenously distributed. All of the particles were identified as nuclear fuel fragments of exploded weapon components. As containing plutonium with low 240Pu/239Pu atomic ratio, less than 0.065, which corresponds to weapons-grade plutonium or a detonation with low fission yield, the particles were identified to originate from the safety test and low-yield tests conducted in the history of Runit Island. The Si/O-rich particles contained traces of 137Cs (239 + 240Pu/137Cs activity ratio higher than 2500), which indicated that a minor fission process occurred during the explosion. The average 241Am/239Pu atomic ratio in the six particles was 3.7×10−3 ±0.2×10−3 (February 2006), which indicated that plutonium in the different particles had similar age. (Less)

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.

As a hard copy supplement to the Marshall Islands Program website (https://marshallislands.llnl.gov), this document provides an overview of the individual radiological surveillance monitoring program established in support of residents of Utrōk Atoll and nonresident citizens of the Utrōk Atoll population group, along with full disclosure of verified measurement data (2010-2012). The Utrōk Atoll Whole Body Counting Facility has been temporarily stationed on Majuro Atoll and, in cooperation with the Utrōk Atoll Local Government, serves as a national radiological facility open to the general public.

Accelerator mass spectrometry (AMS) is a sensitive and robust technique typically applied to the quantification of long-lived radioisotopes in samples too small to be decay-counted. AMS is characterized by a high rejection of interferences and a low susceptibility to matrix components, which reduce the demands on sample preparation chemistry. At Lawrence Livermore National Laboratory (LLNL), Center for Accelerator Mass Spectrometry (CAMS), we have developed an AMS capability for the measurement of actinide concentrations and isotopic ratios. To date, this capability has been primarily devoted to the measurement of 239Pu and 240Pu in bioassay and environmental samples including soils, sediments, waters, and human urine. For these analyses, a known amount of 242Pu is added to the samples as a reference isotope for normalization. Measurements of standard and intercomparison samples have shown that quantification is accurate and precise from at least 106 to 1011 atoms/sample. Recently, the ratios of 240Pu, 241Pu, 242Pu, and +Pu to intrinsic 239Pu have been successfully measured in soil samples from nuclear test sites. In addition, initial measurements of U and Np isotopes have yielded results consistent with the Pu measurements with respect to sensitivity, accuracy, precision, and linear range.

As a follow up to the initial 1998 intercomparison study, a second study was initiated in 2001 as part of the ongoing evaluation of the capabilities of various ultra-sensitive methods to analyze 239Pu in urine samples. The initial study1 was sponsored by the Department of Energy, Office of International Health Programs to evaluate and validate new technologies that may supersede the existing fission tract analysis (FTA) method for the analysis of 239Pu in urine at the µBq/l level. The ultra-sensitive techniques evaluated in the second study included accelerator mass spectrometry (AMS) by LLNL, thermal ionization mass spectrometry (TIMS) by LANL and FTA by the University of Utah. Only the results for the mass spectrometric methods will be presented. For the second study, the testing levels were approximately 4, 9, 29 and 56 µBq of 239Pu per liter of synthetic urine. Each test sample also contained 240Pu at a 240Pu/239Pu atom ratio of ~0.15 and natural uranium at a concentration of 50 µBq/ml. From the results of the two studies, it can be inferred that the best performance at the µBq level is more laboratory specific than method specific. The second study demonstrated that LANL-TIMS and LLNL-AMS had essentially the same quantification level for both isotopes. Study results for bias and precision and acceptable performance compared to ANSI N13.30 and ANSI N42.22 have been compiled.

Nuclear weapons tests conducted by the United States in the Marshall Islands produced significant quantities of regional or tropospheric fallout contamination. Here we report on some preliminary Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) measurements of plutonium isolated from seven composite soil samples collected from Bikini, Enewetak, and Rongelap Atolls in the northern Marshall Islands. These data show that 240Pu/239Pu isotopic signatures in surface soils from the Marshall Island vary significantly, and could potentially be used to help quantify the range and extent of fallout deposition (and associated impacts) from specific weapons tests. 137Cs and 60Co were also determined on the same set of soil samples for comparative purposes.

Mass spectrometric methods provide sensitive, routine, and cost-effective analyses of long-lived radionuclides. Here we report on the status of work at Lawrence Livermore National Laboratory (LLNL) to develop a capability for actinide measurements by accelerator mass spectrometry (AMS) to take advantage of the high potential of AMS for rejection of interferences. This work demonstrates that the LLNL AMS spectrometer is well-suited for providing high sensitivity, robust, high throughput measurements of plutonium concentrations and isotope ratios. Present backgrounds are ∼2 × 10 7 atoms per sample for environmental samples prepared using standard alpha spectrometry protocols. Recent measurements of 239 + 240 Pu and 241 Pu activities and 240 Pu/ 239 Pu isotope ratios in IAEA reference materials agree well with IAEA reference values and with alpha spectrometry and recently published inductively coupled plasma–mass spectrometry (ICP–MS) results. Ongoing upgrades of the AMS spectrometer are expected to reduce backgrounds below 1×10 6 atoms per sample while allowing simplifications of the sample preparation chemistry. These simplifications will lead to lower per-sample costs, higher throughput, faster turn around and, ultimately, to larger and more robust data sets.

The United States 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. The uptake of {sup 137}Cs by plants is enhanced because of the absence of mineral binding sites and the low concentration of potassium in the coral soil. {sup 137}Cs is bound to the organic fraction of the soil, whereas {sup 90}Sr, {sup 239+240}Pu and {sup 241}Am are primarily bound to soil particles. Assessment of plant uptake for {sup 137}Cs and {sup 90}Sr into locally grown food crops was a major contributing factor in (1) reliably predicting the radiological dose for returning residents, and (2) developing a strategy to limit the availability and uptake of {sup 137}Cs into locally g

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.

Over the past decade there has been growing concern over dumping of radioactive waste in the East Sea (Sea of Japan) proper and adjacent coastal waters. Here we show that the evolution of activity concentrations of 137Cs and 239+240Pu in the East Sea, and existing levels of radioactive contamination in waters, sediments and biota from Peter the Great Bay (Russia) can be largely attributed to global fallout deposition. The former sequence of data includes results from the AWARES cruise (Active Watch of Artificial Radionuclides in the East Sea) conducted between 26 October and 1 November 1993 about ten days after 14 GBq of liquid radioactive waste was dumped into the East Sea. The activity concentration of 137Cs and 239+240Pu in surface waters ranged between 2.7–3.5 Bq m−3 and 3.5–20.8 mBq m−3, respectively, and were not different to levels observed during August 1993 prior to the Russian dumping operation in October. Isotopic ratios also indicate the absence of any significant anthropogenic radioactive contamination in the region other than from global fallout deposition.

The International Atomic Energy Agency (IAEA) carried out an international project. 'The Study of the Radiological Situation at the Atolls of Mururoa and Fangataufa' with the aim of assessing the present and future radiological situation at the atolls and making recommendations for either monitoring or remedial actions if they are deemed necessary. The paper concentrates on marine radioactivity aspects and gives an estimation of present radionuclide concentrations in water, sediment and biota of the Mururoa and Fangataufa lagoons and the surrounding ocean. The dominant radionuclide in both lagoons is Pu in sediments (the total inventory is approximately 30 TBq). A decline in radionuclide concentrations has been observed in recent years in lagoon water, with the exception of 3H and 90Sr, for which a contribution from underground sources is to be expected. Radionuclide concentrations in biota from the lagoons and the surrounding ocean are low and consistent with previous measurements. The observed radionuclide concentrations in both lagoons imply that no radiological risk exists for hypothetical inhabitants of Mururoa and Fangataufa Atolls.

The Marshall Islands Program at the Lawrence Livermore National Laboratory has completed a series of radiological surveys at Bikini, Rongelap, Utrōk, and Enewetak Atolls in the Marshall Islands designed to take a representative sample of food supplies with emphasis on determining 137Cs activity concentrations in common food plants. Coconuts (Cocos nucifera L.) are the most common and abundant food plant, and provided a common sample type to characterize the level and variability of activity concentrations of 137Cs in plant foods collected from different islands and atolls. Other dominant food types included Pandanus (Pandanus spp.) and breadfruit (Actocarpus spp.). In general, the activity concentration of 137Cs in food plants was found to decrease significantly between the main residence islands on Bikini, Rongelap, Utrōk, and Enewetak Atolls. The mean activity concentration of 137Cs measured in drinking coconut meat and juice was 0.72 (95 % CI 0.68–0.77) and 0.34 (95 % CI 0.30–0.38) Bq g−1, respectively, on Bikini Island; 0.019 (95 % CI 0.017–0.021) and 0.027 (95 % CI 0.023–0.031) Bq g−1, respectively, on Rongelap Island; 0.010 (95 % CI 0.007–0.013) and 0.007 (95 % CI 0.004–0.009) Bq g−1, respectively, on Utrōk Island; and 0.002 (95 % CI 0.0013–0.0024) and 0.002 (95 % CI 0.001–0.0025) Bq g−1, respectively, on Enewetak Island. High levels of variability are reported across all islands. These results will be used to improve the accuracy and reliability of predictive dose assessments, help characterize levels of uncertainty and variability in activity concentrations of fallout radionuclides in plant foods, and allow atoll communities to make informed decisions about resettlement and possible options for cleanup and rehabilitation of islands and atolls.

Since the 1940, anthropogenic radionuclides have been intentionally and accidentally introduced into the environment through a number of activities including nuclear weapons development, production, and testing, and nuclear power generation. In the ensuing decades, a significant body of research has been conducted that not only addresses the fate and transport of the anthropogenic radionuclides in the marine environment but allows their application as tracers to better understand a variety of marine and oceanic processes. In many cases, the radionuclides are derived entirely from anthropogenic sources and the release histories are well constrained. These attributes, in conjunction with a range of different geochemical characteristics (e.g., half-life, particle affinity, etc.), make the anthropogenic radionuclides extremely useful tools. A number of long-lived and largely soluble radionuclides (e.g., 3H, 14C, 85Kr, 90Sr, 99Tc, 125Sb, 129I, 134Cs, 137Cs) have been utilized for tracking movement of water parcels in horizontal and vertical directions in the sea, whereas more particle-reactive radionuclides (e.g., 54Mn, 55Fe, 103Ru, 106Ru, Pu isotopes) have been utilized for tracking the movement of particulate matter in the marine environment. In some cases, pairs of parent-daughter nuclides (e.g., 3H-3He, 90Sr-90Y and 241Pu-241Am) have been used to provide temporal constraints on processes such as the dynamics of particles in the water column and sediment deposition at the seafloor. Often information gained from anthropogenic radionuclides provides unique/complementary information to that gained from naturally occurring radionuclides or stable constituents, and leads to improved insight into natural marine processes.

Trace metal fluxes have been determined for two lakes in south-eastern Australia. Lakes in the Melbourne metropolitan area and in a remote region of the Australian Alps were examined. Historic fluxes were calculated from the combination of trace metal concentrations and sedimentation rates. The trace metal concentrations of Pb, Cu and Zn were determined by conventional atomic absorption spectrophotometric methods, and the rates of sedimentation by 210 Pb dating. In the last 80 years the flux of Zn has increased 42-fold and Cu 30-fold in the Melbourne area. The flux of stable lead has increased 90-fold in the urban environment and 35-fold in the remote location. At the Melbourne site the average Pb flux over recent years has been 230 mg m −2 year −1 .

Radiation doses calculated for people resettling Bikini Island at Bikini Atoll, Enjebi Island at Enewetak Atoll, Rongelap Island at Rongelap Atoll, and Utrōk Island at Utrōk Atoll are presented. Residence is assumed to begin in 2010. In previous dose assessments it was shown that (137)Cs accounts for about 98% of the total dose for returning residents. About 85 to 90% (depending on the atoll) is via consumption of locally grown foods containing (137)Cs, and about 10 to 15% is due to external exposure from (137)Cs in the soil. These assessments were made using only the radiological half-life of (137)Cs (30.1 y). We have shown since that there is an environmental loss of (137)Cs from soil to groundwater that results in a more rapid loss of (137)Cs from the atoll ecosystem. The mean effective half-life of (137)Cs at the atolls is 8.5 y. Moreover, treatment of coconut trees with potassium (K) reduces (137)Cs concentration in drinking coconut meat at Bikini Atoll to about 5% of pretreatment concentrations. The magnitude of reduction is dependent on the concentration of (137)Cs in soil, and thereby in food crops, and is less for Enjebi and Rongelap Islands than for Bikini Island. Treatment of food crops and fruit trees with K and removal of the top 15 cm of soil around houses and community buildings prior to construction to reduce external exposure where people spend most of their time has been presented to the communities as a "Combined Option" remediation strategy. Doses presented here are calculated using the Combined Option, effective half-life of (137)Cs at the atolls, and a diet of both imported and local foods. The average natural background dose in the Marshall Islands, plus the anthropogenic nuclear test-related dose at Bikini, Enjebi, and Rongelap Islands, is less for each of the islands than the average background dose in the U.S. and Europe.

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.

The activity concentration of Cesium-137 ( 137 Cs) and naturally-occurring Polonium-210 ( 210 Po) were measured in the muscle tissue, kidney and liver of Pacific walrus ( Odobenus rosmarus divergens ) and bearded seal ( Erignathus barbatus ) collected by native hunters from the Bering Sea during May 1996. The mean 137 Cs concentrations in muscle, liver and kidney of Pacific walrus were 0.07, 0.09 and 0.07 Bq kg −1 ( n = 5, wet weight), respectively, and 0.17, 0.10, and 0.17 Bq kg −1 ( n = 2, wet weight), respectively, in bearded seal. In general, 137 Cs tissue concentrations are significantly lower than those previously reported for mammals from other regions. By comparison, 210 Po activity concentrations are more variable and appear to be higher level compared with mammal data from other regions. The mean 210 Po concentration in the muscle tissue, liver and kidney of Pacific walrus ( n = 5, wet weight) were 28.7, 189, and 174 Bq kg −1 , respectively. This compares with 210 Po concentration values ( n = 2, wet weight) of 27, 207 and 68 Bq kg −1 measured in the muscle tissue, liver and kidney, of bearded seal, respectively. Estimated concentration factors—as defined by the radionuclide concentration ratio between the target tissue to that in sea water—were two to three orders of magnitude higher for 210 Po that those of 137 Cs. We conclude from radiological dose estimates that ingestion of 137 Cs in foods derived from walrus and seal will pose no threat to human health. This work has important implications for assessment of risks of Alaskan coastal communities concerned about the dumping of nuclear waste in the Russia Arctic.

In response to sponsor interest in October 2005 we proposed two methods for enhancing the precision of {sup 233}U accelerator mass spectrometry (AMS) capabilities at the Lawrence Livermore National Laboratory (LLNL). In a previous report we evaluated the first method and demonstrated that by increasing sample loading by a factor of four coupled with performing four replicates of each sample, we could achieve measurement precision of {approx}1%. Recent modifications to our system have enabled us to test the second proposed method. By changing our setup to normalize {sup 233}U ions counted in a gas ionization chamber to {sup 238}U measured as a current in an off-axis Faraday cup we were able to attain 1% precision without the need for replicate analysis. This method could be further refined to achieve 0.5% precision in samples of interest.

Studies on the fate and transport of radioactive contaminates in the environment are often constrained by a lack of knowledge on the elemental distribution and general behavior of particulate bound radionuclides contained in hot particles. A number of hot particles were previously isolated from soil samples collected at former U.S. nuclear test sites in the Marshall Islands and characterized using non-destructive techniques [1]. The present investigation at HASYLAB is a part of larger research program at ITU regarding the characterization of environmental radioactive particles different locations and source-terms. Radioactive particles in the environment are formed under a number of different release scenarios and, as such, their physicochemical properties may provide a basis for identifying source-term specific contamination regimes. Consequently, studies on hot particles are not only important in terms of studying the elemental composition and geochemical behavior of hot particles but may also lead to advances in assessing the long-term impacts of radioactive contamination on the environment. Six particles isolated from soil samples collected at the Marshall Islands were studied. The element distribution in the particles was determined by confocal {micro}-XRF analysis using the ANKA FLUO beam line. The CRL (compound refractive lens) was used to focus the exciting beammore » and the polycapillary half lens to collimate the detector. The dimensions of confocal spot were measured by 'knife edge scanning' method with thin gold structure placed at Si wafer. The values of 3.1 x 1.4 x 18.4 {micro}m were achieved if defined as FWHMs of measured L?intensity profiles and when the19.1 keV exciting radiation was used. The collected XRF spectra were analyzed offline with AXIL [2] software to obtain net intensities of element characteristic lines.Further data processing and reconstruction of element distribution was done with the software 'R' [3] dedicated for statistical calculations. In figure 1 the distributions of Pu, Fe and Ti obtained for one of the studied hot particles are presented. The strongest signal was recorded for plutonium; the signals from iron and titanium are respectively 14 and 38 times less. It means that Pu is the most abundant of the observed elements. However, since the light elements are not detectable with the applied measurement conditions, it cannot be definitely stated if plutonium is the main element present in the sample. The isosurfaces are calculated at 20 % of maximum intensity for each element. Please note that the isosurfaces on the drawing are transparent. Changes in the spatial distribution of Pu, Fe, and Ti within the particle are shown in Fig. 2a, 2b, and 2c. Distinct elemental patterns are clearly visible at the higher concentration levels. The distributions of Cr, Cu, and Pb were also reconstructed but the results are not presented here. As it is shown in Fig. 1, the correlation between elements is good at low concentrations but the maxima of concentrations are not strongly correlated (see Fig. 2.). In general, the particle is inhomogeneous in terms of its elemental composition. Similar inhomogeneities were found for other particles with Pu identified as a major element in three of the six particles examined.« less

Under the auspices of the U.S. Department of Energy (USDOE), researchers from the Lawrence Livermore National Laboratory (LLNL) have recently implemented a series of initiatives to address long-term radiological surveillance needs at former nuclear test sites in the Republic of the Marshall Islands (RMI). The aim of this radiological surveillance monitoring program (RSMP) is to provide timely radiation protection for individuals in the Marshall Islands with respect to two of the most important internally deposited fallout radionuclides-cesium-137 ({sup 137}Cs) and long-lived isotopes 239 and 240 of plutonium ({sup 239+240}Pu) (Robison et al., 1997 and references therein). Therefore, whole-body counting for {sup 137}Cs and a sensitive bioassay for the presence of {sup 239+240}Pu excreted in urine were adopted as the two most applicable in vivo analytical methods to assess radiation doses for individuals in the RMI from internally deposited fallout radionuclides (see Hamilton et al., 2006a-c; Bell et al., 2002). Through 2005, the USDOE has established three permanent whole-body counting facilities in the Marshall Islands: the Enewetak Radiological Laboratory on Enewetak Atoll, the Utrok Whole-Body Counting Facility on Majuro Atoll, and the Rongelap Whole-Body Counting Facility on Rongelap Atoll. These whole-body counting facilities are operated and maintained by trained Marshallese technicians. Scientists from LLNL provide the technical support and training necessary for maintaining quality assurance for data acquisition and dose reporting. This technical basis document summarizes the methodologies used to calculate the annual total effective dose equivalent (TEDE; or dose for the calendar year of measurement) based on whole-body counting of internally deposited {sup 137}Cs and the measurement of {sup 239+240}Pu excreted in urine. Whole-body counting provides a direct measure of the total amount (or burden) of {sup 137}Cs present in the human body at the time of measurement. The amount of {sup 137}Cs detected is often reported in activity units of kilo-Becquerel (kBq), where 1 kBq equals 1000 Bq and 1 Bq = 1 nuclear transformation per second (t s{sup -1}). [However, in the United States the Curie (Ci) continues to be used as the unit of radioactivity; where 1 Ci = 3.7 x 10{sup 10} Bq.] The detection of {sup 239}Pu and {sup 240}Pu in bioassay (urine) samples indicates the presence of internally deposited (systemic) plutonium in the body. Urine samples that are collected in the Marshall Islands from volunteers participating in the RSMP are transported to LLNL, where measurements for {sup 239+240}Pu are performed using a state-of-the-art technology based on Accelerator Mass Spectrometry (AMS) (Hamilton et al., 2004, 2007; Brown et al., 2004). The urinary excretion of plutonium by RSMP volunteers is usually described in activity units, expressed as micro-Becquerel ({micro}Bq) of {sup 239+240}Pu (i.e., representing the sum of the {sup 239}Pu and {sup 240}Pu activity) excreted (lost) per day (d{sup -1}), where 1 {micro}Bq d{sup -1} = 10{sup -6} Bq d{sup -1} and 1 Bq = 1 t s{sup -1}. The systemic burden of plutonium is then estimated from biokinetic relationships as described by the International Commission on Radiological Protection (e.g., see ICRP, 1990). In general, nuclear transformations are accompanied by the emission of energy and/or particles in the form of gamma rays ({gamma}), beta particles ({beta}), and/or alpha particles ({alpha}). Tissues in the human body may adsorb these emissions, where there is a potential for any deposited energy to cause biological damage. The general term used to quantify the extent of any radiation exposure is referred to as the dose. The equivalent dose is defined by the average absorbed dose in an organ or tissue weighted by the average quality factor for the type and energy of the emission causing the dose. The effective dose equivalent (EDE; as applied to the whole body), is the sum of the average dose equivalent for each tissue weighted by each applicable tissue-specific weighing factor (which equates to the sensitivity of that tissue to damage by the equivalent radiation dose it receives). The SI unit of effective dose equivalent is the joule per kilogram (J kg{sup -1}), named the Sievert (Sv). The unit often used by federal and state agencies in the United States to describe EDE continues to be the more historical radiation equivalent man (rem); where 1 rem = 0.01 Sv.

This report contains individual radiological protection surveillance data developed during 2006 for adult members of a select group of families living on Utrok Atoll. These Group I volunteers all underwent a whole-body count to determine levels of internally deposited cesium-137 ({sup 137}Cs) and supplied a bioassay sample for analysis of plutonium isotopes. Measurement data were obtained and the results compared with an equivalent set of measurement data for {sup 137}Cs and plutonium isotopes from a second group of adult volunteers (Group II) who were long-term residents of Utrok Atoll. For the purposes of this comparison, Group II volunteers were considered representative of the general population on Utrok Atoll. The general aim of the study was to determine residual systemic burdens of fallout radionuclides in each volunteer group, develop data in response to addressing some specific concerns about the preferential uptake and potential health consequences of residual fallout radionuclides in Group I volunteers, and generally provide some perspective on the significance of radiation doses delivered to volunteers (and the general Utrok Atoll resident population) in terms of radiological protection standards and health risks. Based on dose estimates from measurements of internally deposited {sup 137}Cs and plutonium isotopes, the data and informationmore » developed in this report clearly show that neither volunteer group has acquired levels of internally deposited fallout radionuclides specific to nuclear weapons testing in the Marshall Islands that are likely to have any consequence on human health. Moreover, the dose estimates are well below radiological protection standards as prescribed by U.S. regulators and international agencies, and are very small when compared to doses from natural sources of radiation in the Marshall Islands and the threshold where radiation health effects could be either medically diagnosed in an individual or epidemiologically discerned in a group of people. In general, the results from the whole-body counting measurements of 137Cs are consistent with our knowledge that a key pathway for exposure to residual fallout contamination on Utrok Atoll is low-level chronic uptake of {sup 137}Cs from the consumption of locally grown produce (Robison et al., 1999). The error-weighted, average body burden of {sup 137}Cs measured in Group I and Group II volunteers was 0.31 kBq and 0.62 kBq, respectively. The associated average, annual committed effective dose equivalent (CEDE) delivered to Group I and Group II volunteers from {sup 137}Cs during the year of measurement was 2.1 and 4.0 mrem. For comparative purposes, the annual dose limit for members of the public as recommended by the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiological Protection (ICRP) is 100 mrem. Consequently, specific concerns about elevated levels of {sup 137}Cs uptake and higher risks from radiation exposure to Group I volunteers would be considered unfounded. Moreover, the urinary excretion of plutonium-239 ({sup 239}Pu) from Group I and Group II volunteers is statistically indistinguishable. In this case, the error-weighted, average urinary excretion of {sup 239}Pu from Group I volunteers of 0.10 {mu}Bq per 24-h void with a range between -0.01 and 0.23 {mu}Bq per 24-h void compares with an error-weighted average from Group II volunteers of 0.11 {mu}Bq per 24-h void with a range between -0.20 and 0.47 {mu}Bq per 24-h void. The range in urinary excretion of {sup 239}Pu from Utrok Atoll residents is very similar to that observed for other population groups in the Marshall Islands (Bogen et al., 2006; Hamilton et al., 2006a; 2006b; 2006c, 2007a; 2007b; 2007c) and is generally considered representative of worldwide background.« less

This report describes a standardized methodology used by researchers from the Center for Accelerator Mass Spectrometry (CAMS) (Energy and Environment Directorate) and the Environmental Radiochemistry Group (Chemistry and Materials Science Directorate) at the Lawrence Livermore National Laboratory (LLNL) for the full isotopic analysis of uranium from solution. The methodology has largely been developed for use in characterizing the uranium composition of selected nuclear materials but may also be applicable to environmental studies and assessments of public, military or occupational exposures to uranium using in-vitro bioassay monitoring techniques. Uranium isotope concentrations and isotopic ratios are measured using a combination of Multi Collector Inductively Coupled Plasma Mass Spectrometry (MC ICP-MS), Accelerator Mass Spectrometry (AMS) and Alpha Spectrometry.

The United States Department of Energy (U.S. DOE) has recently implemented a series of strategic initiatives to address long-term radiological surveillance needs at former U.S. nuclear test sites in the Marshall Islands. The plan is to engage local atoll communities in developing shared responsibilities for implementing radiation protection monitoring programs for resettled and resettling populations in the northern Marshall Islands. Using the pooled resources of the U.S. DOE and local atoll governments, individual radiological surveillance programs have been developed in whole body counting and plutonium urinalysis in order to accurately assess radiation doses resulting from the ingestion and uptake of fallout radionuclides contained in locally grown foods. Permanent whole body counting facilities have been established at three separate locations in the Marshall Islands including Rongelap Atoll (Figure 1). These facilities are operated and maintained by Marshallese technicians with scientists from the Lawrence Livermore National Laboratory (LLNL) providing on-going technical support services. Bioassay samples are collected under controlled conditions and analyzed for plutonium isotopes at the Center for Accelerator Mass Spectrometry at LLNL using state-of-the art measurement technologies. We also conduct an on-going environmental monitoring and characterization program at selected sites in the northern Marshall Islands. The aim of the environmentalmore » program is to determine the level and distribution of important fallout radionuclides in soil, water and local foods with a view towards providing more accurate and updated dose assessments, incorporating knowledge of the unique behaviors and exposure pathways of fallout radionuclides in coral atoll ecosystems. These scientific studies have also been essential in helping guide the development of remedial options used in support of island resettlement. Together, the individual and environmental radiological surveillance programs are helping meet the informational needs of the U.S. DOE and the Republic of the Marshall Islands. Our updated environmental assessments provide a strong scientific basis for predicting future change in exposure conditions especially in relation to changes in lifestyle, diet and/or land-use patterns. This information has important implications in addressing questions about existing (and future) radiological conditions on the islands, in determining as well as the implementation, cost and effectiveness of potential intervention options, and in general policy support considerations. Perhaps most importantly, the recently established individual radiological surveillance programs provide affected atoll communities with an unprecedented level of radiation protection monitoring where, for the first time, local resources are being made available to monitor resettled and resettling populations on a continuous basis. As a hard copy supplement to Marshall Islands Program website (http://eed.llnl.gov/mi/), this document provides an overview of the individual radiation protection monitoring program established for resettlement workers living on Rongelap Island along with a full disclosure of all verified measurement data (2002-2004). Readers are advised that an additional feature of the associated web site is a provision where users are able calculate and track doses delivered to volunteers (de-identified information only) participating the Marshall Islands Radiological Surveillance Program.« less

The US Department of Energy (DOE) has recently implemented a series of strategic initiatives to address long-term radiological surveillance needs at former US 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 US 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 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.

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.

Different stable elements, and some natural and man-made radionuclides, were used as tracers or associated in other ways with nuclear devices that were detonated at Bikini and Enewetak Atolls as part of the U.S. nuclear testing program from 1946 through 1958. The question has been raised whether any of these materials dispersed by the explosions could be of sufficient concentration in either the marine environment or on the coral islands to be of a health concern to people living, or planning to live, on the atolls. This report addresses that concern. An inventory of the materials involved during the test period was prepared and provided to us by the Office of Defense Programs (DP) of the United States Department of Energy (DOE). The materials that the DOE and the Republic of the Marshall Islands (RMI) ask to be evaluated are--sulfur, arsenic, yttrium, tantalum, gold, rhodium, indium, tungsten, thallium, thorium-230,232 ({sup 230,232}Th), uranium-233,238 ({sup 233,238}U), polonium-210 ({sup 210}Po), curium-232 ({sup 232}Cu), and americium-241 ({sup 241}Am). The stable elements were used primarily as tracers for determining neutron energy and flux, and for other diagnostic purposes in the larger yield, multistage devices. It is reasonable to assume that these materials would be distributed more » in a similar manner as the fission products subsequent to detonation. A large inventory of fission product and uranium data was available for assessment. Detailed calculations show only a very small fraction of the fission products produced during the entire test series remain at the test site atolls. Consequently, based on the information provided, we conclude that the concentration of these materials in the atoll environment pose no adverse health effects to humans. « less

In July 1993 and June 1995 drifting sediment traps were deployed near the Po outflow, in the coastal zone and in the Jabuka Pit in order to obtain quantitative information on the vertical flux of particulate material and export of organic carbon in the Northern and Middle Adriatic Sea. During these periods and in July 1994, the standing stock of carbon and nitrogen in the water column were also estimated. Carbon and nitrogen concentrations were higher in the north with a mean of 266 {micro}g C l{sup -1} in surface waters as compared to 92 {micro}g C l{sup -1} in Middle Adriatic; maximum concentrations were associated to the less-saline surface-subsurface waters in the north and to the chlorophyll a maximum in the Middle Adriatic. Organic carbon flux was roughly five times higher near the Po than in the more oligotrophic waters of the central region, with overall values (0.8 to 11.5 mg m{sup -2} d{sup -1}) being low compared to the open Northwestern Mediterranean. Comparison with primary production measurements yielded estimates of carbon export (f-ratio) of 4.7 and 3.4% in the Po and Pit stations, respectively, in 1993 and of 1.6 and 3.6% in the central part of the Adriaticmore » in 1995. These consistently low values suggest enhanced carbon recycling in the upper water column, even in regions characterized by different production and organic flux regimes. Zooplankton fecal pellets were important conveyors of organic carbon in this region; particularly those produced by fishes in the North and coastal sites.« less

Accelerator mass spectrometry (AMS) is an established technique for high throughput measurements of long-lived radioisotopes at very low abundance. At the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL), we are extending our AMS capabilities to the measurement of Plutonium and other actinides for application in a number of fields such as environmental fate and transport and bioassays of potentially exposed populations.

In the early 1970s after extensive characterisation of fallout the US Pacific Proving Grounds located at Enewetak Atoll began rehabilitation in preparation for the return of indigenous people who were relocated during the Cold War. Cleanup entailed removal and collection of ~545 GBq of contaminated topsoil, vegetation, and debris (concrete and metal) that was subsequently entombed within an unlined crater produced by an 18 kT surface test and capped with a concrete dome. The site is now known as the Runit Dome. Currently, the US Department of Energy conducts comprehensive radiological monitoring of people living on Enewetak Atoll, but characterisation of exposure risks posed by Runit Dome have been limited to catastrophic release scenarios and periodic atoll-wide environmental surveys. Furthermore, evidence indicates open hydraulic communication between waste and intruding ocean water, with migration pathways leading to local groundwater and circulating lagoon waters. Radionuclide migration is likely facilitated by colloids and dissolution/complexation reactions under low-pH anoxic conditions.

We have determined the level and distribution of gamma-emitting radionuclides, plutonium activity concentrations, and 240Pu/239Pu atom ratios in tissue samples of giant clam (Tridacna gigas and Hippopus hippopus), a top snail (Trochus nilaticas) and sea cucumber (Holothuria atra) collected from different locations around Enewetak Atoll. The plutonium isotopic measurements were performed using ultra-high sensitivity accelerator mass spectrometry (AMS). Elevated levels of plutonium were observed in the stomachs (includes the stomach lining) of Tridacna clam (0.62 to 2.98 Bq kg(-1), wet wt.), in the soft parts (edible portion) of top snails (0.25 to 1.7 Bq kg(-1)), wet wt.) and, to a lesser extent, in sea cucumber (0.015 to 0.22 Bq kg(-1), wet wt.) relative to muscle tissue concentrations in clam (0.006 to 0.021 Bq kg(-1), wet wt.) and in comparison with previous measurements of plutonium in fish. These data and information provide a basis for re-evaluating the relative significance of dietary intakes of plutonium from marine foods on Enewetak Atoll and, perhaps most importantly, demonstrate that discrete 240Pu239Pu isotope signatures might well provide a useful investigative tool to monitor source-term attribution and consequences on Enewetak Atoll. One potential application of immediate interest is to monitor and assess the health and ecological impacts of leakage of plutonium (as well as other radionuclides) from a low-level radioactive waste repository on Runit Island relative to background levels of fallout contamination in Enewetak Atoll lagoon.

A method is described for deposition of polonium isotopes on rotating silver discs. Rapid rotation during deposition gives a uniform deposit of high yield within an hour, and good α energy resolution simplifies the quantitative evaluation of the spectra.