Authors:S. Van Lierde, F. De Corte, R. van Sluijs, and D. Bossus
A revision is made of some activation-decay types in k0-NAA, aiming at the removal of (1) the inconvenience that a long-lived daughter radionuclide could in some instances only be measured after complete decay of a shorter-lived mother, and (2) the simplification that in some cases the measured gamma-ray emitted by the daughter radionuclide is not significantly contributed to by the mother. In view of this, new experimental and generalized k0's and related data [Q0, k0(m)/k0(g), etc.] for some analytically relevant activation-decay cases are presented for implementation in an updated version of the "Kayzero" software package. These cases are: 60mCo-60Co, 104mRh-104Rh, 109mPd-109Pd-109mAg, 122mSb-122Sb, 134mCs-134Cs, 199mPt-199Pt-199Au. For completeness, recent data for two additional cases are also included: 80mBr-80Br, 124m2Sb-124m1Sb.
Authors:A. Simonits, F. De Corte, S. Van Lierde, S. Pommé, P. Robouch, and M. Eguskiza
The k0 and Q0 values for 94Zr(n,)95Zr(E = 724.2+756.7 keV) and 96Zr(n,)97Zr(
–) 97mNb (E = 743.4 keV) were re-investigated. The aim was to further improve the reliability of the neutron spectrum characterization (f and monitoring) in k0-NAA, based on "bare monitor" methods with the use of these Zr radionuclides. So as to achieve this goal, experimental determinations were performed in three reactor centers: KFKI AEKI, Budapest (WWR-M reactor); INW, Gent (THETIS reactor); SCK·CEN, Mol (BR1 reactor). The results were: Q0(94Zr) = 5.306; Q0(96Zr) = 251.6; k0(95Zr, 724.2+756.7 keV) = 2.000E-4; k0(97Zr/97mNb, 743.4 keV) = 1.237E-5. This means that the newly evaluated k0-values are about 4.7% lower than the formerly reported ones. It is also emphasized that the 97Zr half-life is 16.74 hours, contrary to the 1% higher values usually reported.
Authors:Lin Xilei, F. De Corte, L. Moens, A. Simonits, and J. Hoste
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.
Authors:T. El Nimr, F. De Corte, L. Moens, A. Simonits, and J. Hoste
The applicability of the k0 standardization concept in ENAA has been investigated by comparing for 32 isotopes the experimentally determined ke, 0-values with those calculated from well-known k0 and Q0=l0/σ0 factors. It is concluded that the k−-comparator method can be extended and applied in general to epicadmium (n, γ) activation analysis. Attention is also paid
to some specific problems, such as the deviation from the ideal epithermal neutron flux distribution, the uncertainty in the
effective Cd cut-off energy for the Cd-covers used, and the cadmium epithermal neutron transmission factor for which a literature
survey is presented.
Authors:R. Van der Linden, F. De Corte, P. Van den Winkel, and J. Hoste
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 I0/σth were obtained.
Authors:F. De Corte, S. Hossain, D. Vandenberghe, and P. Van den Haute
It was demonstrated that for the determination of the annual radiation dose for use in luminescence dating of sediments, one
should be aware of possible material inhomogeneities when applying analysis methods (such as k0-INAA) with sample intakes of the order of the gram (to be compared with Ge gamma-ray spectrometry in cylindrical or Marinelli
geometry, the latter involving ∼1.5 kg material). Moreover, when trying to remove the inhomogeneity, care should be taken
to avoid contamination of the elements investigated, especially in the case of low (K, Th, U)-content sand with a considerable
abrasive action (such as the Ossendrecht coversand dealt with in the present work). Whereas contamination was indeed shown
to happen when grinding the material in a porcelain mortar, a satisfactory technique proved to be agate-ball milling.
Authors:F. De Corte, S. Hossain, S. Jovanovič, A. Dlabač, A. De Wispelaere, D. Vandenberghe, and P. Van den Haute
A study is made of the corrections that are needed in the evaluation of the annual radiation dose, for use in TL/OSL-dating, via NaI(Tl) field gamma-ray spectrometry (monitoring of K, Th and U), calibrated via voluminous blocks that are simulating the Auger hole measuring conditions. Two cases are considered: the Heidelberg granite calibration block, which was found to be quasi-infinite, and the Oxford concrete calibration blocks, for which effective concentrations of elements are reported so as to account for their non-infiniteness. The calculations, via the software package ANGLE, are based on the concept of effective solid angles for Marinelli geometries.
(bulky source counted at the top of detector), discrepancies were below 7% in the whole range of gamma-energies considered (88–1115 keV), with an average of 3–4%. EXTSANGLE is extensive and flexible with respect to the data input, storage and output, thus contributing to the automation of a gamma-spectrometry laboratory dealing, for instance, with the k0-NAA and/or environmental radioactivity monitoring.
Authors:R. van Sluijs, D. Bossus, M. Blaauw, G. Kennedy, A. De Wispelaere, S. van Lierde, and F. De Corte
True-coincidence summing correction is an essential element in k0-based NAA1 and becomes important when samples are counted with a high efficiency detector. This may be the case where large detectors are used or where samples are counted in or in the vicinity of the detector in order to achieve low detection limits in conjunction with low-flux reactors. In some laboratories coincidence correction is accomplished by calculating the coincidence correction factors. Since experimental validation of the calculations will reveal only the most significant errors and is a laborious task due to the high number of radionuclides involved, three laboratories decided to compare their calculated coincidence factors. Each laboratory uses a different software package. A comparative performance analysis was made of COINCALC developed at the INW of the University of Gent (implemented in SOLCOI by DSM Research), the software of the IRI, University of Delft, the Netherlands, and the software of the Ecole Polytechnique, Montreal, Canada. The overall approach, data and algorithms were chosen independently by each institute as the software was being developed and, so, the comparison has yielded a number of interesting conclusions. A follow-up investigation of the discrepancies found will probably allow the performance of each program to be improved.
Authors:F. De Corte, M. Dejaeger, S. M. Hossain, D. Vandenberghe, A. De Wispelaere, and P. Van den Haute
Recently, in our laboratory an intercomparison was made of methods for the annual radiation dose determination (assessed from direct radiation counting and/or from the measurement of the K, Th and U contents) applied to luminescence dating of loess and sand sediment, whereby the emphasis was put on their precision and accuracy. Although these properties are important, the duration of the measurement is also a practically relevant aspect. Indeed, direct alpha, beta and gamma-counting can last a week or more, and the determination of K, Th and U via NAA can take up to three weeks to enable proper gamma-ray spectrometry of the long-lived 233 Th/233Pa. Therefore, in the present work the performance of k0-based epiCd-NAA (ENAA, with irradiation under a cadmium cover) when applied to sediments is compared to k0-NAA. As concluded, with the use of k0-ENAA the analysis turnaround time could be considerably reduced from ~3 weeks to ~ 2.5days, while maintaining satisfactory accuracy, precision and determination sensitivity.