Multielement analysis of Chinese Biological Standard Reference Material by monostandard instrumental neutron activation analysis

A procedure for monostandard INAA of 21 elements (Hg, As, Br, Cr, Sb, Se, Ba, Zn, Ca, Ce, Co, Cs, Eu, Fe, Hf, K, La, Rb, Sc, Sr, Ta) in Chinese Biological Standard Reference Material (peach leaves) is described. The accuracy of the procedure was checked by analyzing the U.S. NBS Standard Reference Materials SRM-1571 and SRM-1632a.     

Homogeneity test of Chinese Biological Standard Reference Material by means of instrumental neutron activation analysis

A homogeneity test of 14 elements (Al, Cl, Mn, K, Ca, Ce, Th, Hf, Cs, Sc, Fe, Zn, Co and Eu) was made in Chinese Biological Standard Reference Material (peach leaves) by means of INAA. The procedures are described and the results are presented and discussed.     

Routine multielement instrumental neutron activation analysis of silicate rocks using short-lived radionuclides

By means of thermal neutron activation and countings on the small planar and large coaxial Ge(Li) detector, 13 elements are determined in various silicate rocks, using short-lived radionuclides with half-lives from 2 min to 15 h. A method of routine analysis with simple dead-time and pile-up correction is described and tested with the standard rocks AGV-1 and G-2.     

Errors in instrumental neutron activation analysis based on short-lived radionuclides

Accuracy and precision of instrumental neutron activation analysis, based on short-lived radionuclides, are considered. Equations are derived for both quantitives as a function of concentration and features of the γ-ray spectrum. The determination of vanadium by way of⁵²V(T=3.75 min) is used as an example.     

Fast neutron activation analysis using short-lived radionuclides

Fast neutron activation analysis experiments were performed to investigate the analytical possibilities and prospective utilization of short-lived activation products. A rapid pneumatic transfer system for use with neutron generators has been installed and applied for detecting radionuclides with a half-life from 300 ms to 20 s. The transport time for samples of total mass of 1–4 g is between 130 and 160 ms for pressurized air of 0.1–0.4 MPa. The reproducibility of transport times is less than 2%. The employed method of correcting time-dependent counting losses is based on the virtual pulse generator principle. The measuring equipment consists of CAMAC modules and a special gating circuit. Typical time distributions of counting losses are presented. The same 14 elements were studied by the conventional activation method (single irradiation and single counting) by both a typical pneumatic transport system (run time 3 s) and the fast pneumatic transport facility. Furthermore, the influence of the cyclic activation technique on the elemental sensitivities was investigated.     

Beta spectroscopy of short-lived radionuclides using in-cocktail neutron activation

Low-flux, in-cocktail neutron activation analysis was used to quantify atmospheric tracer aerosols. Liquid scintillation was necessary to reduce the experimental uncertainty due to low sample activity. Activation of the tracers was performed in-cocktail since the short half lives of the nuclides did not allow time for sample preparation. Most of the tested cocktails proved inadequate for such analysis because of activation of their components. Neutron and gamma induced luminescence, and neutron generated bubbles in suspensions introduced further difficulties. Only a few cocktails showed activity levels after irradiation comparable to background. This method allowed substantial cost reduction by eliminating the need for irradiation in a research reactor.     

Recent instrumental neutron activation analysis studies utilizing very short-lived activities

The advantages and disadvantages of utilizing very short-lived induced activities (half lives in the range of 0.3 sec to 60 sec) in neutron activation analysis are reviewed. Results obtained with the recently described fast-transfer system and deadtime correction system are presented. They include results for 12 elements (F, S, Cl, Sc, Ge, Se, Br, Y, Zr, Ba, W, Pb), in both steady-state and high-intensity pulse irradiations, in both unlined and cadmium-lined irradiation positions. The half lives of the 12 species studied range from 0.3 sec to 18.7 sec. Some further aspects of the deadtime correction system are discussed.     

Multielement analysis of Chinese Environmental Reference Materials by instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) has been applied for the simultaneous determination of up to 33 elements including major, minor and trace elements in the environmental reference materials soil and coal fly ash from China. The procedure involves both short and long irradiations followed by the measurement of the gamma spectra with a Ge(Li) detector. The analytical results are presented and discussed.     

14 MeV neutron activation analysis using short-lived products

Cyclic activation using pneumatic shuttling system and switch off and on the neutron source and detector are described in order to eliminate some uncertainties by the provision of more accurate timing, the measurement of the effective activating neutron flux and the correction for the detection system dead time.     

A software counting loss correction method for neutron activation analysis with short-lived radionuclides

A method has been developed for the correction of counting losses in NAA for the case of a mixture of short-lived radionuclides. It is applicable to systems with Ge detectors and Wilkinson or successive approximation ADC's and will correct losses from pulse pileup and ADC dead time up to 90%. The losses are modeled as a constant plus time-dependent terms expressed as a fourth order polynomial function of the count rates of the short-lived radionuclides. The correction factors are calculated iteratively using the peak areas of the short-lived radionuclides in the spectrum and the average losses as given by the difference between the live time and true time clocks of the MCA. To calibrate the system a measurement is performed for each short-lived nuclide. In a test where the dead time varied from 70% at the start of the measurement to 13% at the end, the measured activities were corrected with an accuracy of 1%.     

Instrumental neutron activation analysis technique using subsecond radionuclides

The fast irradiation facility Mach-1 installed at the Danish DR 3 reactor has been used in boron determinations by means of Instrumental Neutron Activation Analysis using¹²B with 20-ms half-life. The performance characteristics of the system are presented and boron determinations of NBS standard reference materials as well as fertilizer materials are compared by literature value and spectrophotometric measurements, respectively. In both cases good agreement is obtained.     

Trace-element analysis of argyle diamonds using instrumental neutron activation analysis

Thirty four elements were determined by instrumental neutron activation analysis in colourless, brown, and pink diamonds, with and without inclusions. These were compared with data obtained for similar elements in the host lamproite rock. The natural radioactivity of these samples was measured by instrumental techniques, and found to be negligible.     

Cumulative neutron activation of short-lived radionuclides for the analysis of large samples in mineral exploration

Cumulative neutron activation is used to determine mg/kg concentrations of gold in rock samples, weighing 10 g. Twenty 0.5 g replicates are irradiated in an epithermal-neutron flux for 5 s and counted for 14 s. The twenty spectra are summed, and gold is measured with the 279 keV gamma-ray of^197mAu (7.2 s). Total analysis time for a 10 g sample is 400 s and detection limits around 2 mg/kg are achieved in gold ores, sulfides and silicates.     

Anticoincidence counting further improves detection limits of short-lived products by pseudo-cyclic instrumental neutron activation analysis

A systematic investigation was carried out on the merits and limitations of anticoincidence counting for short-lived radionuclides (t _1/2 < 75 s) used in instrumental neutron activation analysis (INAA) and pseudo-cyclic INAA (PC-INAA) methods for single as well as simultaneous multielement determinations in botanical and nutritional reference materials. The list of radionuclides of interest included: ¹⁰⁸Ag, ¹¹⁰Ag, ^165mDy, ²⁰F, ^75mGe, ^179mHf, ^86mRb, ^46mSc, ^77mSe, and ^177mYb. Precision and accuracy of measurements were good, and detection limits were of the order of µg kg^?1.     

Photoactivation analysis of ores using short-lived radionuclides

The results of applying photoactivation for express nondestructive multicomponent analysis of apatite-nepheline, gold-bearing, polymetal and lapparite ores are presented. The experiments were carried out at the IPP microtron with bremsstrahlung of 10 to 15 MeV electrons. A setup with mixed gamma-neutron field was built and used for elemental analysis. Experiments show that such elements as P, Al, Ti, Ba, and Ce can be determined with a sensitivity of approximately 0.1 mass% and a statistical error of a few percents. These values are wholly satisfactory to modern demands of industry. Gold and silver can be successfully determined in gold-bearing ores on the level of grams per ton.     

Elemental analysis of local soda samples using instrumental neutron activation analysis

Nigerian soda samples have been analyzed for major, minor and trace elements using instrumental neutron activation analysis. The following elements were determined; Na, Sm, U, La, Cr, Eu, Zn, Hf, Fe, Sc, Ba, Rb, Cs, Co, Au, Yb, Lu, Th, Ce, Zr, Se, As and Ta. The samples appear safe to use in human diet, although they may still require industrial purification to bring down the level of nonessential elements and those that could be toxic when present at high concentration.     

Determination of uranium in ores using instrumental neutron activation analysis

An instrumental neutron activation analysis method based on the measurement of²³⁹Np has been developed for the determination of uranium in ores. The samples after 5 sec irradiation were cooled for 3 days and the gamma-ray spectra were measured with a 30 cm³ Ge(Li) detector. The precision and accuracy of the proposed method were determined by analysing IAEA Standard Uranium Ore samples.     

Study of size-fractionated coal-combustion aerosols using instrumental neutron activation analysis

The chemical composition of aerosols emitted during coal combustion was studied as a function of particle size down to 0.01 m. The aerosol collections were carried out in a 81 MW capacity boiler that burned Venezuelan coal in a circulating fluidized bed combustion chamber. The samples were analyzed with upstream of the electrostatic precipitator using a Berner low-pressure impactor, which was quipped with a cyclone pre-cutter to avoid overloading of the first impaction stages. The samples were analyzed by INAA for up to about 40 elements. The elemental concentrations in the particulate matter for each impaction stage were plotted as a function of stage number (particle size). For the elements Na, Al, K, Ca, Sc, Ti, V, Ga, La and Sm, the concentration variation was limited to a factor of 2 to 4, and the concentrations of these elements were lower for the initial and final impactor stages than for the intermediate particle sizes. The variations were also limited to a factor of 2–4 for Mn, Fe, As, Sb and Th, butall these elements showed increasing concentrations with decreasing particle size. Still other elements, such as Ni, Cr, Co, Za, W, Mo and the halogens, were highly enriched (up to 20–100 fold) in the fine particles when compared with the coarse particles.     

Erros in instrumental neutron activation analysis

Equations are derived for the statistical and systematic error in INAA. It is possible to use them for the definition of limits of decision, detection and determination.     

Errors in instrumental neutron activation analysis

Equations are derived for the statistical and systematic error in INAA based on single photopeaks. They may serve to predict the applicability of the method or to judge data obtained under well-known conditions.