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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  

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 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  

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  

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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Abstract  

A simple and accurate method is presented to evaluate the burnup effects involved in the neutron activation of 197Au prior to any neutron flux characterisation, based on the spectrometry of the 198Au and 199Au decay gammas. The obtained burnup factor can be used as input for reactor neutron field characterisation techniques using 197Au(n,)198Au as a monitor. This way an iterative procedure is avoided.

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Abstract  

Some methods described in the literature for the determination of α in the 1/E1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements, thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods are applied in channel 15 of the Thetis reactor (Gent).

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