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.     

Trace determination of iron on a silicon wafer surface by silicon direct bonding and neutron activation analysis

In order to determine iron on silicon wafer surface at a level of 10¹⁴ atoms·m^–2 the efficiency of a well-type Ge detector for⁵⁹Fe -ray emissions was measured and a low temperature silicon direct bonding technique was developed. With silicon direct bonding at a temperature of 350 to 650°C iron remains near the interface of the bound silicon. The iron contamination of the interface escaped from the interface can be ignored with this technique. The value of iron obtained was (2.7 to 5.9)·10¹⁴ atoms · m^–2 in the surface on silicon wafers.     

Method for determination of silicon in plant materials by neutron activation analysis

Silicon has been found to be an essential element for the growth and development of many ecomomically important plants such as sugarcane, rice, oats, and wheat. A method is described for the quantitative determination of silicon in plant samples. Measurements were made with two Ge(Li) detectors matched with a multiplexing unit to provide a single amplified signal to a computerized analyzer system. For those materials containing greater than 0.5 weight percent silicon, the reaction²⁹Si(n, p)²⁹Al (1273 keV) provides a direct measurement of the quantity of silicon provided the irradiation is done in a special boron nitride capsule to reduce interferences from thermal neutron reactions and a correction is made for the single escape line from²⁸Al (1268 keV). For lesser quantities of silicon, a technique which utilizes the fast neutron reaction²⁸Si(n, p)²⁸Al is preferred. Corrections for the interference produced by the presence of phosphorus³¹P(n, α)²⁸Al are made by determining the phosphorus content following the instrumental analysis using a unique application of neutron activation analysis, i. e., measurement of tungsten in tungstomolybdophosphoric acid produced when molybdate and tungstate ions are added to dissolved samples of the plant material containing phosphorus. Aluminum, which may also produce an interference by thermal neutron reaction²⁷Al(n, γ)²⁸Al, is determined directly from the original activation data after subtracting out the effect of the phosphorus. Thus, three irradiations in the pneumatic sample irradiator are necessary; one short irradiation (1 min) without thermal neutron shielding, a longer irradiation (6 min) in the boron capsule, and a final irradiation of the tungstomolybdophosphoric acid provide all data required to accurately determine silicon in plant materials. A computer program has been developed that provides rapid reduction of the data in final report format. Elements such as sodium, chlorine, calcium, manganese, potassium, and magnesium extrinsic to the analysis for silicon are also determined by this method. The method has been tested on a large number of samples and reliable results are obtained with less than 0.2 g of sample. This work was supported by Grant 533 from the Michigan Memorial—Phoenix Project.     

Activation analysis of selenium in organic samples,through selenium-77m,on a pre-separation basis

A method is described to separate trace amounts of selenium in organic samples without using a carrier, based on the adsorption on active carbon filters of the complex formed with APDC at pH 1.5. The separation is made prior to the neutron irradiation and the correction for selenium in the reagents performed by the irradiation of a blank. The method has been successfully used in fodder samples as well as some other organic reference materials, using a fast pneumatic transfersystem, which takes the samples from the irradiation position to the counting position in 3s, with the only limitation of the thermal neutron flux available, 4.7·10¹¹ cm^–2·s^–1. Detection limits of 0.1 g are obtained under these experimental conditions.     

Study on air pollution monitoring in Korea using instrumental neutron activation analysis

Trace elements in airborne particulate matter collected monthly at suburban and rural areas in Korea were analyzed by instrumental neutron activation analysis (INAA). Neutron irradiation of the samples was done at the irradiation hole (neutron flux 1·10¹³ n·cm^–2·s^–1) of the TRIGA Mark-III Research Reactor in the Korea Atomic Energy Research Institute. For the verification of the analytical technique, two reference materials, NIST SRM-1648 and NIES CRM-8, were chosen for analysis. The accuracy and precision of the determinations of the 40 elements were compared with the reference values. We used this method (1) to analyze 30 trace elements in airborne particulate matter collected monthly with the high volume air sampler (PM-10) at two different locations and (2) to confirm the possibility of using this method as a routine monitoring tool to find out environmental pollution sources.     

In vivo activation analysis of organ cadmium using the Tsing Hua Mobile Educational Reactor

This work describes a nuclear facility forin vivo prompt gamma activation analysis (IVPGAA) using a moderated neutron beam from a 0.1 W Tsing-Hua Mobile Educational Reactor (THMER). The IVPGAA measurement is a new technique for toxic cadmium determination in organs, which can efficiently be used in clinical diagnosis. The low-power nuclear reactor provides a total neutron flux of 3.3·10⁴ n·cm^–2·s^–1 on the surface of the central vertical neutron beam tube to which a liquid phantom is positioned. The capability of such partial-body irradiation facility is demonstrated. The detection limit of cadmium in the left kidney for a skin dose equivalent of 1.66 mSv (166 mrem) was 1.34 mg in a 500-s irradiation/counting period, and the sensitivity in the left kidney was 103 counts mg^–1·mSv^–1. The performance of IVPGAA system using the THMER nuclear facility therefore has the advantages of mobility and feasibility with high sensitivity under low neutron and gamma doses.     

Neutron activation analysis of low level lithium in water samples

For determining low level lithium concentrations in water, a neutron activation method based on the measurement of tritium radioactivity produced by⁶Li(n,)³H reaction has been developed. This method is specific and free from interference by other chemical elements. Using a low background liquid scintillation counter for tritium measurement, the detection limit is approximately 0.3 ppm during irradiation at a thermal neutron flux density of 1.1·10⁷n·cm^–2·s^–1 for 6 hours by a small nuclear reactor and liquid scintillation counting for 2000 minutes     

Reactor neutron activation analysis by a triple comparator method

The single comparator method has been extended to a triple comparator method, using⁶⁰Co,^114m In and¹⁹⁸Au. In this technique, thek-ratios of the elements to be analyzed, now determined against the three comparators, are corrected for each new ratio of thermal to epithermal reactor neutron flux. These flux ratios are calculated from the absolute activities of the three comparators. The thermal neutron activation cross-section and the resonance integral for the reaction¹¹³In(n,γ)^114m In have been determined.     

Fast neutron activation analysis of silicon in aluminum alloys

The silicon content in an aluminum-silicon alloy was measured by nondestructive fast neutron activation analysis with fission spectrum neutrons. A boron nitride irradiation container reduced the flux of thermal and epithermal neutrons at the sample position, enhancing the²⁹Si (n, p)²⁹Al reaction. A detection limit of 0.4% silicon in a 0.5 g alloy sample was obtained.     

Simultaneous determination of silicon and aluminium in ferrosilicon by instrumental neutron activation analysis with the aid of an Ac-Be isotopic neutron source

A method has been developed for the accurate determination of silicon and aluminium by instrumental neutron activation analysis with the aid of an²²⁷Ac-Be isotopic neutron source. The samples are pellets made of 4.6 g of ferrosilicon and 0.9 g of a pelletizing agent. Each pellet is irradiated twice at two different fast-to-thermal neutron flux ratios. Each irradiation is followed by two integral mode countings. This allows correction for manganese activities and calculation of the fraction of the aluminium activity induced in silicon and aluminium. The method has been tested with laboratory-prepared synthetic samples as well as commercially certified ferrosilicon. For ferrosilicon containing 75% Si, a relative precision of 0.7% for the results of the silicon concentration has been obtained. For aluminium the relative precision varied from 2 to 7% for concentrations of 3.5 to 1.5%.     

Non-destructive determination of silicon in aluminium-silicon alloys by neutron activation analysis with a 227Ac-Be isotope neutron source

A method has been developed for the accurate determination of silicon in binary Al-Si alloys by instrumental neutron activation analysis with the aid of an ²²⁷Ac-Be isotope neutron source. Discs, weighing ca. 4 g, are irradiated at the maximum of the fast flux gradient in a rabbit lined internally with two layers of cadmium foil. Each irradiation is followed by an integral mode counting with discriminator baseline setting at 1400 keV. Standards consist of discs from high purity semiconductor silicon and aluminium (99.99%) metal. An iterative calculation procedure yields results with a relative precision from 0.6 to 8.1% for silicon contents between 13.5 and 0.5%. Triplicate analysis requires 21 min.     

Characterization of solar grade silicon by Neutron Activation Analysis

An analytical method using neutron activation was developed in order to orientate and check different silicon elaboration processes either as solid ingots or ribbon shaped. This method without chemical separation after irradiation implies the use of a high efficiency semiconductor detector. A particular attention was paid to different causes of error and to the detection limits really obtained. These limits range from 10⁹ to 10¹⁵ at.cm^–3 for about 30 elements systematically locked for after a 72-h irradiation.     

A search for losses of chemical elements during freeze-drying of biological materials

Possible losses of seven chemical elements were investigated in biological tissues during freeze-drying in vacuum. Thyroid glands were taken during post-mortem examination of 23 people died of different diseases. Instrumental neutron activation analysis (INAA) was used to estimate contents of Br, Ca, Cl, I, K, Mg, and Na. The nuclear reator vertical channel with flux density of 1.2·10¹³n·cm^–2·s^–1 was used for neutron irradiation. The analysis was carried out using short-lived radionuclides induced in samples after neutron irradiation. Then thyroids were freeze-dried at below 0 °C in vaccum up to the constant mass (lyophilisation) and then homogenized. Samples of lyophilised and homogenized tissues were again studied by INAA. The lack of difference between the results of the analysis before and after lyophilisation is an evedence of no loss of Br, Ca, Cl, I, K, Mg and Na during freeze-drying of biotissues in vaccum.     

Instrumental neutron activation analysis of semiconductor grade silicon

The single comparator method in neutron activation analysis has been applied to the investigation of the purity of silicon single-crystals of different origins. The following impurities were determined: Au, Sb, Co, Cu and Na. Studies were also carried out on the surface contamination of silicon samples introduced through steps of sample preparation and irradiation. Up to nineteen elements on the surface of samples were analysed and found to be easily reduced to low levels or detection limits by washing and etching.     

Anion exchange behaviour of the transplutonium elements in hydrochloric acid-alcohol media at elevated temperature

The use of instrumental neutron activation analysis (INAA) in determining selected elements in biological materials has been reported by numerous authors. Some of these have detailed the use of INAA to determine an elemental analysis in tobaccos of various geographical origins. This paper describes the first use of INAA to measure the distribution of selected inorganic elements within the tobacco leaf at a single plant stalk position for one tobacco curing routine. Three replicate plots of a common bright tobacco cultivar were grown under normal cultural conditions characteristic for the bright variety. The tobacco leaves were sampled at selected positions in the leaf. The brigh tobacco was cured in a conventional flue-curing barn using standard practices. Immediately after collection, each individual sample was freeze-dried, crushed and sampled. The leaf midrib samples were prepared using a similar procedure. A subsample of about 100 mg was taken from each sample, sealed in a polyethylene bag, irradiated in a thermal neutron flux of 2×10¹⁷ n·m^–2·s^–1 in a pneumatic rabbit system, and subsequently counted to obtain the reported data. A standard reference material was used as a comparator to yield relative elemental concentrations for Ca, Mg, Mn, Na, K, Cl and Br. The data show that chlorine, potassium, sodium and calcium have definite concentration trends within the tobacco leaf. The data also show that some elements, e.g. Mn, were more uniformly distributed throughout the leaf.     

Intercomparison and determination of environmental standard samples by instrumental neutron activation analysis

To identify and improve the analytical technique for air pollution research, four kinds of environmental standard samples, i.e., airbome particulate matter, coal flyash, soil and pine needle supplied from the NIST and the IAEA were analyzed using thermal and epithermal neutron activation techniques. Sample irradiation was done at the irradiation facilities (neutron flux, 1 · 10¹³ n·cm^–2·s^–1) of the TRIGA MARK-III Research Reactor in the Korea Atomic Energy Research Institute. The accuracy and precision for the analysis of 40 trace and toxic elements in the samples were compared with the certified and reported values, respectively. In the analytical results of all standard reference materials, the relative standard deviation were within the 15% except for 11 elements and the relative error were agreed within the 10–20% except for 13 elements. The benefit of epithermal activation was investigated and the optimum analytical condition is reported.     

Neutron activation determination of oxygen in ceramic materials on the basis of yttrium,barium and copper

A procedure of determining oxygen in superconducting materials on the basis of yttrium, barium and copper oxides with the application of 14 MeV-neutron activation has been developed. The method is based on determining the relation between oxygen and yttrium in the compounds investigated. Quantitative evaluation of this relation is performed with the aid of a comparator and two-component monitor. In order to minimize systematic errors, expressions accounting for spectrometer dead time under conditions of varying component activity are proposed. The procedure ensures determination of the relation between oxygen and yttrium with a relative error of 0.4%(10 parallel measurements) with NAA using a neutron generator with a neutron yield of (1–3)·10¹⁰ n·s^–1.     

Instrumental neutron activation analysis of Al,V and Ti employing252Cf as a thermal neutron source

A rapid method for the determination of Al, V and Ti has been developed and is used for the analysis of these elements in different ores and alloys. An isotopic neutron source²⁵²Cf having a thermal neutron flux of the order of 8.5×10⁷ n·cm^–2 sec^–1 has been used for thermal neutron bombardment. Activity measurements were performed on a HPGe detector coupled to a PC based MCA unit. Depending on the half-life of the (n, ) product, different irradiation and cooling times were employed and thus the elements of interest were analyzed sequentially.     

Characteristics and behavior of a99Mo/99mTc generator using irradiated titanium molybdate as column matrix

A⁹⁹Mo/^99mTc generator, system was made with a performed titanium molybdate gel. The irradiation was carried out at a medium neutron flux of 1.5×10¹³ n cm^–2·s^–1. The irradiated matrix was loaded on top of a column composed of hydrous zirconium oxide alumina. The elution efficiency and the amount of total technetium per mCi^99mTc in the generator eluents have been determined. Molybdenum breakthrough has also been determined and compared with literature values. The influence of the particle size, water content, neutron flux and molybdenum content on the total^99mTc-activity has been investigated.     

Test-fitting on adsorption isotherms of organic pollutants from waste waters on activated carbon

An alternative method of approach has been developed for the measurement of thermal neutron flux. The method depends only on the activity of the bare foil if the cadmium ratio at the irradiation position is known. The method has been tested on the GHARR-1 facility at the Ghana Atomic Energy Commission using gold and indium foils for the measurement of the thermal neutron flux in the flux range of 10¹⁰–10¹² n·cm⁻²·s⁻¹ and the results compare very well with those obtained using the conventional method (cadmium separation method).