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Abstract  

A new method is presented to calculate with improved accuracy the absolute peak efficiency of cylindrical Ge and Ge(Li) detectors for point, disk and cylinder sources, positioned at any source-detector distance. Moreover attention was paid to true-coincidence effects. The method is extensively tested and applied for the analysis of reference materials. The accuracy turned out to be 3% or better.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. De Corte, A. Simonits, F. Bellemans, M. Freitas, S. Jovanović, B. Smodiš, G. Erdtmann, H. Petri, and A. De Wispelaere

Abstract  

This paper reports on the contribution made by some cooperating laboratories to the further development of the k0-method. As to the extensions and improvements, emphasis is put on the availability of an Al–0.1% Au reference material for the k0-standardization of NAA, on the counting of large-diameter samples, on the use of a low-energy photon detector, and on the introduction of the Westcott formalism for the handling of non-1/v (n, ) reactions. A survey is given of a large variety of scientific and industrial applications, including the analysis of biological, geological and geochronological samples, various kinds of reference materials, high-purity products and ceramics, and a number of environmental pollution indicators. As shown, the advantage of the k0-standardization will be fully exploited with an increasing level of automation in NAA laboratories. Eventually, new measurements and evaluations of k0-factors and related nuclear data are given in an Appendix.

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Abstract  

In absolute or comparator standardization methods of (n,

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, introduced to correct for this effect, is reviewed.

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Abstract  

An account is given of the role and the strength of k 0-INAA to assess the annual radiation dose (contribution of U, Th, K and Rb) for use in TL/OSL dating of sediments. Mention is made of: (1) its simplicity of sample preparation, (2) its accuracy and even its reference character for other elemental determination methods, (3) the possibility of obtaining the Rb content with no extra effort and (4) its capability to easily and reliably quantify U and Th in a small amount of etched quartz grains, followed by evaluating the importance of their presence in the quartz inclusion technique.

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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.

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Abstract  

The present paper deals with the experimental determination and the critical evaluation of Qo, the ratio of the resonance integral (Io) to the 2200 m.s–1 cross-section ( o) for 57 analytically interesting (n, ) reactions, including a revision and updating of formerly published results for 13 isotopes. Full account is given for deviations from the ideal epithermal neutron flux distribution. The Budapest-Gent cooperative determinations, yielding parallel but independent results, lead to recommended Qo-values with an average uncertainty as low as 3%. Finally, with the aid of independently evaluated or measured o-data, a list of recommended Io-values is given.

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Abstract  

When making use of some single comparator or absolute standardization methods in reactor neutron and in epicadmium neutron activation analysis, the knowledge of the effective resonance energy (

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) is essential to correct for the effect of the nonideal epithermal flux distribution on the analysis result.
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can be calculated from neutron resonance data, but when these are incomplete, not accurate or even not known at all, experimental determination should be considered. Such a method, providing both
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and the resonance integral to 2200 ms–1 cross-section ratio (QO), is described in this paper. Results are given for 11 isotopes.

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Abstract  

The resonance integrals for 59 isotopes were determined by neutron activation in reactor Thetis. The irradiations were carried out with and without Cd cover. The ratios of the thermal to epithermal fluxes were calculated from the Cd ratio of a Au monitor. From the induced activities in 36 elements, measured by means of γ-spectrometry with Ge(Li) and NaI(Tl) detectors, the values of I0th were obtained.

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Abstract  

The Ree contents in lichens and plants determined by k0-standardized NAA with LEPD and HPGe are compared. We obtain similar values for Sm, Eu, Tb and Yb and better values for Ce and Nd by using LEPD Besides, LEPD allows the determination of Gd, Tm and Lu. The study of REE concentrations in the neighbourhood of two coal power stations show that: i) in the station under construction (C. T. Pego), the index of accumulation of each REE by the lichens and olive tree leaves is identical in two sampling loci where the soils have different REE concentration; and ii) in the station in operation (C. T. Sines), the REE contents in the soils is identical and the differences observed in the lichens and wild terrestrial plants are most probably due to the fly-ashes emmission from the station.

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Abstract  

The concept of the effective resonance energy

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, formerly introduced as a parameter in the absolute (e.g. k0-) standardization methodology of (n, ) activation analysis, is elucidated with respect to dimensioning, accuracy and usefulness.

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