Showing papers in "Journal of Radioanalytical and Nuclear Chemistry in 1994"

Polonium-210 and lead-210 in marine organisms: Intake levels for Japanese

Abstract: The concentrations of210Po and210Pb were determined in about 30 species of marine organisms collected mainly from the north-easterm region of Japan to know the levels and distributions of these radionuclides and to estimate their intake levels from marine foods.210Po and210Pb showed a wide range of concentration in species: 0.6–26 and 0.04–0.54 Bq/kg (wet wt) in fishes, 0.5–220 and 0.2–43 Bq/kg (wet wt) in molluscs, echinoderms and chordatas, and 2.8–4.3 and 0.4–1.3 Bq/kg (wet wt) in algae, respectively. Higher accumulation of210Po relative to210Pb was found in all of the samples analyzed. The intake levels of210Po and210Pb by marine foods consumption were roughly estimated to be 0.48–0.69 and 0.022–0.042 Bq/d per person, respectively, on the basis of the statistical data on the consumption of seafood and/or production rates of marine foods.

The use of a modified Westcott-formalism in the ko-standardization of NAA: The state of affairs

Abstract: Recently, the introduction was proposed of the Westcott-formalism in the ko-standardization method, in order to enable the handling of analytically important “non-1/v” (n, γ) reactions. In the present paper some elucidations are given to the “Westcott-based”k o-method: the black box of Westcott's “g+rs” formalism is opened; procedures and formulas are given for the experimental determination of the flux parameters and a survey is presented of the status of the nuclear data.

Sourcing archaeological obsidian by an abbreviated NAA procedure

Abstract: An abbreviated NAA procedure has been developed to fingerprint obsidian artifacts in the Mesoamerican region. Despite the large number of available sources, an NAA procedure, which relies on producing short-lived isotopes, has been applied with a success rate greater than 90 percent. The abbreviated NAA procedure is rapid and cost competitive with the XRF technique more often applied in obsidian sourcing. Results from the analysis of over 1,200 obsidian artifacts from throughout Mesoamerica are presented.

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra, and210Pb. in environmental samples

Abstract: A sequential analytical method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra and210Pb in environmental samples was developed Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer Radium isotopes and210Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate Radium-226 is determined by gross alpha counting of the final BaSO4 precipitate and228Ra by gross beta counting of the same source Lead-210 is determined through beta counting of its daughter product210Bi

The atmospheric deposition of major, minor and trace elements within and around three cement factories

Abstract: Total atmospheric deposits of particulate matter within the premises of three Nigerian cement factories were collected and characterised for about 25 elements using a combination of Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF) and Instrumental Neutron Activation Analysis (NAA). Some toxic heavy metals like As, Pb, Ni, Co, Zn, Cu, Cr, as well as S, Ca, P were found to be highly enriched in the neighbourhood compared to the control sites. Deposition rates of the cement marker element, Ca, decreased exponentially with increasing distance from the factories.

Separation of carrier-free lutetium-177 from neutron irradiated natural ytterbium target

Abstract: Neutron irradiation of naturally occurring Yb produces small amounts of carrier-free177Lu activity. Cation exchange chromatography in the displacement development mode using Dowex-50X8, 200–400 mesh resin, and Zn2+ as the separating ion was used to separate177Lu produced in a neutron irradiated Yb target. 0.04M α-hydroxyisobutyric acid at pH 4.6±2 and temperature 26±1°C was used to elute carrier-free177Lu in 70% yield and at a radionuclidic purity greater than 99%.

Characterization of plutonium contamination at the former nuclear weapons testing range, at Maralinga in South Australia

Abstract: Re-suspension studies on soils contaminated with plutonium during nuclear weapons tests were performed by use of a mechanical dust-raising apparatus. Airborne dust was analyzed in terms of mass and241Am activities for particle sizes less than 7 μm. The AMAD was determined as 4.8 to 6 μm, for re-suspended soil. Also, surface soil was characterized in the laboratory by means of sieving and microparticle classification, yielding mass and241Am activity distributions with respect to size. Data indicate the granularity of plutonium contamination at both major and minor trial sites. Depth profile analyses for undisturbed, areas demonstrate that most (74% on average) of the americium and plutonium activity is found in the top 10 mm of soil. Plutonium and americium activities were found to be enhanced in the inhalable fraction over their values, in the total soil, and the enhancement factors were similar in re-suspended dust and surface soil. Observed enhancement factors ranged from 3.7 to 32.5.

Compton suppression neutron activation methods in environmental analysis

Abstract: An overview of Compton suppression neutron activation analysis (NAA) is given. The basic theory of the technique, its experimental design, uniqueness, and limitations are discussed. Experimental data showing its usefulness for the low level determination of several key elements in environmental samples that can not be obtained using conventional non-destructive neutron activation is deliberated.

Thermoluminescence analysis for testing the irradiation of spices

Abstract: Thermoluminescence signals of irradiated and unirradiated spices and herbs are due to inorganic matter grains adhering to the surfaces. This study reports the mineral composition of this dust being, mainly quartz, calcite and philosilicates; it shows the differences between samples exposed and non-exposed to γ-radiation on the basis of TL signals after long storage periods (1–16 months). A saturation process in the TL signal is found when the samples absorb doses higher than 5 kGy. Finally, the TL glow curve intensities do not suffer significant changes with the dose rate of the γ-source used in the radiation process.

Sorption of radioiodine on organic rich soil, clay minerals and alumina

Abstract: Batch method was used to investigate the sorption behavior of radioiodine on organic rich soil, alumina, chlorite-illite clay mixture and bentonite.131I was used as tracer. The grain sizes of the samples used were all below 38 μm. A rather slow kinetics was observed for the adsorption of radioiodine on organic rich soil. The distribution ratio increased with increasing solution/solid (V/m) ratio, and the contact time. The pH of the synthetic groundwater did not change the distribution ratio appreciably. The soil biomass however, showed a striking effect on the adsorption of radioiodine. Among the clay minerals, the highest distribution ratio value was found for chlorite-illite clay mixture. All the values were however well below those of the organic rich soil. The sorption data were fitted to Freundlich and Dubinin-Radushkevich types isotherms. Means energies of adsorption, as well as the affinity ratios of the sorption sites to iodine and chlorine were calculated.

An improved tungsten-188/rhenium-188 gel generator based on zirconium tungstate

Abstract: An improved188W-188Re gel generator based on Zr tungstate is described. The influence of synthesis parameters and pre-treatment conditions on188Re elution yields and the188W breakthrough was studied with 0.15M aqueous solution of NaCl at pH 5.3 to 7.3 as well as with some organic solvents. An elution efficiency of 80% was achieved during 3 month of explotation with 0.15M NaCl at pH=6.3. The188W breakthrough was 10−4 to 10−3%. The188W breakthrough may be decreased to 10−6% when converted into tandem generator with an alumina column. However,188Re yields are reduced by 8–12% with a tandem generator.

Organophosphinic, phosphonic acids and their binary mixtures as extractants for molybdenum(VI) and uranium(VI) from aqueous HCl media

Abstract: Extraction studies of uranium(VI) and molybdenum(VI) with organophosphoric, phosphinic acid and its thiosubstituted derivatives have been carried out from 0.1–1.0M HCl solutions. The extracted species are proposed to be UO2R2 and MoO2 CIR on the basis of slope analysis for uranium(VI) and molybdenum(VI), respectively. The extraction efficiencies of PC-88A, Cyanex 272, Cyanex 301 and Cyanex 302 in the extraction of molybdenum(VI) and uranium(VI) are compared. Synergistic effects have been studied with binary mixtures of extractants. Separation of molybdenum(VI) from uranium(VI) is feasible by Cyanex 301 from 1M HCl, the separation factor log βbeing 2.3.

Extraction of europium and americium by a mixture of CMPO and dicarbollide

Abstract: The extraction of Eu3+ and Am3+ by a mixture of CMPO and dicarbollide in nitrobenzene has been studied. The synergetic effect of dicarbollide is pronounced at low acidities but still lower than for previously studied DBDECMP. Separation properties towards Am/Eu pair are small.

Neutron scattering by hydrogen in cold neutron prompt gamma-activation analysis

Abstract: The effects of neutron scattering by hydrogen within targets for cold neutron prompt γ-ray activation analysis (CNPGAA) have been characterized. For most targets studied, the probability for neutron absorption, and hence CNPGAA sensitivities (counts·s−1·mg−1), decrease with increasing H content and with target thickness. Comparisons with results from thermal neutron PGAA indicate that the effects of cold neutron scattering differ from those of thermal neutron scattering. CNPGAA sensitivities for “l/v” nuclides show similar sensitivity decreases, while Sm sensitivities show smaller decreases.

Concentration levels of rare-earth elements and thorium in plants from the morro do ferro environment as an indicator for the biological availability of transuranium elements

Abstract: Plants and soils from a natural thorium and rare-earth element occurrence (Morro do Ferro, Brazil) were analyzed by alpha spectrometry (Th) and ICP-AES (REE), after pre-concentration of the elements by solvent extraction, co-precipitation and ion exchange procedures. Leaching experiments with humic acid solutions and different soils were performed to estimate the fraction of elements biologically available. High concentrations of the light rare-earth elements (LREE) and of Th, reaching some hundreds of μg/g-ash, were measured in plant leaves from the areas of the highest concentration of these elements in soil and in near-surface waters. Chondrite normalized REE plots of plant leaves and corresponding soils are very similar, suggesting that there is no significant fractionation between the REE during uptake from the soil solution and incorporation into the leaves. However, Ce-depletion was observed for some plant species, increasing forSolanum ciliatum in the sequence: leaves

Measuring hydrogen by cold-neutron prompt-gamma activation analysis

Abstract: By irradiating with cold neutrons and avoiding hydrogenous materials of construction, we have developed a PGAA instrument at the Cold Neutron Research Facility at NIST with hydrogen detection limits in the microgram range in many materials. Quantities of 5–10 μg H/g are presently measurable in gram-sized samples of silicon or quartz, and of order 0.01 wt % can be quantitatively measured in complex silicate rocks.

Trace elements in Australian opals using neutron activation analysis

Abstract: Neutron activation analysis was used to determine the concentration of trace elements in 42 samples of black, grey and white opals taken from a number of recognised Australian field. The results were evaluated to determine if a relationship existed between trace element content and opal colour.

Study on the contents of trace rare earth elements and their distribution in wheat and rice samples by rnaa

Abstract: The concentrations of 8 REE (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in wheat and rice samples have been determined by RNAA. The contents and distributions of REE in each part of the plants (i.e. root, leaf, stem, husk and seed) and their host soils were studied, which included samples applied with rare earch elements in farming and control samples. The effects of applying rare earths on the uptake of REE by the plants and the REE accumulation in the grains on human health were also discussed in this paper.

A comparison of instrumental neutron activation analysis and inductively coupled plasma-mass spectrometry for trace element determination in petroleum geochemistry

Abstract: INAA and ICP-MS methods for determining trace elements in crude oils, oil fractions and sourcerock bitumens are compared. Results for a wide variety of crude oil types show good agreement for many elements for which the two techniques are suited and which are geochemically important (e.g., Ni, V, Fe, Se, As, etc.). For some other elements, the two techniques are complementary (e.g., B, Be, Cd, Br). The advantages and disadvantages of INAA and ICP-MS in geochemical exploration programs are reviewed and practical examples presented.

Heavy metal uptake by zeoliferous rocks from Metaxades, Thrace, Greece : an exploratory study

Abstract: The uptake of mercury, cadmium and silver from aqueous solutions by unpretreated and NaCl-pretreated clinoptilolite-bearing volcaniclastic rocks from Metaxades (Thrace, Greece) has been studied using a batch method with radioactive tracers (197Hg,115Cd and110mAg). The concentration of the solutions used varied between approximately 1000 and 17000 ppm. An improvement of the uptake ability was observed in the case of NaCl-pretreated material for all the investigated metals and especially for mercury at the upper part of the concentration range studied. The heavy metal uptake is attributed to different mechanisms taking place both at the rock grains and their individual mineral components.

Determination of Np, Pu and Am in high level radioactive waste with extraction-liquid scintillation counting

Abstract: A new method for the determination of transuranium elements, Np, Pu and Am with extraction-liquid scintillation counting has been studied systematically. Procedures for the separation of Pu and Am by HDEHP-TRPO extraction and for the separation of Np by TTA-TiOA extraction have been developed, by which the recovery of Np, Pu and Am is 97%, 99% and 99%, respectively, and the decontamination factors for the major fission products (90Sr,137Cs etc.) are 104–106. Pulse shape discrimination (PSD) technique has been introduced to liquid scintillation counting, by which the counting efficiency of α-activity is >99% and the rejection of β-counts is >99.95%. This new method, combining extraction and pulse shape discrimination with liquid scintillation technique, has been successfully applied to the assay of Np, Pu and Am in high level radioactive waste.

The speciation of arsenic in seawater and marine species

Abstract: Dissolved inorganic arsenic species were determined in natural waters and selected marine species. Prior to irradiation by NAA samples were preconcentrated and the As(III) and As(V) species separated by APCDT-chloroform extraction. Marine samples were digested by microwave heating. Interpretation of data was achieved by comparing the ratio of As(III)/As(V) in the samples and correlating it with the prevailing environmental conditions.

Solvent extraction mechanism of pertechnetate with tetraphenylarsonium chloride

Abstract: A systematic study of extraction of pertechnetate with tetraphenylarsonium chloride (TPAC) in chloroform from aqueous chloride solutions has been carried out at 25°C at ionic strength of 1.0. Fundamental parameters governing the distribution equilibrium of TPAC were determined. Extraction behavior of pertechnetate was established on the basis of the distribution mechanism of TPAC.

On-line gas chemistry experiments with transactinide elements

Abstract: Recent experiments are reviewed which used on-line isothermal gas chromatography techniques for studying chemical properties of transactinide elements. In these experiments the volatilities of chloride and bromide molecules in quartz columns were investigated. Measured chromatograms obtained with single molecules are shown to be correlated with the vapor pressure of the corresponding macroamounts. All existing data reveal that element 104 (rutherfordium) chloride has a volatility resembling very much those of the chlorides from the homologous elements hafnium and zirconium. For element 105 (hahnium) a surprisingly low volatility of the bromide compound, is found if compared to those of the corresponding bromides from the homologous elements tantalum and niobium. This latter experimental observation contrasts relativistic theoretical calculations which would predict a higher volatility for hahnium bromide if compared to those of tantalum and niobium bromides.

Concentrations of thorium and uranium in freshwater samples collected in the former USSR

Abstract: Approximately 100 freshwater samples were collected in Ukraine, Russia, and Belorussia with regard to the Chernobyl accident. Thorium and uranium were determined by both quantitative and semiquantitative analysis modes of inductively coupled plasma mass spectrometry (ICP-MS). Thorium-232 was detected in only a few samples. Uranium concentrations ranged from non-detectable to 1,000ng/ml. Mean and median concentrations of238U were found to be 30.7±139 and 0.7 ng/ml, respectively. The isotope ratio of234U/238U ranged from 4.6·10−5 to 4.4·10−4. Mean ratio of235U/238U was 0.00721±0.00006 (n=27).

Extraction of U(VI), Th(IV) and some fission products from nitric acid medium by sulfoxides and effect of γ-irradiation on the extraction

Abstract: The extracting abilities for thorium, uranium and some fission products by five sulfoxides are given. The results show that di(2-ethylhexyl) sulfoxide (DEHSO) is not only completely miscible with kerosene, but also superior to tri-n-butyl phosphate in some properties. The extraction behavior of uranium, thorium and some fission products such as zirconium, niobium and ruthenium from aqueous nitric acid with DEHSO in kerosene has been studied over a wide range of conditions. DEHSO extracted uranium and fission products better than TBP under all conditions and is similar to TBP in extraction of thorium. A study of extraction mechanism indicates that U and Th are extracted as disolvates, whereas HNO3 is extracted as monosolvate. Extraction of the two actinides decreases with increasing temperature, indicating the extraction to be exothermic. Preliminary studies show that γ-ray irradiated DEHSO extracts Zr and Nb to a smaller extent than irradiated TBP in the range of 104–107 rad.

Use of amorphous zirconium phosphate for the treatment of radioactive waste

Abstract: This paper reports some ion-exchange column experiments, carried out to determine the breakthrough curves of137Cs and89Sr radioisotopes on a commercially available inorganic ion-exchange sorbent of the amorphous zirconium phosphate type. A dynamic capacity of about 3–4 meq·g−1 was observed.

Effect of γ-irradiation on the catalytic activity and selectivity of γ-alumina II. Conversion of isopropanol

Abstract: The catalytic conversion of isopropanol was conducted over a poorly crystalline γ-alumina irradiated with different doses of γ-rays (25–150 Mrad). The catalytic reaction was carried out at 180–400°C in a flow technique under atmospheric pressure. The results showed that the dose of 25 Mrad resulted in a decrease of about 50% of the dehydration activity which suffered a further slight decrease upon irradiation at a dose of 50 Mrad. Increasing the dose in the range of 50–150 Mrad effected an increase in the dehydration activity reaching a maximum limit at 100 Mrad, then decreased abruptly by a dose of 150 Mrad. γ-irradiation led also to creation of some active sites contributing in dehydrogenation of isopropanol to producing acetone. These results were discussed in terms of removal of Bronsted acidity (25–50 Mrad), responsible for the dehydration reaction and to transformation of Lewis to Bronsted acidity (100 Mrad) by the action of liberated water from the dehydration reaction. The drop in dehydration activity due to irradiation at 150 Mrad might result from an efficient removal of the Bronsted acid sites created. The induced dehydrogenation activity of irradiated aluminas was attributed to creation of some electron-donor centers.

Adsorption of low level51Cr(VI) from aqueous solution by bismuth trioxide: Kinetic and IR study

Abstract: Radiotracer technique has been used for the investigation of adsorption of chromium (VI) traces on bismuth trioxide from aqueous solution. The effect of pH (2–10), concentration of chromate solution (10−6–10−2M) and temperature (303–323 K) has been thoroughly investigated. The influence of certain foreign ions has also been studied. The calculated kinetic and thermodynamic parameters indicate the first order rate law, spontaneity and exothermic nature of the adsorption process. Further, IR studies have established the chemical interaction between the sorbate and sorbent and a possible mechanism of the sorption process based on ligand exchange has been proposed.

NADA92: An automated, user-friendly program for neutron activation data analysis

Abstract: We have developed a highly automated program for the analysis of data from neutron activation analysis (NAA). Spectral analysis is done using almost any common MCA employing regions of interest or peak-fitting routine of the user's choice. A wide variety of data entry possibilities is available, from fully manual data entry to an automatic mode where the user enters all necessary data in a tabular format and the computer calculated the results. The resulting data can be automatically imported into a LOTUS 1-2-3 compatible spreadsheet for statistical analysis. All of the features of previous versions of NADA have been retained. These include a variety of methods for dead-time correction, correction of spectral and nuclear interferences, and a complete, concise hard-copy output. Future improvements include a routine which will automatically select regions-of-interest for spectra in ORTEC Maestro, thus reducing the processing time needed.