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Abstract  

The epithermal neutron spectrum shape parameter in nuclear reactors is explained from a theoretical point of view in terms of the neutron slowing down density function. The latter is approximated by Fermi's age theory. Values for are calculated for a simple approximation of a nuclear reactor: a disk shaped fission neutron source in an infinite graphite moderator. The model produces -values with the correct sign and magnitude, compared to experimental values from the literature, determined in a real reactor. It is shown that varies strongly with distance to the neutron source and less strongly with neutron energy. The inappropriateness of average -values, obtained from the slope of quasi-straight lines produced by log-log plots of E versus E, for the correction of non-ideal epithermal neutron activation is discussed. Conclusions are formulated concerning the impact of an energy dependent on comparator type NAA.

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Abstract  

Differential scanning calorimetry has been used to study the thermal effects during adsorption and desorption of water on different zeolite NaA samples. An attempt has been made to compare the thermal behaviour of a layer of zeoliete attached on metal ("by chemical bond") with zeolite powder pressed on metal. The dependence of the water uptake on temperature has been studied with a powdered sample. Isothermal measurements of the water uptake of the zeolite after activation, appeared the best way to determine the heat of adsorption. Calibration of the DSC was needed. The adsorbed amounts of water corresponding to the released heats were determined thermogravimetrically. Once the heat of adsorption is known, it is possible to determine the mass of active zeolite of thin synthesized zeolite layers on metal with DSC.

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AbstractAbstract  

The epithermal reactor neutron spectrum shape-factor
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for a given nuclide, are examined theoretically in great detail. First the necessity, meaning and importance of the choice of a reference neutron energy in a non-ideal spectrum (
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are discussed, showing that the relation between the reasonance integrals in ideal and non-ideal spectra cannot be described adequately by two independent parameters
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and
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independent of
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can be introduced by its use. It is shown that
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is dominated by the first lowest resonance energies for a given nuclide, making its vulnerability to literature updates of resonance parameters almost equal to those of individual resonances. The effect, on the epithermal and total activation of specific nuclides, of large systematic and statistical errors on
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and
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) and irradiation facilities (different
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is calculated for final NAA results in terms of concentrations, botained by a comparator technique based on the197Au reference nuclide. Conclusions are drawn concerning the impact of the foregoing on the usefulness of comparator type reactor NAA as an alternative to classical NAA using multi-element standards.
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Abstract  

Abstract Passive air samplers (polyurethane foam disks) were deployed at 25 urban sites and 66 rural sites over the period of July to October 2005, partly between October 2005 and January 2006 for about 120 days across China, and analyzed for extractable organo-chlorine /-bromine /-iodine (EOCl/EOBr/EOI) and polychlorinated biphenyls (PCBs) using hybrid neutron activation analysis (NAA) combined with gas chromatographymass spectrometry (GC-MS). The average concentration of EOCl, EOBr, EOI and ΣPCBs among all the sites were 173.7, 3.5, 1.0 and 0.74 ng/d, respectively. Higher values of EOCl/Br/I and PCBs were detected in the areas of high usage and high emission, which were linked to relatively high-income areas in China, while lower in the west ill-developed region of China, which indicated that these pollutants mainly came from industrial pollution. Higher EOCl contents in traffic areas stated that the exhaust emission from vehicle was another main source of organochlorines in the air. The relative proportions of the known organochlorines (84 PCB congeners) to total EOCl were 0.02–3.0%, which implied that most of EOCl measured in air were unknown.

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Abstract  

The neutron spectra of one outer (#10) and two inner (#2 and #3) sites of the Dalhousie University SLOWPOKE-2 reactor (DUSR) have been calibrated for the k 0-based neutron activation analysis (k 0-NAA). The parameters determined include the cadmium ratio (R Cd), epithermal neutron flux shape factor (), subcadmium-to-epithermal neutron flux ratio (f), thermal-to-fast neutron flux ratio (f F), modified spectral index r()(Tn/T0)1/2, Westcott g Lu(T n)-factor, and absolute neutron temperature (T n). The a-values of -0.0098±0.0045 and -0.0425±0.0047 and -0.0422±0.0053 and f-values of 57.1±2.2 and 18.8±0.4 and 18.9±0.4 were obtained for the sites #10, #2 and #3, respectively. The modified spectral index (MSI), g Lu(T n)-factor, and T n have been determined for the handling of non 1/v (n,) reactions. The accuracy of the method was evaluated by analyzing reference materials.

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Abstract  

The World Health Organization states that envenomation is responsible for a high number of deaths per year, especially in equatorial areas. The only effective specific treatment is the use of hyperimmune serum (antivenom). In Brazil, Crioula breed horses are used for antivenom production, with great importance in the maintenance of public health programs. A strict biochemical and metabolic control is required to attain specificity in antiserum. Inorganic elements represent only a small fraction of whole blood. Nonetheless, they play important roles in mammalian metabolism, being responsible for controlling enzymatic reactions, respiratory and cardiac functions and ageing. In this work, whole blood samples from Crioula breed horses were analyzed by EDXRF technique. The reference interval values were determined for the elements Na (1955–2013 μg g−1), Mg (51–75 μg g−1), P (523–555 μg g−1), S (1628–1730 μg g−1), Cl (2388–2574 μg g−1), K (1649–1852 μg g−1), Ca (202–213 μg g−1), Cu (4.1–4.5 μg g−1) and Zn (2.4–2.8 μg g−1) and a comparative study with NAA results was outlined. The samples were obtained from Instituto Butantan. Both techniques showed to be appropriate for whole blood sample analyses and offer a new perspective in Veterinary Medicine.

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Summary  

Ceramic samples found in San Miguel Ixtapan, Mexico State, Mexico, were analyzed by means of NAA, PIXE, SEM and XRD. Statistical treatments such as bivariate cluster and principal-components analysis were applied to the data set. The origins of these ceramic samples were classified as local, regional and foreign.

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Summary  

The use of a Zr-Au-Lu alloy allows the simultaneous determination of all neutron spectrum parameters relevant to the k- 0standardization of NAA, in terms of both the Høgdahl and the Westcott convention. The present paper reports on the fundamental aspects (theoretical considerations, desired composition; gamma-spectrometry protocol) of this “all-in-one” alloy and on the experimental results (radiation stability; homogeneity tests) obtained for a variety of prototypes that were produced by some firms specialized in alloying technology. It is concluded that for the most recently produced material all criteria are fulfilled to pass on to the development of a certified Zr-Au-Lu alloy, which would be quite useful not only in the practice of k- 0NAA, but for neutron spectrum monitoring in general.

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Abstract  

After 36 years of operation, reactor Thetis at the Institute for Nuclear Sciences (Ghent University) was decommissioned in December 2003. On this occasion, a survey is presented of the characteristics and features of Thetis, which were opening the way to its significant contribution to NAA and its leading role in the development of the k 0-standardization. A summary is given, including a few specific examples, of fundamental analytical developments and practical applications based on irradiations in the reactor Thetis.

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