Instrumental neutron activation analysis of air filter samples

Résumé La mesure de traces d'éléments dans l'air ambiant a fait l'objet d'une attention accrue ces derniers mois, en raison d'un intérêt grandissant pour les dangers en puissance pour la santé, qui résultent de l'exposition prolongée à certaines substances toxiques. L'analyse par activation neutronique a été employée avec succès dans la recherche de traces d'éléments, et ce, pour un grand nombre d'études de l'environnement; elle semble convenir de fa?on idéale pour la détermination non-destructive multi-élémentaire de la composition de milieux de particules portées par l'air. Dans cet article, on rend compte des performances de l'analyse instrumentale par activation neutronique comme on le montre dans le cas de 40 échantillons d'air filtrées provenant d'une zone métropolitaine.      

Instrumental neutron activation analysis of carbon containing micro-spheres from Jungfrau-Joch glacier ice

From about 700 kg old, high altitude glacier ice (age 400 y) more than 170 glassy spherical objects with a mean diameter of 100 m were isolated. Neutron activation analysis of individual transparent objects (each 10^–6 g) showed the presence of K, Sc, Cr, Fe, La, Eu, Au, etc., in varying concentrations. A detection limit of 10^–14 g/g was achieved by means of an anticompton circuit. A systematic study by mass spectrometry of positive and negative ions using a LASER microprobe disclosed that the main constituents of some of these smooth glacier spheres consisted of elemental carbon. The chemical composition of some spherules admits the possibility of extraterrestrial origin, e.g. ablation material from meteorites with high carbon contents, which entered the earth's atmosphere.     

Instrumental neutron activation analysis of samples with masses from micrograms to hectograms

The rotating rig at the Danish DR-3 reactor was used for irradiation of samples with masses from a hundred micrograms to several hundred grams. The pneumatic post for uranium delayed neutron counting was used for automatic sequential irradiation of samples subdivided into up to 24 aliquots, each with a volume of 7 cm³. The cumulative samples were measured in polyethylene irradiation containers in a specially designed radial holder.     

Instrumental neutron activation analysis of tungsten in various steel samples

The instrumental neutron activation analysis /INAA/ of tungsten in various steel samples has been done with a 2 Ci²⁵²Cf fission neutron source having an integrated neutron flux of 10¹⁰ ns^–1 and measuring the -activity of¹⁸⁷W on a 4 K multi-channel analyzer /MCA/ coupled to a high purity germanium /HPGe/ detector. The tungsten content of various steel samples was between 0.017 and 0.024%.     

Instrumental neutron activation analysis of samples with volumes from 2 to 350 ml

Usually neutron activation analyses are performed in point-source geometry. However, specially designed irradiation positions and carefully planned measuring conditions enabled the activation and analysis of samples with weights up to several tens of kilograms. A dedicated character of irradiation and of measuring conditions was the main reason for a very limited application of such activation analysis. The use of routine irradiation facilities and standard conditions for analytical gamma-spectrometric measurements is described. Starting with samples of some hundred milligrams usually used in activation, through multi-gram samples to several hundred gram samples, irradiation and measuring conditions were studied and tested for development of the method. This work began in 1991 in Denmark, using the Danish DR-3 reactor. Since then different aspects of the method have been investigated on 6 reactors; in Denmark on DR-3, in Austria on Triga-MkII (in Vienna), and Astra (in Seibersdorf), in the German Federal Republic on FRG-1 in Geesthacht, in Norway on Jeep II (in Kjeller), and in Kazakhstan on VVR-K (in Alatau). Altogether more than 1000 samples have been irradiated and measured. In total, the roughly 30 kg of irradiated materials included almost 300 large samples of more than 30 gram weight. The following theoretical and practical aspects were investigated during the work: theoretical problems concerning neutron self-absorption in common organic and inorganic materials, as well as gamma-attenuation during the measurement. From a more practical point of view: health physics and radiation hazards during irradiation, measurement, transportation and storage of samples with several hundred grams weight. Special requirements to irradiation containers were formulated and various containers were tested. Main advantages and drawbacks of the method are discussed.     

Instrumental neutron activation analysis of large samples: A pilot experiment

A large sample INAA (LS-INAA) was conducted based on available experimental conditions. Four different materials, e.g., a quartz-sand and three wastes from an incineration plant were analyzed on sample size of 1 kg. The neutron flux spatial distribution was determined by irradiation of flux monitors in the sample. The gamma-ray apparent counting efficiency was evaluated based on the effective-solid angle concept, using linear attenuation coefficients calculated from an iteration process. The k ₀- and the modified monostandard methods were modified for the LS-INAA. To check the LS-INAA performance, a conventional small sample INAA was carried out for the quartz sand and a waste. All detected elements in the LS-INAA are presented and the discussion is conducted to explore the sources of errors in the LS-INAA. As a pilot experiment, the information from this work will be used in constructing irradiation and counting devices for the new FRM-II neutron source in Garching, Germany.     

Instrumental neutron activation analysis for multi-elemental determination in Indian tea samples

Instrumental neutron activation analysis (INAA) was employed to determine concentrations of 19 elements (As, Ba, Br, Ce, Co, Cr, Cs, Fe, K, La, Mn, Na, Nd, Rb, Sc, Sm, Th, Yb and Zn) in a large number (55) of tea samples (from market as well as virgin tea leaves) from different locations in India (Assam, Darjeeling, Munnar and Kangra). The results obtained in the present work are compared with those reported in literature. The concentration levels, their variations with collection locations and the correlations among different elements in these samples are discussed.     

Instrumental neutron activation analysis of geological and pedological samples. Further investigation of epithermal neutron activation analysis using monostandard method

A comparative study is presented on neutron activation analysis of rock and soil samples using whole reactor neutron spectrum and epithermal neutrons with both relative and monostandard procedures. The latter procedure used with epithermal neutron activation analysis of soil samples necessitated the use of the “effective resonance integrals” which were determined experimentally. The incorporation of the β factor, representing deviation of reactor epithermal neutron flux from 1/E law, is developed in the present work. The main criteria for the choice of one or more of the procedures studied for a given purpose are also indicated. Analysis of 15 trace elements, Ca and Fe in the standard Japanese granite JC-1 using monostandard epithermal neutron activation gave results in good agreement with the average literature values. This paper is dedicated to the 80th birthday of Professor Dr. Robert Klement, University of Munich.     

Instrumental neutron activation analysis of manganese in some industrially important steel samples

The manganese content of some industrially important steel samples viz. IS-226, spring steel, galvanized iron, high tensile steel, and mild steel is determined by instrumental neutron-activation analysis using a²⁵²Cf neutron source. The analysis is performed by measuring the activity of⁵⁶Mn after /n, / reaction on a 4 k multichannel analyzer coupled to a NaI/Tl/ detector at 847 keV, as well as on a single channel analyzer on integration mode coupled to a NaI/Tl/ detector. The results obtained by both procedures show reasonably good agreement with each other.     

Instrumental neutron activation analysis of environmental samples using thek 0-standardization method

The use of thek ₀-standardization method in instrumental neutron activation analysis gives good accuracy and precision. The analysis time can be reduced drastically by employing software for thek ₀-standardization calculations. In this work samples were irradiated in a TRIGA reactor and the gamma spectrum was analysed by Sampo 90 and thek ₀-standardization by the KAYZERO/SOLCOI code (DSM Research). The efficiency measurement and the peak to total ratio at the reference and other geometries were measured and tested for their accuracy by analysing some reference materials. Reference materials such as SRM 1572 (Citrus leaves), SRM 1573 (Tomato leaves), SRM 1575 (Pine needles), IAEA Soil-7 (Soil) and SRM 1646 (Estuarine sediment) were analysed for the major, minor and trace element contents. The results were in good agreement with the certified or literature values. The recently released IAEA 140 (Sea plant homogenates) was also analysed for 28 elements.     

Instrumental neutron activation analysis of sediment reference materials using the k0-standardization method

An instrumental neutron activation analysis technique has been developed for the determination of As, Au, Ba, Co, Cr, Fe, Hf, Sb, Ta, Th, U, W and Zn in large (10–15 g) geological samples using in-pool irradiation with a SLOWPOKE-2 reactor. The technique allows for the simultaneous irradiation of multiple samples using a neutron flux of between 4·10¹³ and 8·10¹³ n·m^–2·s^–1. The detection limits obtained using the analytical methodology described in this paper are acceptable for exploration geochemistry and the technique has been used to analyze samples collected as part of a metallic minerals survey of Jamaica.     

Instrumental neutron activation analysis of Moroccan geological samples using the k0-standardization method

Instrumental neutron activation analysis (INAA) for traces and major elements of several geological samples from “Zgounder” region in Morocco was performed utilizing the k ₀-standardization method. Sample irradiation has been done by the 250 kW Triga Mark II reactor at Jozef Stefan Institute in Slovenia. Due to its accuracy, sensitivity and specificity, the k ₀-standardization method is the most suitable method for non-destructive multielement analysis mainly for trace elements in rocks. It requires an accurate knowledge of the parameters of the irradiation facilities and other instrumentation parameters. It is an absolute standardization method, where the absolute nuclear data are replaced by a nuclear constant, the k ₀-factor, determined experimentally with high accuracy. More than 40 elements were determined using about 30-second short and about 7-hour long irradiations. Gamma-rays emitted from the irradiated samples have been determined by a high purity germanium detector. Accuracy was assessed using the standard reference material AGV-1. This was less than 1% for major elements and about 5% for traces. This revised version was published online in July 2006 with corrections to the Cover Date.     

Instrumental neutron activation analysis of rock samples from Ugep area of Cross River State,Nigeria

The theory and analytical procedures in Instrumental Neutron Activation Analysis (INAA) are discussed. Application of the method to the determination of sixteen trace elements: Na, K, Mn, Sm, La, Fe, Th, Sc, Co, Ba, Rb, Br, Sb, Cs and Ta in some rock samples from Ugep in the Lower Benue Region of Nigeria, is described. The high radioactivity observed in some of the samples analyzed has been associated with the higher-than-normal concentrations of Th and K in the samples. Also, Ba and Fe concentrations in some of the samples were found to be anomalous when compared with average expected values in normal sedimentary rocks.     

The capability of neutron activation for trace element analysis in sea water and sediment samples of the Northern Adriatic Sea

In a framework of a more intensive study of the oceanographic phenomenology of the Northern Adriatic Sea, recently undertaken by the O. G. S. of Trieste, the present paper provides some insight into the determination of trace elements in sea water and bottom sediment matrices. Sampling procedure using continuous pumping and filtering and neutron activation analytical techniques are presented and the obtained results briefly discussed. Accounting for the physiography of the basin, for the oceanographic processes and for the different freshwater input, several samples were collected of filtered water in order to set up their properties. Results were obtained throughout the settlement only for long-lived radionuclides based on routine neutron activation: Cr, Ag, Co, Cs, Rb, Sb, Sc, Sr, Zn, U. For each of them, the concentration range was determined and discussed. Results indicate that the Cs, Rb, Sr and U concentration range is readily comparable with that assessed at open seas. On the contrary, for the other elements such as Cr, Ag, Co, Sc, Sb and Zn concentrations are noticeably higher than those found at open seas, mainly as far as samples collected near the sea bottom are concerned. The concentration increase is surely related to the burden of pollutants suffered by rivers. Moreover, the positive concentration gradient experienced toward the bottom, is fully in agreement with the estuarine character of the investigated area and in accordance with the strong decomposition of organic matter taking place in the bottom layer of the basin. Finally, the complexity of the sedimentary pattern in the Northern Adriatic renders it difficult to properly define the element concentration in bottom sediment. Only four samples were chosen as representative of the different sediments and analysed. Long-lived elements obtained are: Ce, Co, Cs, Cr, Rb, Sc, Tb, Yb. Their concentration was found to be related to the geochemical features of the activated matrix.     

Instrumental neutron activation analysis of urinary calculi

Five kinds of urinary stones from 42 patients have been determined for a total of 19 elements by instrumental neutron activation analysis. Of these elements, Ca, Mg, Sr, Na, and Cl are found to be present in the core of all kinds of stones. The differences in elemental composition among the different kinds of stones as well as across the layers of stone are statistically evaluated.     

Instrumental neutron activation analysis of Obsidian rock

An instrumental neutron activation analysis technique has been developed for the simultaneous determination of up to 30 elements including major, minor and trace elements in Obsidian Rock (a proposed NBS-SRM-278). INAA method involves both short and long irradiations followed by gamma-ray activity measurement with a Ge(Li) detector. The accuracy of the procedure has been checked by analyzing IAEA Reference Materials.     

Instrumental neutron activation analysis of brewer's yeast

Instrumental neutron activation was used for the determination of 23 trace and minor elements in 4 different samples of brewer's yeast. Detection limits for these elements vary from 2 ppb to 100 ppm. The following average concentrations were found (ppm, dry weight): Al 597, Br 0.36, Cl 1473, Co 0.21, Cu 19, Fe 285, K 16 400, Mg 1355, Mn 8.4, Na 2330, Rb 19, Sb 0.053, Se 1.2, V 2.2 and Zn 80. NBS standard 1569 was also analyzed and the following concentrations (in ppm) were measured: Al 2300, Br 0.65, Ce 0.23, Cl 460, Co 0.26, Cr 2.12, Cu 11, Fe 707, Gd 7.1, Hf 0.13, K 15 500, Mg 1780, Mn 7, Na 510, Rb 16, Sb 0.075, Sc 0.18, Se 0.92, Th 3.7, Ti 38, U 0.49, V 4.1 and Zn 70.     

Instrumental neutron activation analysis of blood serum

Instrumental neutron activation analysis has been used to determine 15 trace elements in twelve blood serum samples taken from healthy students at Bilkent University in Ankara. The method allowed the determination of Sc, Cr, Mn, Fe, Co, Zn, Se, Rb, Cs, Ce, Eu, Tb, Hf, Ta and Hg, which occur at the g.ml^–1 to ng.ml^–1 levels. There are no values reported for Tb, Hf, Ce, Eu and Ta before. The other results are compared with the values reported in the literature. Most are in the range of the reported values except for Fe, Zn, Se and Cs.     

Instrumental neutron activation analysis of gunpowder residues

A procedure has been developed for the detection of gunpowder residues deposited on the hand of a person firing a gun. The method is based on neutron activation analysis of the antimony level on the surface of the hand. The surface materials are removed by a film made by spraying a 4% solution of cellulose acetate in acetone, which sets to form a thin film that can readily be stripped off. This technique was found to be preferable to the paraffin-lift technique which is in common use. Following neutron activation of the film in a nuclear reactor, antimony is assayed by high-resolution Ge(Li) spectrometry without prior chemical processing. The sensitivity of the method is about 5·10⁻⁹ g Sb, with a precision of about ±10% at a neutron flux of 5·10¹³ n·cm⁻²·sec⁻¹. Analysis of twenty samples taken from the hands of persons who had fired a pistol gave Sb levels of 0.4±0.2 μg, compared with 0.024±0.013 μg found on the hands of persons who had not fired a revolver. The possible extension of the present technique to include the determination of additional elements is discussed. Project carried out with the support of the Office of the Chief Scientist to the Ministry of Defense and with the collaboration of the Israel Police.