Determination of gold by neutron activation analysis in some selected rocks and plants and its bearing on the genesis of auriferous quartz veins in Singhbhum district,Bihar, Eastern India

Present investigation deals with neutron activation analysis of gold in some varieties of geological samples related to auriferous quartz veins. A few plant specimens of the area were also analyzed. The gold contents in the rock samples as determined by the destructive way of analysis vary in the range 10⁻⁵ to 10⁻⁷%. In case of plant samples, however, the non-destructive method of analysis of the plant ashes was followed and the concentration of gold was found to be of the order of 10⁻⁵%. In plants, besides gold, some associated elements, such as La, Ce, Sm, Lu, Zr, Hf, Se, W, As and Sb were also identified.     

Radioactivation analysis of aluminium,vanadium, copper,molybdenum, zinc and uranium in natural water samples using organic coprecipitants

A method is described for the determination of trace metal ions, V, Al, Cu, Mo Zn, and U, in natural water samples by neutron activation analysis, using organic coprecipitation as a preconcentration method. The preconcentration of trace elements was accomplished by converting the dissolved trace metal ions into the oxine chelates atpH 5.2 and extraction of the chelates witho-phenylphenol which is a liquid above 56 °C and solidifies at room temperature. After cooling the extraction system, the fine particles of the organic phase were collected on a millipore filter and the precipitate was air-dried in a clean environment. The solid extract was wrapped up in a sheet of clean polyethylene and subjected to neutron irradiation in a reactor for less than 10 min at a thermal flux of 2·10¹³ n·cm⁻²·sec⁻¹. γ-Ray spectrometry by a coaxial Ge(Li) detector connected to a 1024-channel PHA was performed on the irradiated sample without further chemical separation, and thus the ppb level concentration of the elements in natural water samples could be determined. The fundamental study of the collection of the trace elements is also described.     

Investigation of the interaction of Greek dolomitic marble with metal aqueous solutions using rutherford backscattering and X-ray photoelectron spectroscopy

To enhance the applicability of the nuclear analytical technique in the field of industry and the environment, the inorganic elemental content of the bottom ash from a municipal solid waste incinerator was determined by instrumental neutron activation analysis. Bottom ash samples were monthly collected from an incinerator located at a metropolitan city in Korea, strained through a 5 mm sieve, dried by an oven and pulverized by an agate mortar. The samples were irradiated at the NAA #1 irradiation hole (thermal neutron flux: 2.92·10¹³ n·cm⁻²·s⁻¹) in the HANARO research reactor of the Korea Atomic Energy Research Institute and the irradiated samples were measured by a HP Ge gamma-ray spectrometer. Thirty-three elements including As, Cr, Cu, Fe, Mn, Sb and Zn were analyzed by an absolute method. The quality control was conducted by a simultaneous analysis with NIST standard reference materials. The average concentrations of the major elements such as Ca, Fe, Al, Na, Mg, K and Ti measured in the sample were 19.9%, 4.85%, 3.79%, 2.11%, 1.84%, 1.22% and 1.02%, respectively. In addition, the concentrations of the hazardous metals like Zn, Cu, Cr, Sb and As were 0.77%, 0.31%, 729 mg·kg⁻¹, 116 mg·kg⁻¹ and 22.2 mg·kg⁻¹, respectively.     

Gamma ray spectra and sensitivities for 14 MeV neutron activation analysis

The purpose of this study was to define experimentally the sensitivity of determination for 63 different elements by 14 MeV neutron activation, with a 150 kV Cockroft-Walton accelerator at a neutron flux of 2·10⁸ n·cm⁻²·sec⁻¹ on the sample. The obtained gamma ray spectra are given, and the origin of the photopeaks observed are explained. A maximum irradiation time of five minutes was used as a convenient experimental limit to obtain the maximum sensitivity, considering, however, that the tritium target life is limited, and that the time to perform an analysis has to be reasonable. The practical use of 14 MeV neutron activation analysis is demonstrated by the detection limits obtained.     

Experimental sensitivities for 3 MeV neutron activation analysis

The experimental sensitivity for 72 different elements using 3 MeV neutron activation has been investigated. Using a 200 kV Cockcroft-Walton neutron generator with a 3 MeV neutron flux of about 1.5·10⁶n·cm⁻²·sec⁻¹, γ-ray spectra of 51 elements were obtained with a sufficient number of photopeak counts for sensitivity calculations using a photopeak integration method. A useful table summarizing the sensitivity results is given. That 3 MeV neutron activation analysis is practical, is demonstrated by the experimental sensitivities obtained. Guest worker from the Institute of Nuclear Techniques, Academy of Mining and Metallurgy, Krakow, Poland, at the National Bureau of Standards, 1968–1969.     

Rare-earth elemental analysis of banded iron-formations by instrumental neutron activation analysis

Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux of 5.1·10¹⁶ m⁻²·s⁻¹, 1.0·10¹⁵ m⁻²·s⁻¹ and 3.7·10¹⁵ m⁻²s⁻¹, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector. Ten rare-earth elements, such as La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu, have been qualitatively identified and quantitatively estimated in these samples. The present investigation is an example of employing a pre-concentration method for high iron-containing ores prior to neutron activation analysis.     

Multi-element analysis of biological samples after intense neutron irradiation an fast chemical separation

For the simultaneous determination of many elements in small biological samples, a multi-element analysis has been developed using neutron activation. After a 24-hr irradiation in a neutron flux of 2.5·10¹⁴ n·cm⁻²·sec⁻¹ and after immediate chemical separation without cooling, it was possible to analyse 24 elements in bovine liver (NBS-SRM 1577). The separation apparatus, set up in a shielded cell can work four samples simultaneously, and its operation is fast enough to allow the detection of radioisotopes with a half-life of about 2 hrs (¹⁶⁵Dy,^57mSr,⁵⁶Mn). Amounts lower than 10⁻³ μg of Dy, Eu, Pr, Sm and Yb were determined.     

The determination of bromine and iodine in environmental water samples by thermal neutron activation and isotope exchange

A routine-method for the determination of bromine and iodine in environmental water by neutron activation is presented. The elements are isolated by isotope exchange between the irradiated sample and a solution of Br₂ or I₂ CCl₄. The method is not sensitive to the chemical species in which the halogen is present. The lower limit of the determination is 1.0 μg Br·1⁻¹ and 0.1 μgI·1⁻¹.     

Gallium determination in biological samples

A sensitive, simple and time-saving method has been developed for the neutron activation analysis of gallium at concentrations around 10⁻⁴ ppm in biological tissues. After a 24-hour irradiation in a thermal neutron flux of 2.8·10¹³ n·cm⁻²·s⁻¹ and a purification by ion-exchange chromatography to eliminate troublesome elements such as sodium, iron and copper, the⁷²Ga activity is measured with enough accuracy for the method to be applicable in animal physiology and clinical toxicology.     

Detection limits of Au using fast and thermal neutron activation analyses

The applicability of fast and thermal neutron activation analyses for the determination of gold in rock samples has been studied. Using a Ge/Li/ detector limit of 0.45 mg g⁻¹ was obtained for a fast neutron flux of 8.10⁷ n cm⁻².s⁻¹. With a thermal neutron flux of 6.10⁵ n cm⁻².s⁻¹ and the same detector a value of 35 μg g⁻¹ was obtained. Using a NaI/Tl/ crystal a sensitivity of 14 μg g⁻¹ was attained at the same thermal flux. This work was supported in part by the Hungarian Academy of Sciences.     

Concentrations of trace and major elements in Mission–Progresso (Texas) soils

Neutron Activation Analysis (NAA) was applied to determine trace and major elements in Mission–Progresso (Texas) soils. The Rio Grande river runs along the USA—Mexico border. The soil samples were collected at Mission and Progresso areas of the Rio Grande riverbank in the USA side. Soils were analyzed for the presence of toxic effluents due to human activities that might affect agricultural products and health because one of the possible paths of intoxication is the agricultural product consumption. Dried, sieved, and blended soil samples (~1.5 g) were irradiated at the UT Austin TRIGA reactor at a thermal neutron flux of 1 × 10¹² n cm⁻²s⁻¹ and epithermal neutron flux of 1 × 10¹¹ n cm⁻²s⁻¹. Different irradiations, decay, and counting times were combined to determine concentration and detection limits of 21 elements which represent four areas in Mission–Progresso (Texas) with the aim to achieve a consistent characterization. NIST certified reference materials were used in relative analysis and also to determine the accuracy and reproducibility values. The neutron flux was monitored using sulfur flux monitor wires. Normal and Compton suppression gamma ray spectrometers were used to detect different gamma ray energy peaks and this Compton system greatly reduces the background. Concentrations are evaluated in per cent and parts per million and errors are within acceptable levels and these values are compared with values reported in literatures from other countries. The results do not show significant contaminations neither from the Rio Grande river nor from nearby industries.     

Characterization of trace elements in medicinal herbs by instrumental neutron activation analysis

Medicinal herbs are often used as alternative medicines for healing and controlling some diseases in the world. This study focuses on the content of heavy and trace elements of some widely consumed herbs in Libya. Nine most popular herbs were analyzed by k ₀-instrumental neutron activation analysis. All the samples, SRM and flux monitors were irradiated for 7 and 10 hours under thermal neutron flux of 1.3·10¹³ cm⁻²·s⁻¹ at Tajoura nuclear reactor. In total, 33 elements were analyzed in different herbs. The variations in the concentration of the elements are attributed to soil composition and the climate in which the plant grows. The study showed that the toxic elements found in the samples were below the levels prescribed by health regulations. The precision and the accuracy of the results were evaluated by analyzing the reference materials Pine Needles SRM 1575 and Citrus Leaves SRM1572.     

Neutron activation analysis of rare earth impurities in metallic uranium

A method with a sensitivity of 2·10⁻⁷ to 1·10⁻¹⁰% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)₃, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.     

Reagent-loaded and unloaded polyurethane foam as preconcentration matrix in neutron activation analysis

Loaded and unloaded polyurethane foams were examined as a preconcentration matrix in combination with neutron activation analysis. The structure of the foamed polymer is not damaged by short irradiation periods. However the foam skeleton degraded after irradiations for one hour or longer in a neutron flux of 3·10¹³ n ·cm⁻²·s⁻¹. The presence of tin as a major impurity in the polyether-type foam has been detected. This may affect the sensitivity of determination of the relatively short lived isotopes of the elements collected on the foam. On the other hand the polyester-type foam was found to contain only very low amounts of tin. Antimony, indium, gold and mercury collected on the foams were determined with reasonable accuracy.     

The search for internal isotopic tracers in metallurgical materials

In a search for internal isotopic tracers in metallurgical materials a group of elements has been chosen which can be determined by the neutron activation method with the higher sensitivity. A method has been developed for the determination of W, As, Au, La, In, Sc, Re and Ir in metallurgical materials. The separation of the elements was carried out using extraction and precipitation. The determination of the elements was carried out in samples of chamotte brick and washed ores. The limits of the determination of the elements are of the order of 10⁻¹¹ g for Au, 10⁻¹⁰ g for In and La and 10⁻⁹ g for As, W, Sc, Re and Ir. The large scatter of the results indicates the inhomogeneity of the materials analyzed.     

Analytical use of neutron-capture gamma-rays

Certain elements which are not possible to detect with conventional neutron activation analysis can be measured using thermal neutron-capture gamma-ray analysis. The use of a curved neutron guide at the High Flux Reactor, Grenoble, with a thermal neutron flux of 1.5·10¹⁰n·cm⁻²·sec⁻¹ and the advantage of a low-background counting system (Ge(Li) detector) far from the reactor core are described. Experimental detection limits of a number of elements are given for the low-energy and the high-energy regions. Some applications of the capture gamma-ray method in the whole energy range are studied and are briefly discussed.     

U determination in environmental samples by delayed neutron activation analysis in Korea

A delayed neutron counting system has been implemented at the HANARO research reactor in 2007. Thermal neutron flux measured at the NAA #2 irradiation hole coupled to the delayed counting system, was higher than 3 × 10¹³ n cm⁻² s⁻¹. The delayed neutron counting system is composed of 18 ³He detectors which are divided into three groups with six detectors and the collected signals of each group are processed to a digital signal. The count numbers were measured with the uranium mass by using NIST SRMs under fixed analytical condition and their correlation could be determined. Finally, delayed neutron activation analysis has been carried out for the determination of uranium mass fraction in the collected environmental samples.     

Fast-neutron activation analysis with short-lived nuclides

At the GKSS Research Center Geesthacht, a new 14 MeV activation facility—a 5·10¹² n/s neutron generator combined with a fast rabbit system (KORONA)—is being installed. Homogeneous neutron flux at a level of 5·10¹⁰ n·cm⁻²·s⁻¹ and sample transfer times of 140 ms to a 16m distant detector station are characteristic features of the facility described in the paper. With special consideration of short-lived nuclides and including cyclic activation, the analytical prospects with the intense neutron source are discussed, and sensitivities for 78 elements are presented.     

Neutron activation analysis of uranium in human bone,drinking water and daily diet

Uranium in human bone, drinking water and daily diet has been determined by neutron activation analysis using the²³⁸U(n, γ)²³⁹U reaction. An improved scheme for the separation of the²³⁹U is proposed; with this scheme, after neutron irradiation in a 100 kW TRIGA reactor, a uranium content as low as 5·10⁻¹¹ g can be determined reliably, rapidly and easily. A wide range of uranium concentrations, from about 0.1 ppb up to about 10 ppb has been found in the bones of normal Japanese. Water from several Japanese city water services, and the daily diet taken in two Japanese cities, have been found to contain an average 9·10⁻⁹ g/l and 1.5 μg per person-day uranium, respectively.