Showing papers in "Journal of Radioanalytical and Nuclear Chemistry in 2005"

A multi-detector continuous monitor for assessment of 222 Rn in the coastal ocean

Abstract: Radon-222 is a good natural tracer of groundwater discharge and other physical processes in the coastal ocean. Unfortunately, its usefulness is limited by the time consuming nature of collecting individual samples and traditional analysis schemes. We demonstrate here an automated multidetector system that can be used in a continuous survey basis to assess radon activities in coastal ocean waters. The system analyses 222 Rn from a constant stream of water delivered by a submersible pump to an air-water exchanger where radon in the water phase equilibrates with radon in a closed air loop. The air stream is fed to 3 commercial radon-in-air monitors connected in parallel to determine the activity of 222 Rn. By running the detectors out of phase, we are able to obtain as many as 6 readings per hour with a precision of approximately ±5–15% for typical coastal seawater concentrations.

Extraction of uranium(VI) from nitric acid medium by 1.1M tri-n-butylphosphate in ionic liquid diluent

Abstract: A systematic study on the extraction of U(VI) from nitric acid medium by tri-n-butylphosphate (TBP) dissolved in a non-traditional diluent namely 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) ionic liquid (IL) is reported. The results are compared with those obtained using TBP/n-dodecane (DD). The distribution ratio for the extraction of U(VI) from nitric acid by 1.1M TBP/bmimPF6 increases with increasing nitric acid concentration. The U(VI) distribution ratios are comparable in the nitric acid concentration range of 0.01M to 4M, to the ratios measured using 1.1M TBP/DD. In contrast to the extraction behavior of TBP/DD, the D values continued to increase with the increase in the concentration of nitric acid above 4.0M. The stoichiometry of uranyl solvate extracted by 1.1M TBP/IL is similar to that of TBP/DD system, wherein two molecules of TBP are associated with one molecule of uranyl nitrate in the organic phase. Ionic liquid alone also extracts uranium from nitric acid, albeit to a small extent. The exothermic enthalpy accompanying the extraction of U(VI) in TBP/bmimPF6 decreases with increasing nitric acid and with TBP concentrations.

Quantification of 234 Th recovery in small volume sea water samples by inductively coupled plasma-mass spectrometry

Abstract: Development of a small volume (2-4 liter) technique for measuring 234 Th in sea water has been instrumental in bringing to light small-scale structures in upper-ocean particle removal processes previously missed by standard 234 Th measurement techniques. Further development of this method to evaluate removal efficiencies of 234 Th via MnO2 precipitation quantified using ICP-MS are presented in this work. Advantages to this approach are precise knowledge of 234 Th recovery, while maintaining high sample throughput afforded by ICP-MS analyzes. The improved technique includes the acidification of 4-liter sea water samples and the addition of 230 Th as a yield monitor prior to MnO2 precipitation. Subsequent filtration and beta-counting of the high-energy daughter, 234mPa, was followed by a final background count after 6 half-lives (144 d) of decay. Filtered precipitates were dissolved with H2O2, and an internal standard of 229 Th was added. Samples were purified using anion-exchange chromatography to remove high levels of manganese, and recoveries were determined by measured ratios of 230 Th/229 Th by ICP-MS. Application of this procedure for 234 Th derived export in the recent Southern Ocean Iron Experiment showed average recoveries of 91%. Corrections for rare low recoveries (25-80%) noticeably change 234 Th profiles, thus impacting subsequent elemental flux calculations.

Natural radioactivity in phosphate rock, phosphogypsum and phosphate fertilizers in Brazil

Abstract: Phosphate deposits are generally characterized by enhanced radionuclide concentrations compared to natural levels. The mining and processing of this phosphate ore redistribute radionuclides throughout the environment and introduce them into phosphoric acid and phosphogypsum. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), NPK fertilizers and di-calcium phosphate (DCP). Contents of natural radionuclides from thorium and uranium series, 226 Ra, 210 Pb and 228 Ra, were measured in Brazilian igneous phosphate rock, phosphoric acid, phosphogypsum and phosphate fertilizer samples, using high-resolution gamma-spectrometry. Neutron activation analysis was used for the determination of U and Th in the same samples. The fertilizers samples which are derived directly from phosphoric acid, MAP and DAP, presented activity concentrations around the detection limits of the counting system for 226 Ra (<5.0 Bq . kg –1 ), for 228 Ra (<3.0 Bq . kg –1 ) and for 210 Pb (<19 Bq . kg –1 ). As for U and Th, the concentrations found in MAP and DAP are more significant, up to 374 and 250 Bq . kg –1 , respectively. SSP, TSP and NPK, which are obtained by mixing phosphoric acid with different amounts of phosphate rock and NH3, presented higher concentrations of radionuclides, up to 871 Bq . kg –1 for 226 Ra, 283 Bq . kg –1 for 228 Ra, 1255 Bq . kg –1 for 210 Pb, 413 Bq . kg –1 for U and 538 Bq . kg –1 for Th.

Application of Hypermet-PC in PGAA

Abstract: Hypermet-PC has been developed in the mid-nineties at the Institute of Isotopes and Surface Chemistry based on a successful FORTRAN code from the seventies. With additional calibration routines and other helping features it has proved to be a very useful tool in quantitative analysis performed either with NAA or with PGAA. The sophisticated built-in peak-shape function allows the fitting of asymmetric peaks from large-volume germanium detectors over a very wide energy range needed for PGAA. The experience collected when evaluating several thousands gamma-spectra acquired for routine analysis and spectroscopic research, is summarized in the paper.

Synthesis of 99mTc-pefloxacin: A new targeting agent for infectious foci

Abstract: This investigation focused on the labeling of pefloxacin, a fluoroquinolone antibacterial agent, with 99mTc to form 99mTc-pefloxacin complex. The labeling process was done by direct addition of pertechnetate in isotonic solution to Sn-pefloxacin solution. The labeling technique is effective, as a high labeling yield (98%) was obtained after 30-minute reaction time. Different factors were found that influenced this labeling reaction: 0.5 mg pefloxacin or more must be used to prevent the formation of colloids in the reaction medium. Fifty micrograms of stannous chloride dihydrate were found to be sufficient to reduce all pertechnetate with activity ranging from 37 to 3700 MBq without the detection of free pertechnetate or colloids in the reaction mixture. The pH of the reaction medium was found to play an important role in the labeling process. The labeling reaction proceeds well at neutral pH (pH 6) but at acidic pH value (pH 4 or below) the yield of 99mTc-pefloxacin complex decreased markedly to a labeling yield of 5%. The reaction mixture must be heated to 100 °C in an oil bath to enhance the formation of the 99mTc-pefloxacin complex. The biodistribution data show that 99mTc labeled pefloxacin was retained in infectious focus. The retention was specific since the abscess uptake of 99mTc-pefloxacin remained high as compared to the uptake of aseptic foci at 24-hour post injection. Also, the clearance of the tracer from other tissues is rapid on the contrary to its clearance from the septic focus. This supports the hypothesis that 99mTc-pefloxacin is retained at the infectious site because of its specific binding to the gyrase enzymes of bacterial cells.

Uranium adsorption characteristic and thermodynamic behavior of clinoptilolite zeolite

Abstract: Natural zeolite, clinoptilolite was tested for its ability to remove uranium from aqueous solutions. Influence parameters to the sorption process, such as initial uranium concentration, pH, contact time and temperature were investigated. Distribution coefficients of uranium on clinoptilolite were measured by batch technique. Experimental isotherms evaluated from the distribution coefficients were fit to Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models. Values of ΔH and ΔS were found as 0.93 and 56.09 J/mole, respectively. It was observed that the adsorption process is endothermic. Kinetics of uranium sorption was investigated at different time intervals at 30 °C. The reaction rate and diffusion constant were calculated.

Improved detector response characterization method in ISOCS and LabSOCS

Abstract: The In-Situ Object Calibration Software (ISOCS) and the Laboratory Sourceless Calibration Software (LabSOCS) developed and patented by Canberra Industries have found widespread use in the gamma spectrometry community. Using the ISOCS methodology, one can determine the full energy peak efficiencies of a Germanium detector in the 45 keV - 7 MeV energy range, for practically any source matrix and geometry. The underlying mathematical techniques used in ISOCS (and LabSOCS) have undergone significant improvements and enhancements since their first release in 1996. One of these improvements is a spatial response characterization technique that is capable of handling the large variations in efficiency that occurs within a small region. The technique has been in use in ISOCS and LabSOCS releases since 1999, and has significantly improved the overall quality of the close-in and off-axis response characterization for HPGe detectors, especially for Canberra's Broad Energy Germanium (BEGe) detectors. In this method, the detector response is characterized by creating a set of fine spatial efficiency grids at 15 energies in the 45 keV - 7 MeV range. The spatial grids are created in (r,θ) space about the detector, with the radius r varying from 0 to 500 meters, and the angle θ varying from 0 to π. The reference efficiencies for creating the spatial grids are determined from MCNP calculations using a validated detector model. Once the efficiency grids are created, the detector response can be determined at any arbitrary point within a sphere of 500-meter radius, and at any arbitrary energy within the specified range. Results are presented highlighting the improved performance achieved using the gridding methodology.

Radionuclides used for therapy and suggestion for new candidates

Abstract: Targeted radiotherapy has the potential to provide radiation doses from a wide range of radionuclides, some of them suitable for killing single cells while others are more suitable for killing tumor cell clusters of various sizes. A list of 64 radionuclides, including 20 new potential candidates for therapy (73Ga, 75Se, 87mSr, 97Ru, 103Ru, 113Sn, 113mIn, 117Sb, 123Sn, 131Cs, 139Ce, 141Ce, 149Eu, 167Tm, 170Tm, 173Tm, 195Au, 195mPt, 197Pt and 197Hg) were analyzed in terms of the suitability of their energies for killing tumor cells which grow as single, small, intermediate and large clusters. In addition, their possible production routes were studied.

Heavy metal inputs in Northern Patagonia lakes from short sediment core analysis

Abstract: Heavy metal profiles of short sediment cores sampled from lakes located in Nahuel Huapi National Park, Northern Patagonia, Argentina, were determined by INAA. Core dating was performed by measuring natural 210Pb and anthropogenic 137Cs, and by identification of tephra layers. No evidence was found for the input increase of the trace elements Sb, Ba, Cs, Zn, Co, Hf, Ni, Se, Sr, Ti, U, and V in the lake environment. High As concentrations (up to 250 μg . g-1) were found in relation with the diffusion processes of Mn and Fe oxides. Strong correlation was observed between the Br concentration and organic matter content, but no evidence was found for the relevant increase of Br inputs in recent years. Ag concentrations were found to be enriched in the upper core layers over the baseline values determined for deep layers ranging from 0.1 to 0.2 μg . g-1. Hg concentration profiles were also enriched in the upper core layers over the baseline (from less than 0.07 to 0.2 μg . g-1 for pre-industrial time, to 0.1 to 0.3 μg . g-1 for modern times) but in relation with the increased organic matter content of the sediment.

Some applications of neutron activation analysis

Abstract: Basic information on neutron activation analysis (NAA) and its application in environmental studies is presented. The fundamentals of the technique are shown while various methods of neutron activation analysis are briefly characterized in order to depict the most important information. A rich set of NAA applications for human and biological samples is given together with the short description of the results. The problems associated with the quality assurance and control are also pointed out and discussed. The information is addressed to researchers interested in the applications of neutron activation analysis or to those who are searching for a suitable alternative analytical technique for environmental studies on human and other biological samples, where other techniques are not the best choice.

The development of sequential separation methods for the analysis of actinides in sediments and biological materials using anion-exchange resins and extraction chromatography

Abstract: New, quantitative methods for the determination of actinides have been developed for application to marine environmental samples (e.g., sediment and fish). The procedures include aggressive dissolution, separation by anion-exchange resin, separation and purification by extraction chromatography (e.g., TRU, TEVA and UTEVA resins) with measurement of the radionuclides by semiconductor alpha-spectrometry (SAS). Anion-exchange has proved to be a strong tool to treat large volume samples, and extraction chromatography shows an excellent selectivity and reduction of the amounts of acids. The results of the analysis of uranium, thorium, plutonium and americium isotopes by this method in marine samples (IAEA-384, -385 and -414) provided excellent agreement with the recommended values with good chemical recoveries.

Analysis of high burnup spent nuclear fuel by ICP-MS

Abstract: We have used inductively coupled plasma mass spectrometry (ICP-MS) as the primary tool for determining concentrations of a suite of nuclides in samples excised from high-burnup spent nuclear fuel rods taken from light water nuclear reactors. The complete analysis included the determination of 95Mo, 99Tc, 101Ru, 103Rh, 109Ag, 137Cs, 143Nd, 145Nd,148Nd,147Sm, 149Sm, 150Sm, 151Sm, 152Sm, 151Eu, 153Eu, 155Eu, 155Gd, 237Np, 234U, 235U, 236U, 238U, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 242mAm, and 243Am. The isotopic composition of fissiogenic lanthanide elements was determined using high-performance liquid chromatography (HPLC) with ICP-MS detection. These analytical results allow the determination of fuel burn-up based on 148Nd, Pu, and U content, as well as provide input for storage and disposal criticality calculations. Results show that ICP-MS along with HPLC-ICP-MS are suitable of performing routine determinations of most of these nuclides, with an uncertainty of ±10% at the 95% confidence level.

The radioactivity of building materials

Abstract: Radiation exposure of the population can be increased appreciably by the use of building materials containing above-normal levels of naturally occurring radionuclides of terrestrial origin, as high as 1600 Bq. kg-1for 40K in granites, 700 Bq. kg-1for 226Ra in phosphogypsum and 360 Bq. kg-1for 232Th in granites. In a 25-year survey including more than two hundreds of different materials were investigated. Of the materials normally used in the building industry, i.e., red clay bricks, cement of Portland Types I and II, concretes, gravels and sand, contain regular levels of the primordial radionuclides. The adsorbed dose rate in indoor air, in general, does not exceed the dose criterion of 80 nGy. h-1or 0.3 mSv. y-1for the effective dose. Granites and phosphogypsum are the highly radioactive materials for which the absorbed dose rate in indoor air becomes up to five times higher than the dose criterion. It is recommended to avoid the use of those materials without radioactivity control.

How do we define the concepts specific activity, radioactive concentration, carrier, carrier-free and no-carrier-added?

Abstract: The fission of highly enriched uranium (HEU) by thermal neutrons creates dozens of isotopic products. The Isotope and Nuclear Chemistry Group participates in programs that involve analysis of “fresh' fission products by beta counting following radiochemical separations. This is a laborious and time-consuming process that can take several days to generate results. Gamma-spectroscopy can provide a more immediate path to isotopic activities, however, short-lived, high-yield isotopes can swamp a gamma-spectrum, making difficult the identification and quantification of isotopes on the wings and valley of the fission yield curve. The gamma-spectrum of a sample of newly produced fission products is dominated by the many emissions of a very few high-yield isotopes. Specifically, 132 Te ( T 1/2 = 3.2 d), its daughter, 132 I ( T 1/2 = 2.28 h), 140 Ba ( T 1/2 = 12.75 d), and its daughter 140 La ( T 1/2 = 1.68 d) emit at least 18 gamma-rays above 100 keV that are greater than 5p abundance. Additionally, the 1596 keV emission from 140 La imposes a Compton background that hinders the detection of isotopes that are neither subject to matrix dependent fractionation nor gaseous or volatile precursors. Some of these isotopes of interest are 111 Ag, 115 Cd, and the rare earths, 153 Sm, 154 Eu, 156 Eu, and 160 Tb. C-INC has performed an HEU irradiation and also “cold' carrier analyses by ICP-AES to determine methods for rapid and reliable separations that may be used to detect and quantify low-yield fission products by gamma-spectroscopy. Results and progress are presented.

Biosorption of toxic, heavy, no-carrier-added radionuclides by calcium alginate beads

Abstract: Studies on adsorption behavior of heavy radionuclides, present altogether in no-carrier-added state, e.g., 197-200Pb, 197-200Tl and 197Hg, have been carried out with calcium alginate beads. High lead (100%) and moderate thallium removal (~65%) was achieved in pH range 2-7. 100% mercury removal was also achieved at pH 2 and 4. Effort has been made to recover all three radionuclides adsorbed in the calcium alginate beads using various chemicals, such as HCl, thiourea, sodium acetate, sodium oxalate and sodium nitrite. It was found that 0.1M HCl and 0.1M thiourea could remove at pH 1 80-90% of adsorbed Pb. Tl recovery was possible by all chemicals mentioned above. Hg was also recovered by all chemicals except HCl.

Recent developments in the analysis of transuranics (Np, Pu, Am) in seawater

Abstract: A procedure is described to extend the current radiochemical method of seawater analysis for Pu and Am including Np. Short-lived 239Np tracer was prepared by separation from its 243Am parent. Irish Sea Water reference material (IAEA-381) containing known concentrations of 237Np, Pu isotopes and 241Am was used to test the procedure for small water volumes. Inductively-coupled plasma mass spectrometry (ICP-MS) was used in addition to alpha spectrometry for measurement of 237Np in the purified final Np fractions.

Production of therapeutic radioisotopes in the ORNL High Flux Isotope Reactor (HFIR) for applications in nuclear medicine, oncologyand interventional cardiology

Abstract: Greater availability of therapeutic radioisotopes is required to meet the demands for increasing clinical applications in nuclear medicine, oncology and interventional cardiology. Because of the need for very high specific activity products, methods other than direct neutron capture reactions (n,γ-elastic and n,n’-inelastic routes) are required to insure that the highest specific activity - and hopefully no carrier added (nca) - radioisotopes are available. Two major methods to obtain nca radioisotopes from reactors are through the use of radionuclide generator systems using reactor-produced parents and the formation of desired radioisotopes through beta-decay of reactor-produced species. In this paper we describe our recent development of new approaches to obtain nca 177Lu from the decay of reactor-produced 177Yb and free of the long-lived 177mLu (T1/2 = 160 d) radiocontaminant. We also describe preliminary results of our new “indirect” method for the production of 195mPt via decay of 195mIr, reactor-produced by neutron irradiation of highly enriched 193Ir.

Adsorption and thermodynamic behavior of uranium(VI) on Ulva sp .-Na bentonite composite adsorbent

Abstract: The algae-clay composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Ulva sp.) and clay (Na bentonite) were used to prepare composite adsorbent. The ability of the composite adsorbent to adsorp uranium(VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time. Parameters of desorption were also investigated to recover the adsorbed uranium. The adsorption patterns of uranium on the composite adsorbent followed the Freundlich and Dubinin-Radushkevich isotherms. The thermodynamic parameters such as the enthalpy ΔH, entropy ΔS and Gibbs free energy ΔG were calculated from the slope and intercept of lnKd vs. 1/T plots. The results suggested that the Ulva sp.-Na bentonite composite adsorbent is suitable as sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.

Preparation of [66Ga]bleomycin complex as a possible PET radiopharmaceutical

Abstract: Gallium-66 (T1/2 = 9.49 h) is an interesting radionuclide that has potential use for positron emission tomography (PET) imaging of biological processes in intermediate to slow target tissue uptake. 66Ga was produced in the NRCAM cyclotron as a result of 15 MeV proton bombardment of 66Zn with current intensity of 180 μA (yield 11.2 mCi/μAh). Bleomycin (BLM) was labeled with [66Ga]GaCl3

Neutron spectrum parameters in irradiation channels of the Nigeria Research Reactor-1 (NIRR-1) for the k0-NAA standardization

Abstract: The first nuclear research reactor in Nigeria has been commissioned for neutron activation analysis and limited radioisotope production. In order to extend its utilization to include the k0-standardization method, the following neutron spectrum parameters in inner and outer irradiation channels were determined by the “Cd-ratio for multi-monitor method”: the thermal-to-epithermal flux ratio, f, and the epithermal flux shape factor, α. Neutron spectrum parameters determined in the inner irradiation channel B2, are: α = -0.052±0.002 and f = 19.2±0.5. For the outer irradiation channel B4, the neutron spectrum parameters were found to be α = +0.029±0.003 and f = 48.3±3.3. The results are compared with the neutron spectrum parameters of other reactor facilities with similar core configuration such as the Slowpoke and Miniature Neutron Source Reactor facilities available in the literature.

Novel beta-gamma coincidence measurements using phoswich detectors

Abstract: We have developed an analysis pipeline for air filter gamma-ray spectra, utilizing the software packages UniSampo for peak analysis and Shaman for nuclide identification. In an automated usage mode, spectra that are received via e-mail are processed into a directory tree, analyzed with UniSampo and Shaman, and finally categorized on the basis of the analysis results. Alarms are generated if anything out of the ordinary is observed. Typical applications for an air filter analysis pipeline are national radioactivity surveillance networks and the global radionuclide monitoring network being implemented for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Our analysis pipeline system has been used by the Finnish national CTBT-authority, the Finnish National Data Center (FiNDC), since July 1999. Evaluation with a randomly selected set of 1518 air filter spectra showed that our pipeline system produces significantly better analysis results than that utilized by the CTBT Organization (CTBTO): our system found 4.2 more peaks per spectrum than the CTBTO system (9 p increase) and identified 5.6 more peaks per spectrum (14 p increase) on the average.

IAEA-MEL’s underground counting laboratory (CAVE) for the analysis of radionuclides in the environment at very low-levels

Abstract: An underground laboratory for low-level gamma- and beta-spectrometry has been constructed at IAEA-MEL, Monaco, for the analysis of environmental radionuclides. The laboratory is situated at a depth of 35 m water equivalent underground and equipped with 4, large volume HPGe detectors placed in a common lead shield with anti-cosmic plastic scintillator shielding. There is also an anti-Compton gamma-spectrometer, comprized of an HPGe detector and NaI(Tl) shielding, and finally, a Quantulus liquid scintillation spectrometer. The performance of the gammaspectrometers with different shielding settings/adjustments are discussed, as well as their possible applications in the analysis of natural and anthropogenic radionuclides in the marine environment.

Uranium Age Determination by Measuring the 230Th / 234U Ratio

Abstract: A radiochemical isotope dilution mass spectrometry method has been developed to determine the age of uranium materials. The amount of 230 Th activity, the first progeny of 234U, that had grown into a small uranium metal sample was used to determine the elapsed time since the material was last radiochemically purified. To preserve the sample, only a small amount of oxidized uranium was removed from the surface of the sample and dissolved. Aliquots of the dissolved sample were spiked with 233U tracer and radiochemically purified by anion-exchange chromatography. The 234U isotopic concentration was then determined by thermal ionization mass spectrometry (TIMS). Additional aliquots of the sample were spiked with 229 Th tracer, and the thorium was purified using two sequential anion-exchange chromatography separations. The isotopic concentrations of 230 Th and 232 Th were determined by TIMS. The lack of any 232 Th confirmed the assumption that all thorium was removed from the uranium sample at the time of purification. The 230 Th and 234U mass concentrations were converted to activities and the 230 Th/234U ratio for the sample was calculated. The experimental 230 Th/234U ratio showed the uranium in this sample was radiochemically purified in about 1945.

Sorption of Th(IV) ions onto TiO2: Effects of contact time, ionic strength, thorium concentration and phosphate

Abstract: The sorption of Th(IV) onto TiO2 was studied by the batch technique as a function of pH and ionic strength at moderate concentration (10-4-10-5 mol/l) and in the presence and absence of phosphate. It was found that the sorption rate of Th(IV) was relatively slow, the sorption percent was abruptly increased from pH 2 to 4, and the sorption was decreased with increasing ionic strength as a whole. In the concentration range of Th(IV) from trace concentration to 1.4 . 10-4 mol/l and in the absence of phosphate, the sorption isotherms were roughly fitted the Freundlich equation at different ionic strengths and approximately constant pH. These sorption characteristics of Th(IV) onto TiO2 were compared with those of uranyl on the same sorbent. In addition, the positive effect of phosphate on the sorption of Th(IV) onto TiO2 was demonstrated obviously and can be attributed to strong surface binding of phosphate, and the subsequent formation of ternary surface complexes of Th(IV). The difference between the sorption characteristics of Th(IV) ions and uranyl ions onto TiO2 is discussed.

Ultra-sensitive radionuclide spectrometry: Radiometrics and mass spectrometry synergy

Abstract: Recent developments in radiometrics and mass spectrometry techniques for ultra-sensitive analysis of radionuclides in the marine environment are reviewed. In the radiometrics sector the dominant development has been the utilization of large HPGe detectors in underground laboratories with anti-cosmic or anti-Compton shielding for the analysis of short and medium-lived radionuclides in the environment. In the mass spectrometry sector, applications of inductively coupled plasma mass spectrometry (ICP-MS) and accelerator mass spectrometry (AMS) for the analysis of long-lived radionuclides in the environment are the most important recent achievements. The recent developments do not only considerably decrease the detection limits for several radionuclides (up to several orders of magnitude), but they also enable to decrease sample volumes so that sampling, e.g., of the water column can be much easier and more effective. A comparison of radiometrics and mass spectrometry results for the analysis of radionuclides in the marine environment shows a reasonable agreement - within quoted uncertainties, for wide range of activities and different sample matrices analyzed.

Sorption of plutonium(VI) by hydroxyapatite

Abstract: The MARC-VI conference served as an excellent setting for a session organized to present and discuss the problems in nuclear science manpower and education. A panel discussion and contributed papers reflected the world-wide situation. This paper presents the major points of the panel discussion. As a result, a resolution on the current situation of nuclear chemistry and radiochemistry was drafted and endorsed by the conference attendees.

Determination of Pu isotopes in sediment cores in the Sea of Okhotsk and the NW Pacific by sector field ICP-MS

Abstract: Studies on the environmental behavior of plutonium in the marine environment require an analytical method with high sensitivity and capability to provide the isotopic composition of Pu in marine samples. In this work, as part of our on-going project on Pu environmental behavior in the Pacific Ocean, a sector field ICP-MS method combined with an off-line anion-exchange chromatography system was optimized for the determination of Pu and its atomic ratio of 240Pu/239Pu in sediment core samples. Using a conical concentric nebulizer and 150-second counting time, we were able to lower the detection limit of Pu down to 0.35 fg. The mass discrimination effect was evaluated using a mixed Pu isotope standard solution with certified a 240Pu/239Pu isotope ratio (NBS-947). The overall performance of the analytical method was validated by the determination of Pu and its isotope composition in an ocean sediment reference material (IAEA-368). Both the 239+240Pu activity and 240Pu/239Pu atomic ratio were found to be in good agreement with the certified and/or literature values. As an important application, we employed the analytical method to investigate the vertical profiles of 239+240Pu activity and 240Pu/239Pu atomic ratio in sediment cores in the Sea of Okhotsk and the NW Pacific. It was found that the Bikini close-in fallout Pu could be transported as far as the Sea of Okhotsk. The results provided evidence to support our hypothesis on the oceanic current transportation of Bikini close-in fallout Pu in the NW Pacific and its marginal seas.

Interrelationship of indoor radon concentrations, soil-gas flux, and meteorological parameters

Abstract: Passive electret-based radon flux monitors were deployed at 12-hour intervals for 1 year outside a single-family house, in order to access the variability and reliability of this method for estimation of indoor radon concentrations. Radon flux from the soil averaged 37 mBq/m 2 . s and showed small diurnal and seasonal fluctuations. Continuous basement-level radon measurements were collected at 5-minute intervals during the same time period, inside the house. The corresponding measurements allowed a direct comparison of the relationship of radon flux from the soil, using this method, and actual indoor radon concentrations at the house. Indoor radon levels showed strong diurnal and seasonal cycles, with the indoor radon concentrations during the year ranging from 50 to 1570 Bq/m 3 and averaging 360 Bq/m 3 . Meteorological measurements (barometric pressure, wind speed, temperature, and rainfall) collected at the site provided additional potentially correlative parameters to radon flux and indoor concentrations. While indoor radon levels at the house were not obviously affected by barometric pressure and wind speed, they were found to be strongly influenced by indoor and outdoor temperature differentials.

Production possibility of 61Cu using proton induced nuclear reactions on zinc for PET studies

Abstract: Excitation functions were measured by stacked-foil technique for the natZn(p,x)61Cu, 66Zn(p,x)61Cu, 68Zn(p,x)61Cu and natZn(p,x)60Cu nuclear processes up to 100 MeV. The experimental cross sections were compared with published data. On the base of these excitation functions, the cross sections of 64Zn(p,x)61Cu process were also deduced. Integral thick target yields were calculated for the 64Zn(p,x)61Cu and nat,64Zn(p,x)60Cu processes and irradiation parameters were elaborated for the 61Cu production via the 64Zn+p reactions for low and middle energy accelerators. According to our calculations the yield of 61Cu amounts to 1.02 . 1011 Bq . A-1 . s-1 (9.9 mCi .µ A-1 . h-1) from 19®10 MeV while it reaches 3.91 . 1011 Bq . A-1 . s-1 (38 mCi . µ A-1 . h-1) in the energy range of 67®60 MeV.