Search Results

You are looking at 111 - 120 of 223 items for :

  • Refine by Access: All Content x
Clear All

Abstract  

A new Compton suppression system (CSS) for the gamma-ray spectrometer portion of the neutron activation analysis (NAA) was set up at the RPI/ITN. The pneumatic transfer system, SIPRA, for short-lived nuclides and cyclic irradiations was improved. A full calibration procedure of the CSS and SIPRA systems was performed. Two certified reference materials, NIST-SRM-1572 (Citrus Leaves) and NIST-SRM-1633a (Coal Fly Ash) were analyzed using the calibration factors. The CSS was instrumental in lowering the detection limits of Cr, Fe, Hg, Rb, Sr, Th and Zn by reducing background and/or spectral interference considerably. The analytical results were evaluated by comparison to the NIST certified values with deviations ranging from 2% to 8% for the above mentioned elements, except Zn ranging from 10% to 15% for biological and environmental samples, respectively.

Restricted access

Abstract  

Aerosols and source related materials (fly ash from refuse incinerators, vehicle exhaust and soil) were collected in April, 2002 in the northern areas of Jeju-do, Korea, and the Pb isotopic ratios (207Pb/206Pb and 208Pb/206Pb) of the samples were measured in order to estimate the Pb sources of the aerosols. The Pb isotopic ratios of the aerosols were classified into two groups, depending on the sampling date. One group showed similar Pb isotopic ratios with those of the source related materials, suggesting that the contribution of the regional sources to the aerosols was very large. The other showed different Pb isotopic ratios from those of the regional sources and relatively high Pb isotopic ratios compared to the ratios of the first group. The results suggest that in the continental Asia there seems to be a long range transport of Pb with high ratios in desert sands, which are carried by northwest seasonal winds.

Restricted access

Abstract  

A review is presented on the use of neutron activation analysis (NAA) for the analyses of coal, oil shale, tar sands and petroleum. Fast NAA has been widely used for the determination of oxygen, and to a limited extent, of other elements such as nitrogen and silicon. Reactor NAA followed by instrumental counting, and in specific cases, after radiochemical separations is discussed. Thermal and epithermal neutrons are both used. Limited use of the252Cf source has been made in fuel analysis. A complementary technique to NAA is the photon-activation analysis with linear accelerator. It can determine over thirty elements, many of them not possible to do by NAA. Round-robin analyses of standard coal, fly ash, or oil shale samples indicate nuclear activation methods are comparable in accuracy and precision to X-ray fluorescence or atomic spectrometric methods for most elements.

Restricted access

Abstract  

USGS BCR-1 and G-2, NBS 1633a Coal Fly-Ash and a 7-element synthetic standard for biological material have been analysed in this work by reactor NAA, using the k0-standardization method. The analyses were performed independently in the analytical laboratories of the Institute for Nuclear Sciences (INW), Gent, and the Central Research Institute for Physics (KFKI), Budapest. This procedure allowed not only a comparison with the specified data or with other published values, but enabled a check of the consistency of our own results obtained in largely different experimental circumstances. As concluded the k0-standardization method combines general versatility (with respect to irradiation and counting conditions) with good accuracy, while keeping the experimental work as simple as possible. Since the k0 method is a computer-oriented technique, a FORTRAN IV program was designed and applied on a VAX 11/780 machine.

Restricted access

Abstract  

Standard reference materials, normally used to check accuracy and precision of analytical methods or for interlaboratory comparisons, are proposed for use as multielement irradiation standards in neutron activation analysis (NAA). The advantages are simplicity of operation, and elimination of errors inherent in the preparation of a large number of synthetic standards at the trace element level. Examples of the approach are illustrated in the analysis of geological materials, soils, sediments, meteorites, lunar samples, coal and fly ash using the USGS diabase W-1 as the irradiation standard. Plant materials and animal tissue are analyzed using NBS Orchard Leaves as the irradiation standard. Best values for four popular SRM's (W-1, Bowen's Kale, Orchard Leaves, and Bovine Liver) are tabulated to facilitate further use of the proposed approach to multielement neutron activation analysis.

Restricted access

Abstract  

The k 0-method of standardisation for instrumental neutron activation analysis (INAA) has been used at the OPAL research reactor to determine the elemental composition of three certified reference materials: coal fly ash (SRM 1633b), brick clay (SRM 679) and Montana soil (SRM 2711). Of the 41 certified elements in the three materials, 88 percent were within five percent of the certified values and all determinations were within 15 percent of the certified values. The average difference between the measured and certified values was 0.1 percent, with a standard deviation of 4.1 percent. Since these reference materials are widely used as standards in the analysis of archaeological ceramics by INAA, it has been concluded that the INAA facility in Australia is particularly well-suited for nuclear archaeometry.

Restricted access

Abstract  

Concentrations of 35 elements in Chinese Standard Rocks (GSR-1 to GSR-3) and Soils (GSS-1 to GSS-8) have been measured with INAA using the SLOWPOKE reactor. At the same time, the U. S. NBS reference standards: SRM-1632a (Bituminous Coal), SRM-1633a (Coal Fly Ash) and SRM-1646 (Estuarine Sediment) were also analyzed in order to cross-check the accuracy of this method. The results obtained indicate that the reproducibility of the method is satisfactory for most of the elements, namely the precision in general, is better than ±10%. Comparison of our values for NBS SRM-1632a, 1633a and 1646 with the certified values of NBS or with values cited in the literature indicates good agreement. The results were found to be accurate within ±10% error of the established results.

Restricted access

Abstract  

The concentration of rare earths and other elements have been determined in the bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis (INAA). The samples and the standards soil-5, soil-7, coal fly ash and pond sediment were prepared and simultaneously irradiated for short and long time at the TRIGA Mark-II research reactor facility of Atomic Energy Research Establishment, Savar, Dhaka. The maximum themal neutron flux was of the order of 1013 n·cm–2·s–1. After irradiation the radioactivity of the product nuclides was measured by using a high resolution high purity germanium detector system. Analysis of -ray spectra and quantitative analysis of the elemental concentration were done via the software GANAAS, it has been possible to determine the concentration level of 27 elements including the rare earths La, Ce, Sm, Eu, Tb, Dy and Yb and uranium and thorium.

Restricted access

Abstract  

To order to examine experimentally the modified monostandard method implemented in the program MULTINAA, the FRM reactor in Garching (Germany) was calibrated and an INAA of a standard reference material NIST/SRMI1633b Coal Fly Ash was performed. The relative, thek 0-and the modified monostandard standardizations are applied. This work shows that for all of the examined 1/-nuclides the modified monostandard method provides identical analytical results to those determined by thek 0-method. For the non-1/ nuclides177Lu and152Eu the monostandard results are correct. Compared with the certified values of the analysed SRM1633b sample and also with the results of the relative method, it can be concluded that the modified monostandard method performed at our experimental conditions gives analytical results with accuracy better than 5%.

Restricted access

Abstract  

A permanent and stand-alone neutron-induced prompt -ray analysis (PGA) system, usable at both cold and thermal neutron beam guides of JRR-3M has been constructed. The characteristics of the system, including neutron beam and -ray spectrometer were measured. Owing to the absence of fast neutrons and the low -ray background, analytical sensitivities and detection limits better than those in other PGA systems have been achieved. Analytical results of ten elements in Standard Reference Material of Coal Fly Ash agreed well with those obtained by other methods. Isotopic analysis of Ni and its application to accurate and precise determination of Ni by stable isotope dilution method were performed.

Restricted access