Compact Accelerator Mass Spectrometry Research Articles

Correction: Determination of ultra-low level of 239, 240Pu in grass/vegetable sample by compact accelerator mass spectrometry

Correction: Determination of ultra-low level of 239, 240Pu in grass/vegetable sample by compact accelerator mass spectrometry

Simultaneous Determination of Transuranium Radionuclides for Nuclear Forensics by Compact Accelerator Mass Spectrometry.

Accelerator mass spectrometry (AMS) is one of the most sensitive techniques used to measure the long-lived actinides. This is particularly of interest for determination of ultra-trace transuranium nuclides and their isotopic fingerprints for nuclear forensics. In this work, a new method was developed for simultaneous determination of transuranium nuclides (Np, Pu, Am, and Cm isotopes) by using 300 kV AMS after a sequential chemical separation of each group of actinides. 242Pu and 243Am were utilized as tracers for Np/Pu and Am/Cm yield monitoring. The results show that the chemical behaviors of Np and Pu on the TK200 column and those of Am and Cm on the DGA column were very consistent in 8-9 mol/L of HNO3 and 0.015-0.03 mol/L of NaNO2 media during the radiochemical separation. The AMS detection efficiencies for transuranium nuclides were also evaluated. The detection limits for all radionuclides are below femtogram level and even in attogram level for Pu and Cm isotopes. The established method has been successfully applied to accurately measure various transuranium nuclides in a single actinide radionuclide solution, demonstrating its feasibility for nuclear forensic investigation.

Determination of ultra-low level of 239, 240Pu in grass/vegetable sample by compact accelerator mass spectrometry

Determination of ultra-low level of 239, 240Pu in grass/vegetable sample by compact accelerator mass spectrometry

236U analyses with the ETH Zurich MILEA prototype system

Compact, low energy accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for the analysis of heavy and long lived radionuclides. In this study, we focus on the analytical capabilities of the compact AMS system MILEA, mainly for 236U analyses. First, the setup of the system for actinide analyses is presented and the special technical setup for 23xU/238U (x = 3, 6, 5) is discussed. Then, the background and sensitivity for 236U/238U are studied in detail, and finally results from the first routine runs are presented and discussed. Our results show that the ETH Zurich MILEA system is ideally suited for fast, reliable, high sensitivity, and almost background free analyses of 236U/238U in environmental samples allowing the analysis of larger batches of samples with reasonably small sample sizes or volumes.

Direct search for primordial 244Pu in Bayan Obo bastnaesite

The abundances of heavy elements produced in r-process nucleosynthesis in the early solar system need experimental verification. 244Pu could be the heaviest primordial nuclide produced before the formation of the Earth still being detectable today. As recent attempts failed to confirm the discovery of 244Pu signals at a concentration of 1.0 × 10−18 g/g in bastnaesite reported by Hoffman et al. in this study, the total primordial 244Pu in 450 g bastnaesite sample from Bayan Obo ore (China) was measured using ultra-sensitive compact accelerator mass spectrometry (AMS). As no 244Pu signal was detected, an upper limit for the 244Pu in our bastnaesite sample was estimated to be 2.1 × 10−20 g/g at 99% confidence level.

A new compact AMS facility at the Dongguk University

A compact accelerator mass spectrometry (AMS) system dedicated to measuring 14C was installed at the Dongguk University, Korea. Standards SRM 4990B (Ox-I), SRM 4990C (Ox-II), IAEA C-7, and IAEA C-8 were used to conduct the acceptance tests. Phthalic acid and IAEA C-1 were used to measure the background level. The results of the acceptance tests demonstrated the radiocarbon dating precision capabilities for 14C/12C and the background level. Moreover, a graphitization system for radiocarbon dating was installed. After installation, the AMS and graphitization systems were used to analyze archaeological, environmental, and petrochemical materials. The environmental samples were measured with AMS to study the relationship between CO2 emissions from fossil fuels and urban environmental variables. Analysis of leaves showed that urban population densities and CO2 emissions from fossil fuels were not significantly related. The cause of CO2 emissions in cities remains under study.

A New capability for 41Ca analysis using [formula omitted] at the Xi’an-AMS

The analysis of 41Ca can be quantified by measuring the ratio 41Ca/40Ca. At present, ratios of 41Ca/40Ca ≤ 10−11 can only be measured by accelerator mass spectrometry (AMS). The sensitivity is mainly limited by the interference of the isobar 41K. With compact AMS (≤1 MV), abundance sensitivities of 10−11 to 10−12 have been demonstrated, but this may necessitate the measurement of 39K to correct for the 41K background. With a 3 MV AMS, the dE/dx method can still be used to partially separate 41Ca from 41K. In this work, a new capability for 41Ca analysis has been tested at the Xi’an-AMS. Ca4+ was chosen to achieve a balanced performance between 41Ca/41K separation and transmission efficiency. A 41Ca/40Ca background level of near 10−13 was achieved without the need for 39K correction. This new analytical capability at our facility was then applied to 41Ca tracer samples from our studies on the “White Jade” land snail shells, in which 41Ca was used as a tracer for studying the absorption rate of calcium.

Determination of Atto- to Femtogram Levels of Americium and Curium Isotopes in Large-Volume Urine Samples by Compact Accelerator Mass Spectrometry

Ultralow level analysis of actinides in urine samples may be required for dose assessment in the event of internal exposures to these radionuclides at nuclear facilities and nuclear power plants. A new bioassay method for analysis of sub-femtogram levels of Am and Cm in large-volume urine samples was developed. Americium and curium were co-precipitated with hydrous titanium oxide from the urine matrix and purified by column chromatography separation. After target preparation using mixed titanium/iron oxides, the final sample was measured by compact accelerator mass spectrometry. Urine samples spiked with known quantities of Am and Cm isotopes in the range of attogram to femtogram levels were measured for method evaluation. The results are in good agreement with the expected values, demonstrating the feasibility of compact accelerator mass spectrometry (AMS) for the determination of minor actinides at the levels of attogram/liter in urine samples to meet stringent sensitivity requirements for internal dosimetry assessment.

Status of 236U analyses at ETH Zurich and the distribution of 236U and 129I in the North Sea in 2009

Compact, low energy accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for the analysis of heavy and long lived radionuclides. In this study, we will first focus on the analytical capabilities of the compact AMS system TANDY, mainly for 236U analyses, and then present a new dual tracer approach, that combines 129I and 236U. The measured 129I/236U ratios of samples collected in the North Sea in 2009 are in reasonable agreement with the expectations from documented or estimated releases from the two major nuclear reprocessing plants located at Sellafield (GB) and La Hague (F), suggesting that the 129I/236U ratio can be used as a water mass tag in the North Atlantic region. However, our results indicate that, in contrast to 129I, additional contributions of bomb produced 236U cannot be neglected in the North Sea region. This complicates the simple and straight forward use of the 129I/236U ratio as a quantitative tool for the calculation of transport times of North Sea water in the Arctic Ocean.

Low energy AMS of americium and curium

Accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for actinide analyses. While analyses of U and Pu isotopes have already become routine at the ETH Zurich 0.5MV AMS system “Tandy”, there is an increasing demand for highly sensitive analyses of the higher actinides such as Am and Cm for bioassay applications and beyond. In order to extend the actinide capabilities of the compact ETH Zurich AMS system and to develop new, more sensitive bioassay routines, a pilot study was carried out. The aim was to investigate and document the performance and the potential background of Am and Cm analyses with low energy AMS. Our results show that 241Am and Cm isotopes can be determined relative to a 243Am tracer if samples and AMS standards are prepared identically with regard to the matrix elements, in which the sample is dispersed. In this first test, detection limits for Cm and Am isotopes are all in the sub-femtogram range and even below 100ag for Cm isotopes. In a systematic background study in the mass range of the Cm isotopes, two formerly unknown metastable triply charged Th molecules were found on amu(244) and amu(248). The presence of such a background is not a principal problem for AMS if the stripper pressure is increased accordingly. Based on our first results, we conclude that ultra-trace analyses of Am and Cm isotopes for bioassay are very well possible with low energy AMS.

10Be and 26Al low-energy AMS using He-stripping and background suppression via an absorber

The transmission of the ion beam through a tandem accelerator is a critical parameter for efficient detection of long-lived radionuclides by sensitive accelerator mass spectrometry (AMS). With beam energies at the accelerator terminal of less than 600keV, high transmissions are obtained using He as stripper gas. Here, we discuss Be, B, and Al transmissions in view of their application in the AMS determination of the long-lived radioisotopes 10Be and 26Al with compact facilities. The charge state 2+ of Al and Be shows a high yield, but in both cases an intense background from other nuclides has to be handled. The applicability of a combination of an absorber cell with a gas ionization chamber was tested for suppression of the main background for 10Be2+ (10B2+) and 26Al2+ (13C1+). Energy loss simulations of the involved nuclides confirm the performance observed in the experiments. The findings concerning He stripping and detection methods at low energies may allow the construction of very compact AMS setups for light isotopes.

Isotope-selective laser photodetachment for 129I accelerator mass spectrometry

A pulsed injection-locked Ti:Sapphire laser and a negative ion laser ablation source are developed for compact accelerator mass spectrometry assisted by isotope-selective laser photodetachment. An output of about 60 mW at a repetition rate of 1 kHz is available using intracavity second-harmonic generation with a bandwidth of 20 MHz. A negative iodine ion pulse with a width of 100 ns is obtained by laser ablation of a NH4I sample. The negative ion source and the injection-locked Ti:Sapphire laser are suitable for trace analysis of 129I.

Present Status of YU-AMS System

A new compact accelerator mass spectrometry (AMS) system has been installed in the Kaminoyama Research Institute at Yamagata University (YU). The AMS system is based on a 0.5MV Pelletron accelerator developed by the National Electrostatics Corporation. An automated acid-alkali-acid (AAA) treatment system and an automated graphitization line were also installed in the same facility for sample preparation. Performance tests of the YU-AMS system were carried out by measuring the C-series standard samples (C1–C8) and HOxII provided by IAEA and NIST, respectively. We evaluated the YU-AMS system by comparing the radiocarbon ages of Japanese tree rings with dendrochronologically determined calendar ages with calibration data. We also carried out some performance tests using a control serum and a 14C-labeled drug (oxaliplatin).

Ultra-trace determination of plutonium in urine samples using a compact accelerator mass spectrometry system operating at 300 kV

Accelerator mass spectrometry (AMS) is a very sensitive and robust technique for analysis of long-lived radionuclides. Employment of the AMS technique can reduce the demands on sample preparation chemistry, due to its high rejection of interferences and low susceptibility to sample matrix. This is particularly of interest for ultra-trace determination of 239Pu in bioassay and environmental samples, as other mass spectrometric methods such as inductively coupled plasma mass spectrometry (ICP-MS) can suffer from isobaric mass interferences by the presence of uranium in the sample. A rapid sample preparation method for analysis of Pu at femtogram levels in large volume urine samples is described. Using the compact ETH AMS Tandy facility operating at ∼300 kV, the method was validated by analysing urine samples spiked with known amounts of 239/240/241Pu ranging from 1 to 30 fg. The detection limits for the method were estimated to be 0.38 fg for 239Pu, 0.40 fg for 240Pu and 0.08 fg for 241Pu in 1400 mL of urine.

A decade of AMS at the University of Georgia

In a span of 10 years, the University of Georgia’s Center for Applied Isotope Studies (CAIS) has transformed itself from principally a liquid scintillation counting (LSC) laboratory to one conducting thousands of accelerator mass spectrometry (AMS) and stable isotope ratio analysis (SIRA) annually. After receiving the first of the NEC compact AMS units in the United States, the CAIS began to meet the demand for 14C analysis outside the normal realm of most radiocarbon dating laboratories. With industry’s support, isotope research continued on an already developing natural products program to authenticate materials origin and process of formation. The CAIS’s AMS allowed for the detection of synthetic materials in milligram quantities rather than gram quantities required by LSC and allowed new compound specific SIRA techniques to be directed toward compound specific 14C measurement. By 2005 the CAIS was one of only a few laboratories accredited to determine bio-base content in industrial fuels and products by both AMS and LSC following ASTM D6866-10 [1].Since 2001, when our first sample was analyzed by AMS method, both radiocarbon and natural products sample numbers have increased steadily. The advantages of AMS analysis in overall efficiency, cost savings, accuracy, and precision, are detailed here in a review of analytical precision for radiocarbon and natural products analyzed over 10 years of AMS operation. Comparisons are made between natural products and bio-based materials analyzed by both AMS and LSC. Although high precision is not required to authenticate natural products, for the purpose of product comparison with regard to degree of naturalness accurate and precise 14C measurement is shown to be achievable by both methods.

Progress with a gas-accepting ion source for Accelerator Mass Spectrometry

The National Ocean Sciences AMS (NOSAMS) facility at Woods Hole Oceanographic Institution has developed a novel, gas-accepting microwave-plasma ion-source. The source is a key component of a compact Accelerator Mass Spectrometry (AMS) system built for the analysis of 14C in a continuously flowing gas stream. The gas source produces carbon currents from a stream of CO 2 with currents typical of a traditional graphite source. Details of the gas source, including ion current achieved, optimal flow rate, efficiency, and memory are presented. Additionally, data obtained from coupling a gas chromatograph to the source shown. Details about ion optics are presented separately [1].

The dissociation of 13CH and 12CH 2 molecules in He and N 2 at beam energies of 80–250 keV and possible implications for radiocarbon mass spectrometry

Isotopic ratios of 14C at natural levels can be efficiently measured with accelerator mass spectrometry (AMS). In compact AMS systems, 13CH and 12CH 2 molecular interferences are destroyed in collisions with the stripper gas, a process which can be described by dissociation cross sections. These dissociation cross sections determine the gas areal density required for sufficient attenuation of the interfering molecular beams, and are therefore key parameters in the effort to further reduce the terminal voltage and thus the size of the AMS system. We measured the dissociation cross sections of 13CH and 12CH 2 in N 2 and He in the energy range of 80–250 keV. In N 2, cross sections were constant for energies above 100 keV with average values per molecule of (8.1 ± 0.4) × 10 −16 cm 2 for 13CH and (9.5 ± 0.5) × 10 −16 cm 2 for 12CH 2. In He, cross sections were constant over the full measured range of 80–150 keV with average values of (4.2 ± 0.3) × 10 − 16 cm 2 and (4.8 ± 0.4) × 10 −16 cm 2, respectively. A considerable reduction of the terminal voltage from the currently used 200 kV while using N 2 for 13CH and 12CH 2 molecule dissociation is not possible: the required N 2 areal densities of ∼1.4 μg/cm 2, consequential angular straggling and a decreasing 1+ charge state fraction would reduce the ion beam transmission too much. This is not the case for He: sufficient molecule dissociation can be obtained with gas densities of ∼0.4 μg/cm 2, for which angular straggling is relatively small. In addition, the 1+ charge state fraction still increases at lower stripping energies. Thus, the usage of He for stripping and molecule dissociation might allow the development of even smaller 14C-AMS systems than available today.

Are Compact AMS Facilities a Competitive Alternative to Larger Tandem Accelerators?

In the last decade, small and compact accelerator mass spectrometry (AMS) systems became available operating at terminal voltages of 1 MV and below. This new category of instruments has become competitive for radiocarbon detection to larger tandem accelerators and many of these instruments are successfully used for 14C dating or biomedical applications. The AMS group at ETH Zurich has demonstrated that small instruments can be built, which allow measurements also of other radionuclides such as 10Be, 26Al, 129I, and the actinides. 41Ca measurements can be performed with sufficient sensitivity for biomedical applications. A summary of recent developments made at the 500kV Pelletron in Zurich is given and its performance is compared with that of a commercial compact instrument from the company High Voltage Engineering Europe (HVEE) in Amersfoort, the Netherlands, operating at 1MV at CNA in Seville, Spain, as well as with that of larger AMS facilities. It turns out that the ion optics, stripper design, and the detection system are critical for the performance.

A highly sensitive method for the reassessment and quantification of 239Pu in urine samples based on a 1 MV accelerator mass spectrometry system

A new and highly sensitive method for the determination of 239Pu in human urine has been developed permitting the reassessment of planchets initially prepared for alpha spectrometry (AS) analysis in the context of internal dosimetry. A set of urine samples (volume: 500 mL) was spiked with known quantities of 239Pu, ranging from 2 to 120 fg (4.6 μBq–0.3 mBq), employing 14 pg (2.05 mBq) of 242Pu as internal standard. The Pu was purified by ion-chromatography using BioRad AG1X2 anion-exchange resins (Bio-Rad Laboratories Inc.). The chemical yield was determined by alpha-spectrometry, being about 80%. Afterwards, the planchets so obtained were leached with diluted HNO3 and the dissolved plutonium was determined by Accelerator Mass Spectrometry (AMS) at the Centro Nacional de Aceleradores (CNA) in Seville, Spain. The minimum detectable activity (MDA) for the AMS measurements was determined through the study of a set of procedural blanks, giving figures of about 0.44 fg (∼1 μBq) per sample. This contrasts with the MDA obtained by AS for the same set of samples, of about 50 fg (∼0.1 mBq). The results now presented helps to demonstrate that the routine measurement of 239Pu at ultra trace levels in human urine samples is possible with the new-generation of compact AMS systems, offering a highly sensitive method for the reassessing of planchets prepared for bioassay purposes.

Measurement of 239Pu in urine samples at ultra-trace levels using a 1MV compact AMS system

Abstract Routine bioassay monitoring of Pu intake in exposed workers of research and nuclear industry is usually performed by alpha spectrometry. This technique involves large sample volumes of urine and time-consuming preparative and counting protocols. Compact accelerator mass spectrometry (AMS) facilities make feasible the determination of ultra low-level Pu activity concentrations and Pu isotopic ratios in biological samples (blood, urine and feces), being a rapid and cost-effective measurement technique. The plutonium results in urine samples presented here have been obtained on the 1 MV compact AMS system sited at the Centro Nacional de Aceleradores (CNA), in Seville, Spain. In this work, a different methodological approach has been developed alternative to the “classical” preparation of urine samples for alpha spectrometry. The procedure avoids the Pu precipitation step, and involves acid sample evaporation and acid digestion in a microwave oven. Finally, purification of plutonium was achieved by using chromatography columns filled up with BioRad AG1X2 anion exchange resin (Bio-Rad Laboratories Inc.). The total time needed for analysis is about 10 h, unlike the “classical” methods based on alpha spectrometry which need about 1 week. At present, it has been demonstrated that this method allows quantifying 239Pu activity concentrations in urine of, at least, 30 μBq (13 fg 239Pu). We can conclude that the procedure would be suitable to perform in vitro routine bioassay measurements. Moreover, the innovative application of AMS opens new and interesting analytical alternatives in this field.