[en] Plutonium-239 (²³⁹Pu) and plutonium-239+240 (^239+240Pu) activities concentrations and ²⁴⁰Pu/²³⁹Pu atom ratios are reported for a series of chemically purified soil extracts received from the Carlsbad Environmental Monitoring and Research Center (CEMRC) in New Mexico. Samples were analyzed without further purification at the Lawrence Livermore National Laboratory (LLNL) using accelerator mass spectrometry (AMS). This report also includes a brief description of the AMS system and internal laboratory procedures used to ensure the quality and reliability of the measurement data

[en] 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 on the Alaskan peninsula. Plutonium isotope measurements were performed in replicate using Accelerator Mass Spectrometry (AMS). The average ²⁴⁰Pu/²³⁹Pu atom ratio observed in dried Fucus d. 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 (Cooper et al., 2000). In general, the characteristically high ²⁴⁰Pu/²³⁹Pu content of Fucus d. analyzed in this study appear to indicate the presence of a discernible basin-wide secondary source of plutonium entering the marine environment. Of interest to the study of plutonium source terms within the Pacific basin are reports of elevated ²⁴⁰Pu/²³⁹Pu atom ratios in fallout debris from high-yield atmospheric nuclear tests conducted in the Marshall Islands during the 1950s (Diamond et al., 1960), the wide range of ²⁴⁰Pu/²³⁹Pu atom ratio values (0.19 to 0.34) observed in sea water, sediments, coral and other environmental media from the North Pacific Ocean (Hirose et al., 1992; Buesseler, 1997) and updated estimates of the relative contributions of close-in and intermediate fallout deposition on oceanic inventories of radionuclidies, especially in the Northern Pacific Ocean (Hamilton, 2004)

[en] We report on the development of an accelerator mass spectrometry (AMS) system for the measurement of actinides at Lawrence Livermore National Laboratory. This AMS system is centered on a recently completed heavy isotope beam line that was designed particularly for high sensitivity, robust, high-throughput measurements of actinide concentrations and isotopic ratios. A fast isotope switching capability has been incorporated in the system, allowing flexibility in isotope selection and for the quasi-continuous normalization to a reference isotope spike. Initially, our utilization of the heavy isotope system has concentrated on the measurement of Pu isotopes. Under current operating conditions, background levels equivalent to ∼1 x 10⁵ atoms are observed during routine ²³⁹Pu and ²⁴⁰Pu measurements. Measurements of samples containing ∼10¹³²³⁸U atoms demonstrate that the system provides a ²³⁸U rejection factor during ²³⁹Pu measurements of ∼10⁷. Measurements of known materials, combined with results from an externally organized inter-comparison program, indicate that our ²³⁹Pu measurements are accurate and precise down to the (micro)Bq level (∼10⁶ atoms). Recently, we have investigated the performance of our heavy isotope AMS system in measurements of ²³⁷Np and ²³⁶U. Results of these investigations are discussed. The sensitivity shown by our Pu measurements, combined with the high throughput and interference rejection capabilities of our AMS system, demonstrate that AMS can provide a rapid and cost-effective measurement technique for actinides in a wide variety of studies

[en] The application of ultra-sensitive heavy isotope measurements continues to expand in a variety of fields relevant to the management of nuclear materials, including nuclear isotope forensics and radiobioassay. We have developed a heavy isotope accelerator mass spectrometry (AMS) system at Lawrence Livermore National Laboratory's (LLNL) Center for Accelerator Mass Spectrometry (CAMS). The system was designed particularly for the measurement of actinide concentrations and isotopic ratios, but also allows the measurement of other heavy isotopes such as ¹²⁹I. The system includes a fast isotope switching capability that allows flexibility in isotope selection and for the quasi-continuous normalization to a reference isotope spike. Current background levels for ²³⁹Pu and ²⁴⁰Pu are equivalent to <10⁶ atoms and measurements of known materials indicate that our ²³⁹Pu and ²⁴⁰Pu measurements are accurate and precise for samples containing from ∼10¹² atoms down to the Bq level (∼10⁶ atoms). Recent exploitation of the fast isotope switching capability has allowed the quasi-simultaneous measurement of several Pu isotopes in individual samples. Our AMS measurement capability has been extended to U isotopes, with particular emphasis on ²³⁶U. Our current ²³⁶U background level is equivalent to ∼10⁶ atoms and the linear measurement range is 5-6 orders of magnitude. We have also utilized our Heavy Isotope AMS system for the measurement of ¹²⁹I. Initial measurements of available low level samples show that background contributions for 1 mg I samples are below ¹²⁹I/¹²⁷I levels of ∼10^-14, and measurements of prepared standard samples demonstrates linear measurement response to ¹²⁹I/¹²⁷I levels greater than 10^-10. The AMS technique provides high rejection of interferences, including molecular interferences, and low susceptibility to matrix components, both of which are of particular relevance to the measurement of complex sample matrices. The attendant significant reductions of demands on sample preparation chemistry allow relatively simple, cost-effective procedures to be employed. When such sample preparation improvements are combined with the high sample throughput capabilities of our AMS system, the result is a rapid and cost-effective measurement technique for heavy isotopes in a wide range of studies

[en] We have developed refined statistical and modeling techniques to assess low-level uptake and urinary excretion of plutonium from different population group in the northern Marshall Islands. Urinary excretion rates of plutonium from the resident population on Enewetak Atoll and from resettlement workers living on Rongelap Atoll range from <1 to 8 (micro)Bq per day and are well below action levels established under the latest Department regulation 10 CFR 835 in the United States for in vitro bioassay monitoring of ²³⁹Pu. However, our statistical analyses show that urinary excretion of plutonium-239 (²³⁹Pu) from both cohort groups is significantly positively associated with volunteer age, especially for the resident population living on Enewetak Atoll. Urinary excretion of ²³⁹Pu from the Enewetak cohort was also found to be positively associated with estimates of cumulative exposure to worldwide fallout. Consequently, the age-related trends in urinary excretion of plutonium from Marshallese populations can be described by either a long-term component from residual systemic burdens acquired from previous exposures to worldwide fallout or a prompt (and eventual long-term) component acquired from low-level systemic intakes of plutonium associated with resettlement of the northern Marshall Islands, or some combination of both

[en] 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 study 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 (micro)Bq/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 (micro)Bq 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 (micro)Bq/ml. From the results of the two studies, it can be inferred that the best performance at the (micro)Bq 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