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Abstract  

Recommended k0-factors and related nuclear data for use in (n, ) activation analysis are given for 72 isotopes. In addition the basic nuclear constants and experimental parameters needed in the k0 standardization method are reviewed. For convenient data reduction, computer programs were developed.

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Abstract  

Loess sediment was prepared and characterized with well-established K, Th and U contents, and corresponding 40K, 232Th and 235,238U activities, intended for use as a reference material in the annual radiation dose determination for luminescence dating. To this purpose, loess was collected in Volkegem, Belgium, and — after drying, pulverizing and homogenizing — characterized via k 0-INAA and HPGe gamma-ray spectrometry. This led to 12 kg material with a grain size below 50 μm, with established K, Th and U homogeneity, with the 232Th and 238U decay series proven to be in equilibrium, and with the following K, Th and U reference data: K = 16.5±1.5 g·kg−1 (40K = 497±45 Bq·kg−1); Th = 10.4±0.6 mg·kg−1 (232Th = 42.2±2.5 Bq·kg−1); U = 2.79±0.12 mg·kg−1 (238U = 34.5±1.5 Bq·kg−1; 235U = 1.59±0.09 Bq·kg−1; 235+238U = 36.1±1.7 Bq·kg−1). These data were confirmed via comparison with the results from NaI(Tl) field gamma-ray spectrometry, thick-source ZnS alpha-counting and thick-source GM beta-counting (after converting all data to Gy·ka−1). The reference material is available (as aliquots up to 200 g) from the Ghent Luminescence Laboratory to all interested luminescence dating laboratories upon motivated request.

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Abstract  

The practical applicability of the 1/E1+α epithermal spectrum representation and of the effective resonance energy

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in NAA is investigated. Attention is paid to fundamental considerations such as definitions and approximations, error propagation functions, uncertainty statements, reliability of nuclear data and formal dimensioning problems. As to the latter, it is concluded that the applicability of the
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-concept is not dependent on the choice of a reference energy. The usefulness of the parameters
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in NAA is demonstrated by new experimental evidence obtained from and Q0 determinations in three different reactors: the WWR-M reactor (Budapest, Hungary), the THETIS reactor (Gent, Belgium) and the DR-3 reactor (Risø, Denmark).

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Abstract  

The present paper shows that the effective resonance energy

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introduced by RYVES, is a useful parameter for the correction of resonance integrals in non-ideal epithermal neutron spectra, which can be approximated by a 1/E1+α-flux distribution. The definition, the characteristics and the calculation of
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are discussed thoroughly. Tabulations are included, giving
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for 96 isotopes.

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Abstract  

A new method is developed for instantaneous α-determination in the 1/E1+α epithermal neutron spectrum. It is based on coirradiation of three bare resonance detectors, followed by gamma-counting on a calibrated Ge(Li)-detector. The technique is applied in two channels of the Thetis reactor (Gent) and the results are critically compared with those obtained by other methods.

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Abstract  

One of the basic steps in luminescence dating is the determination of the annual radiation dose. Among the suitable determination methods in the case of sediment dating is HPGe gamma-ray spectrometry, primarily yielding the concentrations of K, Th and U via measurement of gamma-rays emitted by 40K and by 232Th and 235,238U and their decay products. These determinations involve both large-volume samples (with cylindrical or Marinelli geometry) and low-energy gamma-rays (down to the 210Pb 46.5 keV line). In view of this, calculations have been made in the present work in order to investigate possible inaccuracies related to gamma-ray attenuation, which may be different in samples and calibrants which have considerably different composition (elemental concentration and packing density). The calculations are based on the introduction of correction factors containing “effective solid angles” (proportional to the peak detection efficiencies), which are believed to give “correct” concentration results. It was found that, in some cases, significant errors could be committed when not performing proper corrections. Therefore, it is concluded that in practice this possible source of inaccuracy should be kept in mind, thus making it necessary to have a fair knowledge of the properties of the materials (samples and calibrants) under investigation.

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Abstract  

The induced activity of the99Mo isotope is mostly determined via the 140.5 keV γ-line, which is the strongest gamma-ray of its daughter,99mTc. Some recent literature, however, indicates a direct feeding of this energy level from the mother isotope as well. Considering the importance of this line in practice as well as the large controversy and scattering in relevant nuclear data available at present, a combined effort was made to remeasure this questionable absolute intensity. A relative method of irradiating a Mo-target with reactor neutrons and repeatedly measuring its (n,γ) induced activity relative to the 181.1 keV and 739.5 keV gamma lines of99Mo as internal references was used. The weighted average of different runs yielded γ(99Mo, 140.5 keV)=(5.07±0.37)%. As a consequence, when the 140.5 keV gamma line is used, the contribution from the99Mo mother isotope should always be taken into account, e.g. in neutron cross-section measurements and neutron activation analysis.

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Abstract  

k0- and Q0-factors of 18 short-lived nuclides used in reactor neutron activation analysis were determined using the Fast Irradiation and Measurement System (FIMS) of the TRIGA MARK II reactor at the Atominstitut der Österreichischen Universitäten. The Q0-factors were either critically selected from literature, or experimentally determined according to theCd-ratio method, while the k0-factors were additionally determined by theBare monitor method. A comparison is made with the values calculated by introduction of literature data for the input parameters. Moreover, a user oriented tabulation is presented of k0-, Q0-factors and related nuclear data. All results were critically tested with respect to their accuracy and precision.

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