Showing papers in "Journal of Radioanalytical and Nuclear Chemistry in 2009"

Characterization of MX-80 bentonite and its sorption of radionickel in the presence of humic and fulvic acids

Abstract: MX-80 bentonite is considered as one of the best backfill materials for high-level radioactive nuclear waste Herein, the bentonite is characterized by using XRD and FTIR techniques Sorption of radionickel to MX-80 bentonite in the presence/absence of humic acid (HA) or fulvic acid (FA) as a function of pH is investigated The results indicate that the presence of HA or FA decreases the sorption of Ni2+ obviously The different experimental processes do not affect the sorption of nickel to FA/HA bound bentonite The sorption of Ni2+ on FA/HA-bound bentonite decreases with the increasing FA/HA content in the systems The mechanism of nickel sorption is also discussed in detail

Mössbauer spectroscopy with high velocity resolution: an increase of analytical possibilities in biomedical research

Abstract: Mossbauer spectroscopy is a useful technique for biomedical applications. To increase analytical possibilities and quality of its biomedical applications a new Mossbauer spectrometric system was developed. This system based on a highly stable, sensitive and precision spectrometer SM-2201 with high velocity resolution and a temperature variable liquid nitrogen cryostat with a moving absorber. The first results of Mossbauer spectroscopy with high velocity resolution demonstrated a decrease in the experimental error in the determination of 57Fe hyperfine parameters and, therefore, an increase of accuracy in analysis of small variations of the iron electronic structure, as well as more reliable fitting of complicated spectra.

Measurements of radioxenon in ground level air in South Korea following the claimed nuclear test in North Korea on October 9, 2006

Abstract: Following the claimed nuclear test in the Democratic People’s Republic of Korea (DPRK) on October 9, 2006, and a reported seismic event, a mobile system for sampling of atmospheric xenon was transported to the Republic of South Korea (ROK) in an attempt to detect possible emissions of radioxenon in the region from a presumed test. Five samples were collected in the ROK during October 11–14, 2006 near the ROK–DPRK border, and thereafter transported to the Swedish Defense Research Agency (FOI) in Stockholm, Sweden, for analysis. Following the initial measurements, an automatic radioxenon sampling and analysis system was installed at the same location in the ROK, and measurements on the ambient atmospheric radioxenon background in the region were performed during November 2006 to February 2007. The measured radioxenon concentrations strongly indicate that the explosion in October 9, 2006 was a nuclear test. The conclusion is further strengthened by atmospheric transport models. Radioactive xenon measurement was the only independent confirmation that the supposed test was in fact a nuclear explosion and not a conventional (chemical) explosive.

Uranium assay determination using Davies and Gray titration: an overview and implementation of GUM for uncertainty evaluation

Abstract: The International Organization for Standardization (ISO) Guide to the expression of Uncertainty in Measurement (GUM) was developed to meet the demand for a standardized way of evaluating and expressing uncertainties. The Davies and Gray (D&G) titrimetry method is routinely used in nuclear safeguards for uranium accountability measurement and a statement of the uncertainty that can reasonably be attributed to the measured assay value is therefore of importance. A mathematical model for an uncertainty evaluation of D&G measurements in compliance with ISO GUM is presented. This is illustrated by a numerical example and the utilization of the uncertainty budget is explored.

Solvent extraction of microamounts of strontium and barium into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of polyethylene glycol PEG 600

Abstract: Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of polyethylene glycol PEG 600 (L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, H2L2+, ML2+ and MHL3+ (M2+ = Sr2+, Ba2+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that in water-saturated nitrobenzene the stability constant of the BaL2+ cationic complex species is essentially higher than that of the complex SrL2+.

Natural radioactivity in bottled natural spring, mineral and therapeutic waters in Poland

Abstract: Activities of 238U, 234U, 228Ra, 226Ra, and 224Ra as well as total α- and β-activities of 23 bottled spring, mineral and therapeutic waters produced and distributed in southern and central Poland are presented. The activities vary from a few tenth to a few mBq·L−1 for uranium and to several hundred mBq·L−1 for radium isotopes. The activities of 40K were calculated from chemical analyses of potassium and checked for several mineral waters by gamma-spectrometer coupled with an HPGe detector. Positive correlation between water mineralization and activities of 40K, 226Ra, as well as total alpha- and total beta-activities were observed. The radiological annual doses were calculated for all investigated waters and for different human age groups assuming the consumption of 1 liter of water per day. The calculated committed effective dose rate from uranium and radium isotopes resulting from consumption of the investigated waters exceeds the recommended value of 0.1 mSv per year in seventeen cases for infants and in one case for adults.

Sorption of strontium on Slovak bentonites

Abstract: Sorption of Sr on five Slovak bentonites of deposits has been studied with the use of batch technique. In the experiments there have been used natural, chemically modified and irradiated samples, in three different kinds of grain size. The pH influence on sorption of strontium on bentonites, pH change after sorption and influence of competitive ions have been studied. Distribution ratios have been determined for bentonite–strontium solution system as a function of contact time, pH and sorbate concentration. The data have been interpreted in term of Langmuir isotherm. The uptake of Sr has been rapid and the sorption of strontium has increased by increasing pH. The percentage sorption has decreased with increasing metal concentrations. The pH value after sorption for the natrificated forms of bentonite starts already in the alkaline area and moves to the higher values. For the natural bentonites the values occur in the neutral or in the acidic area. Sorption of Sr has been suppressed by presence of competitive cations as follows: Ba2+ > Ca2+ > Mg2+ > NH4+ > K+ > Na+. By sorption on natrificated samples colloidal particles and pH value increase have been formed. The bentonite exposure as a result of interaction of γ-rays has led to expansion of the specific surface, increasing of the sorption capacity and to the change in the solubility of the clay materials.

Profile of selenium in soil and crops in seleniferous area of Punjab, India by neutron activation analysis

Abstract: In the Nawanshahr–Hoshiarpur region of Punjab, India, more than 1000 hectares of agricultural land is significantly affected by high levels of selenium (Se). Studies were carried out to examine Se levels in soil and crops such as wheat grains, wheat husk, rice, maize and mustard using neutron activation analysis. The Se concentrations in soil and crop products were found to be ranging from 2.7 to 6.5 mg kg−1 and 13 to 670 mg kg−1, respectively, indicating significantly high selenium in these crop products. Two reference materials were analysed for Se contents by INAA as controls.

Study on the retention of uranyl ions on modified clays with titanium oxide

Abstract: The experimental equilibrium adsorption data were tested for the Langmuir, Freundlich, Temkin and Redlich-Peterson equations. Results indicate the following order to fit the isotherms equations: Freundlich > Redlich-Peterson > Temkin > Langmuir. Influence parameters to the sorption process, such as initial concentration of uranium, contact time, solid/liquid ratio, were investigated using a batch mode technique. The results indicate that the adsorption of UO22+ ions from aqueous solution depends on the concentration of uranium in simulated wastewater, on contact time and on the ratio of sorbent/solution value. Some thermodynamic parameters (ΔHo, ΔSo and ΔGo) of the adsorption system were also determined. Thermodynamic values of ΔHo, ΔSo and ΔGo show spontaneous and endothermic nature of the sorption process of uranium ions from simulated wastewaters. The depletion of the uranium uptake at higher initial solution concentration (C>0.5 μg/mL) is probably attributed to the surface precipitation processes, which produce the blockage of micropores and disturb the ionic process evolution. The obtained results underline the possibility that Romanian modified clays can be used for the treatment of radioactive liquid waste containing UO22+ ions.

A new sorbent for uranium extraction: Polyethyleniminephenylphosphonamidic acid

Abstract: A new sorbent, polyethyleniminemethylenephosphonamidic acid (PEIPPA), was synthesized from commercially available polyethylenimine and P,P-dichlorophenylphosphine oxide. After characterization by (1H, 13C, 31P) NMR and FTIR, the new ion-exchange polymer has been investigated in liquid-solid extraction of uranium. The extraction strongly depends on the pH, initial concentration of uranium, extractant to analyte ratio (mol/mol), ionic strength of the liquid medium and their mutual interactions. Such interactions were investigated through factorial 33 experimental designs in order to achieve the best conditions of batch sorption procedure, obtaining the mutual interaction among variables and optimizing these variables. The recovery of U(VI) is almost quantitative.

Development of diode junction nuclear battery using 63Ni

Abstract: The diode junction nuclear battery is a long-lived, high-energy-density, but low electrical current power source with many specialized applications. In this type of battery, nuclear radiation is directly converted to electric power. A model is described and used to design the device configuration. Details of fabrication and testing of a planar geometry battery with 63Ni radiation source are described. The electron beam induced current (EBIC) measurement technique and CASINO Monte Carlo simulation code were employed to analyze the device performance. Finally, an improved design with 3-dimensional surface microstructures that will provide improved performance is presented.

Adsorption of cesium on domestic bentonites

Abstract: Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for spent nuclear fuel and high-level nuclear waste. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by adsorption. Slovak Republic avails of many significant deposits of bentonites. Adsorption of Cs on five Slovak bentonites of deposits (Jelsový potok, Kopernica, Lieskovec, Lastovce and Dolna Ves) has been studied with the use of batch technique. In the case of Dolna Ves deposit, the mixed-layer illite–smectite has been identified as the main clay component. Natural and irradiated samples, in two different kinds of grain size: 45 and 250 μm have been used in the experiments. The adsorptions of Cs on bentonite under various experimental conditions, such as contact time, adsorbent and adsorbate concentrations have been studied. The Cation Exchange Capacity values for particular deposits drop in the following order: Jelsový potok > Kopernica > Lieskovec > Lastovce > Dolna Ves. Bentonites irradiated samples with 390 kGy have shown higher specific surface and higher values of the adsorption capacity. Distribution coefficients have been determined for bentonite-cesium solution system as a function of contact time and adsorbate and adsorbent concentration. The data have been interpreted in terms of Langmuir isotherm. The uptake of Cs has been rapid and the adsorption of cesium has increased with increasing metal concentrations. The adsorption percentage has decreased with increasing of metal concentrations. Adsorption of Cs has been suppressed by presence of Ca2+ more than Na+ cation. Sorption experiments carried out show that the most suitable materials intended for use as barriers surrounding a canister of spent nuclear fuel are bentonites of the Jelsový potok and Kopernica deposits.

Rapid separation method for emergency water and urine samples.

Abstract: The Savannah River Site Environmental Bioassay Lab participated in the 2008 NRIP Emergency Response program administered by the National Institute for Standards and Technology (NIST) in May, 2008. A new rapid column separation method was used for analysis of actinides and 90Sr in the NRIP 2008 emergency water and urine samples. Significant method improvements were applied to reduce analytical times. As a result, much faster analysis times were achieved, less than 3 hours for determination of 90Sr and 3–4 hours for actinides. This represents a 25%–33% improvement in analysis times from NRIP 2007 and a ∼100% improvement compared to NRIP 2006 report times. Column flow rates were increased by a factor of two, with no significant adverse impact on the method performance. Larger sample aliquots, shorter count times, faster cerium fluoride microprecipitation and streamlined calcium phosphate precipitation were also employed. Based on initial feedback from NIST, the SRS Environmental Bioassay Lab had the most rapid analysis times for actinides and 90Sr analyses for NRIP 2008 emergency urine samples. High levels of potential matrix interferences may be present in emergency samples and rugged methods are essential. Extremely high levels of 210Po were found to have an adverse effect on the uranium results for the NRIP-08 urine samples, while uranium results for NRIP-08 water samples were not affected. This problem, which was not observed for NRIP-06 or NRIP-07 urine samples, was resolved by using an enhanced 210Po removal step, which will be described.

Adsorption of uranium(VI) onto Ulva sp.-sepiolite composite

Abstract: Ulva sp. and sepiolite were used to prepare composite adsorbent. The adsorption of uranium(VI) from aqueous solutions onto Ulva sp.-sepiolite has been studied by using a batch adsorber. The parameters that affect the uranium(VI) adsorption, such as solution pH, initial uranium(VI) concentration, and temperature, have been investigated and the optimum conditions determined. The adsorption patterns of uranium on the composite adsorbent followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms. The Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models have been applied and the data correlate well with Freundlich model. The sorption is physical in nature (sorption energy, E = 4.01 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK d vs. 1/T plots. Thermodynamic parameters (ΔH ads = −22.17 kJ/mol, ΔS ads = −17.47 J/mol·K, ΔG o ads (298.15 K) = −16.96 kJ/mol) show the exothermic heat of adsorption and the feasibility of the process. The results suggested that the Ulva sp-sepiolite composite adsorbent is suitable as a sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.

Characterizing air particulate matter composition and sources in Lisbon, Portugal

Abstract: The goal of this research is to determine trends and sources of airborne particulates in the centre of Lisbon, by using speciated particulate-matter data and back-trajectory analyses. Results showed that, in 2007, the annual PM2.5 concentration exceeded the World Health Organization recommended levels. PM2.5 diurnal variability and the ratio between weekdays’ and weekends’ concentrations indicated that traffic contributed highly to decreasing air quality. Air back-trajectory analysis showed that maritime air mass transport had a significant role on air quality in Lisbon, promoting the decrease of anthropogenic aerosol concentrations.

Analyses of radionuclides in soil, water, and agriculture products near the Urgeiriça uranium mine in Portugal.

Abstract: Analyses of soils, irrigation waters, agriculture products (lettuce), green pasture, and cheese were performed in samples collected in the area of the old Urgeirica uranium mine and milling facilities, Centre-North of Portugal, in order to assess the transfer of uranium series radionuclides in the environment and to man. Soils close to milling tailings display an enhancement of radioactivity. In the drainage basin of the stream Ribeira da Pantanha, receiving drainage from the tailings piles and discharges from the acid mine water treatment plant, there was enhancement of uranium series radionuclide concentrations in water and suspended matter. Agriculture products from kitchen gardens irrigated with water from the Ribeira da Pantanha show an increase of radioactivity, mainly due to uranium isotopes. Agriculture products from other kitchen gardens in this area, irrigated with groundwater, as well pasture and cheese produced locally from sheep milk did not show enhanced radionuclide concentrations. In the Urgeirica area, some soils display radionuclide concentrations higher than soils in reference areas and, in agriculture products grown there, 226Ra was the radionuclide more concentrated by vegetables. Through ingestion of these products 226Ra may be the main contributor to the increment of radiation dose received by local population.

Anion analysis in uranium ore concentrates by ion chromatography

Abstract: In the present exploratory study, the applicability of anionic impurities for attributing nuclear material to a certain chemical process or origin has been investigated. Anions (e.g., nitrate, sulphate, fluoride, chloride) originate from acids or salt solutions that are used for processing of solutions containing uranium or plutonium. The study focuses on uranium ore concentrates (“yellow cakes”) originating from different mines. Uranium is mined from different types of ore body and depending on the type of rock, different chemical processes for leaching, dissolving and precipitating the uranium need to be applied. Consequently, the anionic patterns observed in the products of these processes (the “ore concentrates”) are different. The concentrations of different anionic species were measured by ion chromatography using conductivity detection. The results show clear differences of anion concentrations and patterns between samples from different uranium mines. Besides this, differences between sampling campaigns in a same mine were also observed indicating that the uranium ore is not homogeneous in a mine. These within-mine variations, however, were smaller than the between-mine variations.

A new method for the determination of plutonium and americium using high pressure microwave digestion and alpha-spectrometry or ICP-SMS

Abstract: Plutonium and americium are radionuclides particularly difficult to measure in environmental samples because they are α-emitters and therefore necessitate a careful separation before any measurement, either using radiometric methods or ICP-SMS. Recent developments in extraction chromatography resins such as Eichrom® TRU and TEVA have resolved many of the analytical problems but drawbacks such as low recovery and spectral interferences still occasionally occur. Here, we report on the use of the new Eichrom® DGA resin in association with TEVA resin and high pressure microwave acid leaching for the sequential determination of plutonium and americium in environmental samples. The method results in average recoveries of 83 ± 15% for plutonium and 73 ± 22% for americium (n = 60), and a less than 10% deviation from reference values of four IAEA reference materials and three samples from intercomparisons exercises. The method is also suitable for measuring 239Pu in water samples at the μBq/l level, if ICP-SMS is used for the measurement.

Resuspension of radionuclides into the atmosphere due to forest fires

Abstract: Two major wild fire episodes occurred in north- western Russia in April/May and August 2008. The burning biomass and heating of the surface soil released several hazardous components into the atmosphere. During the spring smoke episode the 137 Cs activity concentration in the air in southern Finland increased by a factor of 10 compared to values just before the episode. Simultaneously there was an increase of a same order of magnitude in the concentra- tions of PM10, trace metals (e.g. lead), polycyclic aromatic hydrocarbons (e.g. benzo(a)pyrene) and potassium. The 210 Po/ 210 Pb activity ratio increased from the usual 3-5% to even as high as 35% because Po is more volatile than Pb. The summer episode was less severe but still the mercury concentration in the air increased by a factor of two while 137 Cs activity concentration rose by a factor of eight. From the radiological point of view the exposure to the increased radionuclide concentration was insignificant compared to health hazards due to the increased concentration of aerosol particles and their chemical components.

Electrode processes of uranium ions and electrodeposition of uranium in molten LiCl-KCl

Abstract: In the first part, LiCl-KCl-UCl3 and LiCl-KCl-UCl3-UCl4 molten salts were prepared, which were studied employing cyclic voltammetry and chronopotentiometry techniques, respectively. It was determined that the reduction of U(IV) to uranium metal takes two steps. Firstly, U(IV) is reduced to U(III). Then, the reduction of U(III) to uranium metal occurs in a step with a global exchange of three electrons. Cyclic voltammetry studies indicated that at low sweep rates, the reduction of U(III) to uranium is reversible. However, a mixed control of both diffusion and electrontransfer is observed as the sweep rate increases. The diffusion coefficient of U(III) and the formal potential of U(III)/U versus Ag/AgCl reference electrode in these two salt systems were calculated respectively. In second part, based on the data of the electrode processes of uranium ions, electrodeposition of uranium metal was carried out. Uranium deposits were prepared adopting a 304 stainless steel electrode in the molten LiCl-KCl-UCl3 and LiCl-KCl-UCl3-UCl4, respectively by employing suitable electrolytic techniques. The morphology of the deposits and the cross-section of the cathode were investigated by SEM. It was determined that at the beginning of the deposition process, uranium product alloys with stainless steel and forms a thin layer, and then uranium begins to grow adhering to the layer.

Extraction of microamounts of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of diphenyl-N-butylcarbamoylmethyl phosphine oxide

Abstract: Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of diphenyl-N-butylcarbamoylmethyl phosphine oxide (DPBCMPO, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, HL2+, ML23+, ML33+ and ML43+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuLn3+ and AmLn3+, where n = 2, 3, 4 and L is DPBCMPO, in water saturated nitrobenzene are comparable.

Rapid method for determination of radiostrontium in emergency milk samples

Abstract: A new rapid separation method for radiostrontium in emergency milk samples was developed at the Savannah River Site (SRS) Environmental Bioassay Laboratory (Aiken, SC, USA) that will allow rapid separation and measurement of Sr-90 within 8 hours. The new method uses calcium phosphate precipitation, nitric acid dissolution of the precipitate to coagulate residual fat/proteins and a rapid strontium separation using Sr Resin (Eichrom Technologies, Darien, IL, USA) with vacuum-assisted flow rates. The method is much faster than previous method that use calcination or cation exchange pretreatment, has excellent chemical recovery, and effectively removes beta interferences. When a 100 ml sample aliquot is used, the method has a detection limit of 0.5 Bq/L, well below generic emergency action levels.

Extractive distribution of microamounts of europium and americium in the two phase water — HCl — nitrobenzene — N,N,N′,N′-tetraethyl-2,6-dipicolinamide — hydrogen dicarbollylcobaltate system

Abstract: Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of N,N,N′,N′-tetraethyl-2,6-dipicolinamide (TEtDPA, L) has been investigated. The equilibrium data have been explained assuming that the cations HL+, HL23+, ML23+ and ML33+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuLn,org3+ and AmLn,org3+, where n = 2, 3 and L is TEtDPA, in the mentioned medium are comparable.

Low level detection of 135Cs and 137Cs in environmental samples by ICP-MS

Abstract: The measurement of fission product cesium isotopes 135Cs and 137Cs at low femtogram (fg) 10−15 levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for 135Cs was 2 fg/mL (0.1 μBq/mL) and for 137Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.

Evaluating children exposure to air pollutants for an epidemiological study

Abstract: Recent health studies evidence that epidemiological studies must be combined with accurate analyses of the physico-chemical properties of the particles in order to determine the effects of atmospheric aerosols on human health. The project “Atmospheric Aerosol Impacts on Human Health” focuses on the chemical characterization of PM2.5 aerosols with the aim to analyze the health risks associated with exposure to aerosols and understand how their chemical composition contributes to the toxicity and human health problems traditionally associated with fine particles. During one year, PM2.5 was collected daily, with a Partisol sampler, in the centre of Lisbon. The aerosols were analyzed by Neutron Activation Analysis and Ion Chromatography in order to determine their chemical composition. In parallel the clinical situation of students from the schools situated around the sampler was followed. The incidence of asthma and rhinitis episodes was registered. Results showed that students were exposed to PM2.5 concentrations that exceed the World Health Organization recommended levels. A marked sea influence in the aerosol characteristics was identified by the use of air masses trajectories and by the concentrations of chloride, sodium and magnesium.

Radioactivity in the Baltic Sea: inventories and temporal trends of 137Cs and 90Sr in water and sediments

Abstract: The Baltic Sea is ecologically unique as one of the world's largest brackish water basins. It was signifi- cantly contaminated by radioactivity following the Cher- nobyl accident in 1986, the major contaminant being long- lived 137 Cs. Due to the slow exchange of water between the Baltic Sea and the North Sea and the relatively rapid sed- imentation rates, radionuclides have prolonged residence times in the Baltic Sea. 137 Cs levels are consequently still clearly higher than in other water bodies around the world. In addition to the Chernobyl accident, artificial radionuc- lides in the Baltic Sea originate from the global fallout following nuclear weapons testing in the 1950s and 1960s, while discharges into the Baltic Sea from nuclear power plants and other facilities are of minor importance. Here, inventories and the temporal evolution of radionuclides both in seawater and sediments of the Baltic Sea are pre- sented and discussed.

Extraction of microamounts of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of N,N′-dibutyl-N,N′-dimethyl-2-(2-dodecyloxyethyl)-malonamide

Abstract: Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H + B – ) in the presence of N,N'-dibutyl-N,N'-dimethyl-2-(2-dodecyloxyethyl)-malonamide (DBDMDDOEMA, L) has been investigated. The equilibrium data have been explained assuming that the cations HL2 , ML2 and ML3 (M 3+ = Eu 3+ , Am 3+ ) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuLn and AmLn , where n = 2,3 and L is DBDMDDOEMA, in water saturated nitrobenzene are comparable.

Design and construction of a low-background, internal-source proportional counter

Abstract: High-purity copper has emerged as a preferred construction material for ultra-low-background HPGe spectrometers and offers excellent bulk radiopurity along with good electrical, thermal, and vacuum properties. Recently, these materials and techniques have been applied to the construction of low-background internal-source gas proportional counters. This work describes the design, construction, and testing of an ultra-low-background internal-source gas proportional counter built primarily of high purity electroformed copper. Energy resolution of ~10% FWHM at 59.5 keV has been achieved, a low-energy threshold of ~3 keV has been reached, and gas gain stability over a 4-week period has been demonstrated. Progress toward low-background operation is described.

Production of 88,89Zr by proton induced activation of natY and separation by SLX and LLX

Abstract: nat Y foil was irradiated by 20 MeV proton to produce no-carrier-added 88,89 Zr. A comparative evaluation on radioanalytical separation methods of 88,89 Zr was car- ried out from irradiated target matrix by both liquid-liquid (LLX) and solid-liquid (SLX) extraction methods using di-(2-ethylhexyl) phosphoric acid (HDEHP) dissolved in cyclohexane as liquid cation exchanger and Dowex 50W- X8 H ? form (20-50 mesh) as solid cation exchanger. Both the methods offer good separation and high yield of nca 88,89 Zr but SLX offers much higher separation factor and

Metal contamination in urban park soils of São Paulo

Abstract: There has been little research on metal concentration levels in urban soils of Sao Paulo, a city with 19 million inhabitants with severe pollution problems. In the present study, the concentration of As, Ba, Cr, Cu, Pb, Sb and Zn, were determined by INAA and XRF in surface soil samples from 7 public parks located within Sao Paulo city. The results obtained showed that soils of Sao Paulo public parks present concentration levels of the studied elements higher than the reference values for soils in Sao Paulo State. Traffic related elements such as Cu, Pb and Zn presented high concentrations in parks located near avenues of highly dense traffic and may be associated to vehicular sources.