Evaluation of measurements of 238Pu, 239Pu and 240Pu in urine at the microbecquerel level using thermal ionization mass spectrometry and alpha-spectrometry at Los Alamos National Laboratory: Results of a two year comparison test (LA-UR-06-8055)

The Intercomparison Studies Program (ISP) at the Oak Ridge National Laboratory (ORNL, Oak Ridge, TN, USA) provides natural-matrix urine quality-assurance/quality-control (QA/QC) samples to radiobioassay analysis laboratories. In 2003, a single laboratory (Los Alamos National Laboratory LANL, Los Alamos NM USA) requested a change in the test-samples provided previously by the ISP. The change was requested to evaluate measurement performance for analyses conducted using thermal-ionization mass spectrometry (TIMS). Radionuclides included ²³⁹Pu at two activity levels (75–150 μBq^·sample⁻¹ and 1200–1600 μBq^·sample⁻¹) and ²³⁸Pu (3700–7400 μBq^·sample⁻¹). In addition, ²⁴⁰Pu was added to the samples so that the ^239+240Pu specific activity was 3700–7400 μBq^·sample⁻¹. In this paper, the results of testing during the period May, 2003 through September, 2005 are presented and discussed.     

Using low resolution gamma detectors to detect and differentiate 239Pu and 235U fissions

When ²³⁹Pu and ²³⁵U undergo thermal neutron-induced fission, both produce significant numbers of beta-delayed gamma rays with energies in the several megaelectron volt range. Experiments using high energy-resolution germanium detectors have shown that it is possible to distinguish the fission of ²³⁹Pu from that of ²³⁵U. It is desirable to detect the presence of ²³⁵U or ²³⁹Pu using detectors that are less expensive and more rugged than high purity germanium detectors. To this end we demonstrate how differences in the energy spectrum and decay rates of the beta-delayed gamma rays can be used to identify ²³⁹Pu and ²³⁵U using low resolution plastic and liquid scintillator detectors. Experimental data are used to identify differences in the spectra and also to test the identification algorithms. Results to date are very promising.     

Transmutation of 239 Pu with spallation neutrons

Incineration studies of plutonium were carried out at the Synchrophasotron of the Joint Institute for Nuclear Research (JINR), Dubna, using proton beams with energies of 0.53 GeV and 1.0 GeV. Solid lead targets (8 cm in diameter and 20 cm long) were surrounded with 6 cm thick paraffin as neutron moderator and then irradiated. The transmutation of ²³⁹ Pu and the associated production of fission products ⁹¹ Sr, ⁹² Sr, ⁹⁷ Zr, ⁹⁹ Mo, ¹⁰³ Ru, ¹⁰⁵ Ru, ¹²⁹ Sb, ¹³² Te, ¹³³ I, ¹³⁵ I and ¹⁴³ Ce were studied in the present work. The plutonium samples (each 449 mg) were placed on the outer surface of moderator. For 1.0 GeV proton beam, the fission rate of ²³⁹ Pu is 0.0032 atoms per proton in one gram plutonium samples, for 0.53 GeV proton, this value is 0.0022. The experimental uncertainty is about 15%. The experiments are compared to two theoretical model calculations with moderate success, using the Dubna Cascade Model (CEM) and the LAHET code. The practical incineration rate of ²³⁹ Pu is very high. For example: if one uses 10 mA, 1 GeV proton beams under the same (fictive) experimental conditions, the incineration rate of ²³⁹ Pu via fission is 3 mg out of the 449 mg sample per day. For 0.53 GeV protons the corresponding rate is 2 mg per day.     

137Cs, 40K, 90Sr, 238, 239+240Pu, 241Am and 243+244Cm in forest litter and their transfer to some species of insects and plants in boreal forests: Three case studies

Results for ¹³⁷Cs, ⁴⁰K, ⁹⁰Sr, ^238,239+240Pu, ²⁴¹Am and ^243+244Cm measurements in plant, insects and forest litter samples collected at three sites in Poland are presented. New results are compared with some existing data for locations examined during previous studies. Insect samples were introduced now for the first time. Relatively high activities of ⁹⁰Sr were noticed for spruce bark beetle (Ips typographus) and those for ¹³⁷Cs, plutonium and ²⁴¹Am for forest dung beetle (Anoplotrupes stercorosus). Faster than caused by physical decay decrease of radiocesium activity was noticed for the majority of plant and litter samples. The results for ^239+240Pu for litter were similar to previous results, but the activities of ²³⁸Pu were smaller. The activity ratio between ²⁴¹Am and ^239+240Pu was found lower than expected for known proportions between global and Chernobyl fallout. Thus a kind of dynamic behavior of Pu and Am in the forest ecosystem is concluded. Transfer factors and aggregation coefficients were estimated and discussed for both plants and insects as well as between insects and the part of plants (or litter) they feed on. Many of them were never presented before.The authors are thankful to the Polish State Committee for Scientific Research for financial support of this investigation, Grant No. PG04 07520.     

A direct determination of 239Pu in femtomole range in aquatic solution by neutron activation

Summary A method is presented which facilitates the direct determination of ²³⁹Pu in aquatic solution by the (n,f) reaction with reactor neutrons and subsequent gamma spectrometry without chemical elaboration. Trace impurities of water constituent heavy metal elements are simultaneously determined through their (n, ) reactions. The sensitivity attained by this method is 1.6×10^–15 mol/l ²³⁹Pu by measuring the fission product pairs ¹³²Te/¹³²I or ¹⁴⁰Ba/¹⁴⁰La. The trace impurities determined in the range of 10^–810^–13 mol/l give an insight into the chemical behaviour of Pu in a given water. The natural uranium concentration plays a role to limit the Pu determination on the one hand and to help understanding the chemical behaviour of Pu on the other hand.

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Direkte Bestimmung von ²³⁹Pu in wäßriger Lösung im Femtomol-Bereich mit Hilfe der Neutronenaktivierung

Zusammenfassung Es wird eine Methode vorgestellt, die die direkte Bestimmung von ²³⁹Pu in wäßriger Lösung über die (n,f)-Reaktion mit Reaktorneutronen und mit anschließender gammaspektrometrischer Messung ohne chemische Aufbereitung ermöglicht. Spurenverunreinigungen der im Wasser enthaltenen Schwermetallelemente werden gleichzeitig über ihre (n, )-Reaktionen erfaßt. Durch die Messung der Spaltproduktpaare ¹³²Te/¹³²I oder ¹⁴⁰Ba/¹⁴⁰La wird bei dieser Methode eine Nachweisgrenze von 1,6×10^–15 mol/l ²³⁹Pu erreicht. Die bestimmten Spurenverunreinigungen im Bereich von 10^–8 bis 10^–13 mol/l geben einen Einblick in das chemische Verhalten von Pu in einem vorliegenden Wasser. Der natürliche Urangehalt spielt auf der einen Seite eine einschränkende Rolle bei der Pu-Bestimmung, trägt aber auf der anderen Seite zum Verständnis des chemischen Verhaltens von Pu bei.

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Dedicated to Prof. Dr. K. H. Lieser on the occasion of his 65th birthday     

The simultaneous determination of Th,Pu, Ra isotopes, 210Pb, 55Fe, 32Si and 14C in marine suspended phases

An efficient and systematic chemical procedure for the simultaneous measurement of Th, Pu, Ra isotopes, ²¹⁰Pb, ⁵⁵Fe, ³²Si and ¹⁴C in the same sample has been developed. This method has been applied successfully to the measurement of these isotopes in oceanic particulate samples collected from several tons of sea water. This procedure should find application in the analysis of geochemical samples.     

Sorption and desorption of 125I-, 137Cs+, 85Sr2+ and 152,154Eu3+ on disturbed soils under dynamic flow and static batch conditions

Sorption of radionuclides on homogenized soils (under 2.5 mm grain size) from synthetic groundwater of 8·10⁻³M ionic strength and pH 8.5 has been studied under dynamic (flow) and static (batch) conditions. The corresponding water-soluble compounds, as carriers in the 10⁻⁶ mol/dm³ concentration, were added into the SGW prior to the experiments. Soil samples were taken from several locations around the environment of the High Level Waste Storage Facility at Nuclear Research Institute Řež plc in 5–100 cm depth. The dynamic experiments were carried out in columns made of PP+PE injection syringes of 17.8 cm length and 2.1 cm in diameter. A multi-head peristaltic pump was used for pumping the water upward through the columns at a seepage velocity of about 0.06 cm/min in average. The radioactive nuclides were added into the water stream individually in a form of a short pulse in 0.1 cm³ of demineralized water. Dynamic desorption experiments were performed with the same experimental arrangement using a mixture of 10⁻²N H₂SO₄ and 10⁻²N HNO₃ in a volume ratio of 2: 1. Retardation, distribution and hydrodynamic dispersion coefficients during transport of radionuclides were determined by the evaluation of the integral form of a simple advection-dispersion equation, used for fitting experimental data and modeling the theoretical sorption breakthrough and desorption displacement curves. The static experiments were realized in 100 cm³ plastic bottles stirring 5 g of soil samples with SGW occasionally in a soil to SGW ratio of 1: 10 (m/V). Kinetic parameters including equilibrium sorption activity, activity transfer rate constants and sorption half-times were also determined. The results of dynamic experiments were compared with static sorption experiments.     

Development of a SIMS Method for Isotopic Measurements in Nuclear Forensic Applications

 Methodologies based on secondary ion mass spectrometry (SIMS) for isotopic measurements in nuclear forensic applications relevant to the age determination of Pu particles and isotopic composition of oxygen for geolocation assignment are described. For the age determination of Pu particles, a relative sensitivity factor (RSF) to correct for the different ionisation efficiencies of U and Pu, was obtained by analysing standard Pu materials with known ages. An RSF of 2.41±0.05 was obtained for PuO₂ from measurements on samples with different Pu/U ratios. In a sample of known origin, using this RSF value, the age calculated from the ²³⁸Pu/²³⁴U and ²⁴⁰Pu/²³⁶U ratios agreed well with the reported age of 2.3 years. For geolocation assignment, a new approach based on the measurement of differences in the natural abundance of ¹⁸O and ¹⁶O isotopes and their ratio was developed. The instrumental mass discrimination of the ¹⁸O/¹⁶O ratio was determined using three O-isotope samples of different chemical composition. The measured precision (the standard error of 100 cycles/analysis) obtained for the oxygen isotopic measurement on the samples was typically ±1.1‰.     

Discovery of the Heaviest Elements

The search for new superheavy elements (SHEs) is at present one of the most exciting adventures in nuclear physics. Thanks to enhanced experimental techniques, the synthesis of elements Z=113 to 118 in reactions using ⁴⁸Ca projectiles and targets made of isotopes of the elements neptunium to californium has been claimed. Discovery of the elements Z=114 (named flerovium) and Z=116 (named livermorium) has been accepted by the IUPAC. The others are waiting. The situation for element 113 is particular; here claims on discovery come from groups from RIKEN, Wako, Saitama, Japan and FLNR‐JINR, Dubna, Russia.     

Determination of 17O and 18O isotopic abundances in 238Pu materials by γ-ray spectrometry

A procedure has been developed for nondestructive determinations of ¹⁷O and ¹⁸O isotopic abundances in ²³⁸PuO₂ fuels produced for biomedical application. Close control of these isotopes is important because they increase the neutron emission rate caused by (α, n) reactions. γ-Rays accompanying these reactions are measured by a lithium-drifted germanium [Ge(Li)] detector and related to their respective isotopic abundances. Each determination has a detection limit approximating the lowest contents encountered in PuO₂ samples of 0.005% ¹⁷O and 0.001% ¹⁸O. The average deviations for each determination are estimated to be about ±25% at their detection levels, and less than ± 10% for abundances above 0.01%.     

Study of the isomeric ratios in photonuclear reactions of natural Selenium induced by bremsstrahlungs with end-point energies in the giant dipole resonance region

We have determined the isomeric ratios in ⁷⁴Se(γ, n)^73m,gSe and ⁸²Se(γ, n)^81m,gSe photonuclear reactions of natural Selenium induced by bremsstrahlungs with end-point energies in the giant dipole resonance region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8,192 channel analyzer and high-energy resolution (180 keV at gamma ray 1,332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

<Superscript>239, 240, 241</Superscript>Pu fingerprinting of plutonium in western US soils using ICPMS: solution and laser ablation measurements

Sector field inductively coupled plasma mass spectrometry (SF-ICPMS) has been used with analysis of solution samples and laser ablation (LA) of electrodeposited alpha sources to characterize plutonium activities and atom ratios prevalent in the western USA. A large set of surface soils and attic dusts were previously collected from many locations in the states of Nevada, Utah, Arizona, and Colorado; specific samples were analyzed herein to characterize the relative contributions of stratospheric fallout vs. Nevada Test Site (NTS) plutonium. This study illustrates two different ICPMS-based analytical strategies that are successful in fingerprinting Pu in environmental soils and dusts. Two specific datasets have been generated: (1) soils are leached with HNO₃-HCl, converted into electrodeposited alpha sources, counted by alpha spectrometry, then re-analyzed using laser ablation SF-ICPMS; (2) samples are completely dissolved by treatment with HNO₃-HF-H₃BO₃, Pu fractions are prepared by extraction chromatography, and analyzed by SF-ICPMS. Optimal laser ablation and ICPMS conditions were determined for the re-analysis of archived alpha spectrometry “planchette” sources. The best ablation results were obtained using a large spot size (200 μm), a defocused beam, full repetition rate (20 Hz) and scan rate (200 μm s⁻¹); LA-ICPMS data were collected with a rapid electrostatic sector scanning experiment. Less than 10% of the electroplated surface area is consumed in the LA-ICPMS analysis, which would allow for multiple re-analyses. Excellent agreement was found between ^239+240Pu activities determined by LA-ICPMS vs. activity results obtained by alpha spectrometry for the same samples ten years earlier. LA-ICPMS atom ratios for ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu range from 0.038–0.132 and 0.00034–0.00168, respectively, and plot along a two-component mixing line (²⁴¹Pu/²³⁹Pu = 0.013 [²⁴⁰Pu/²³⁹Pu] – 0.0001; r ² = 0.971) with NTS and global fallout end-members. A rapid total dissolution procedure, followed by extraction chromatography and SF-ICPMS solution Pu analysis, generates excellent agreement with certified ^239+240Pu activities for standard reference materials NIST 4350b, NIST 4353, NIST 4357, and IAEA 385. ^239+240Pu activities and atom ratios determined by total dissolution reveal isotopic information in agreement with the LA-ICPMS dataset regarding the ubiquitous mixing of NTS and stratospheric fallout Pu sources in the regional environment. For several specific samples, the total dissolution method reveals that Pu is incompletely recovered by simpler HNO₃-HCl leaching procedures, since some of the Pu originating from the NTS is contained in refractory siliceous particles.     

Comparison of alpha-spectrometry and alpha/gamma ratio method for the determination of americium in plutonium bearing fuel materials

Determination of americium is one of the requirements of chemical quality assurance of plutonium bearing fuel materials. Alpha-spectrometry is generally used for the determination of ²⁴¹Am in Pu bearing fuels since the efficiency of semiconductor detector used for alpha-spectrometry is independent of the alpha-particle energy in the 4 to 8 MeV range. However, this method has limitations for Pu samples containing extremely small or very large amounts of ²⁴¹Am. Thus an alternative methodology based on alpha/gamma (α/γ) activity ratio was developed and tested using different samples. The method is based on the determination of total γ-activity (of 60 keV peak) of an aliquot of the solution and the total α-activity present in the aliquot. The method is fast as it does not involve chemical separation of Pu and Am as required in the alpha-spectrometric method. Data obtained on synthetic and real life samples demonstrates the usefulness of the developed alpha/gamma ratio method for the determination of ²⁴¹Am in Pu bearing fuel samples.     

Measurement of the radioactivity of 238U, 226Ra, 210Pb, 228Th, 232Th, 228Ra, 137Cs and 40K in tea using gamma-spectrometry

The aim of the present work was to determine the concentration of radionuclides in all kinds of tea available at the local Egyptian market. Radioactivity of the nuclides ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Th, ²³²Th, ²²⁶Ra, ¹³⁷Cs and ⁴⁰K were measured in tea by direct γ-ray spectrometry using HPGe detector and their mean values were 16.0±5.3, 3.1±0.7, 34.3±3.4, 3.4±1.2, 3.0±0.6, 3.1±0.8, 0.9±0.2 and 623±25 Bq·kg⁻¹, respectively.     

On the estimation of the field constant of 35Cl nuclear quadrupole resonance frequency in the series of [R1R2R3AsCl]+M? compounds

The field constant of the NQR frequency of a chlorine atom (³⁵Cl) in a series of arsenic derivatives [R¹R²R³AsCl]⁺M⁻ was estimated from correlations. The field frequency is ∼41.5±3.5 Hz cm kV⁻¹, which is nearly twice as much as that in analogous phosphorus compounds. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1758–1760, August, 2005.     

Radioactivity of plutonium isotopes, <Superscript>137</Superscript>Cs and their ratio in sediment,seawater and biota from the east coast of Peninsular Malaysia

This study with sampling expeditions of marine sediment, seawater and biota were performed at 30 stations within Malaysian Exclusive Economic Zone (EEZ). A total of >400 samples were collected to determine the activity concentration of anthropogenic radionuclides (^239+240Pu, ¹³⁷Cs) and their activity ratio (^239+240Pu/¹³⁷Cs) in sediments, seawater and biota. The purpose of this study was to determine the concentration levels for these radionuclides and to evaluate any occurrence of radioactive contamination. Sediment cores were obtained using multicorer device, while water samples via co-precipitation techniques and biota was purchased from local fishermen. The activity concentrations of ^239+240Pu in sediment, seawater and biota were ranged 0.21–0.45 Bq/kg dry wt., 2.33–7.95 mBq/m³ and <0.008 Bq/kg fresh wt., respectively. Meanwhile, the values of ¹³⁷Cs were ranged <1.00–2.71 Bq/kg dry wt. in sediment, 3.40–5.89 Bq/m³ in seawater and <0.05–0.41 Bq/kg fresh wt. in biota, respectively. Activity ratios of ^239+240Pu to ¹³⁷Cs obtained seem to confirm that these artificial radioactivities were mainly due to global nuclear fallout.     

Effective doses due to intake of radiotoxic radionuclides 226Ra, 210Po and 210Pb through drinking water of coastal Karnataka

The concentrations of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb have been measured, by high efficiency 5″ × 5″ NaI(Tl) gamma ray spectrometer and chemical deposition method, in surface water samples from major rivers Kali, Sharavathi and Netravathi of coastal Karnataka. Measurements of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb in surface water from these rivers are important because the river water is main source of potable water in this region due to inadequate supply of treated water. The mean activity of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb in the surface water of the river Kali was found to be 5.13 mBq L⁻¹, 1.28 and 1.37 Bq L⁻¹, for Sharavathi River the mean activity was found to be 3.37 mBq L⁻¹, 1.30 and 1.44 Bq L⁻¹. In Netravathi River the mean activity of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb was found to be 3.30 mBq L⁻¹, 1.00 and 1.20 Bq L⁻¹. From the measured concentration of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb, the Effective dose to the population of the region was computed. The results of these systematic studies are presented and discussed in the paper.     

Study of the isomeric ratios in photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in ¹⁶⁵Ho(γ, n)^164m,gHo and ¹⁷⁵Lu(γ, n)^174m,gLu photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

238Pu, 239+240Pu, 241Am, 90Sr and 137Cs in mountain soil samples from the Tatra National Park (Poland)

Activity concentrations and inventory for ²³⁸Pu, ^239+240Pu, ²⁴¹Am, ⁹⁰Sr, and ¹³⁷Cs in soil from Tatra Mountains of Poland are presented. Soil samples were collected using 10 cm diameter cores down to 10 cm and sliced into 3 slices. Details of the applied procedure are described with the quality assurance program. The maximum activity concentrations found for various samples were: 1782±13 Bq/kg, 17.4±0.9 Bq/kg, 3.4±0.3 Bq/kg and 84±7 Bq/kg for ¹³⁷Cs, ^239+240Pu, ²⁴¹Am and ⁹⁰Sr, respectively. The maximum cumulated deposition of ^239+240Pu is 201±8 Bq/m². The origin of radionuclides is discussed, based mostly on the observed isotopic ratio of Pu. Significant correlations were found between ^239+240Pu, ²⁴¹Am and ¹³⁷Cs. The effective vertical migration rate seems to be in the order of: ⁹⁰Sr≫Pu>Am>Cs.     

First experiments on transmutation studies of129I and237Np using relativistic protons of 3.7 GeV

First experiments on the transmutation of long-lived¹²⁹I and²³⁷Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:¹²⁹I(n,)¹³⁰I and²³⁷Np(n,)²³⁸Np. The isotopes¹³⁰I (T _1/2-12.36 h) and²³⁸Np (T _1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (¹²⁹I(n,))=(10±2)b and (²³⁷Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna.