k0-NAA allows the simultaneous analysis of up-to 67 elements. Thek0 method is based on calculations using a special library instead of measuring standards. For an efficient use of the method,
the calculations and resulting raw data require optimized evaluation procedures. In this paper two efficient procedures for
nuclide identification and gamma interference correction are outlined. For a fast computation of the source-detector efficiency
and coincidence correction factors the matrix interpolation technique is introduced.
Variations in sample properties and sample geometry, such as filling height, sample density and chemical composition, were
found to have a much more significant influence on the full peak counting efficiency in gamma ray spectrometric analyses,
than variations in sample holder properties, such as wall and bottom thickness. This means that in attempting to guarantee
a consistent high quality of gamma ray spectrometric analyses one should focus on sample preparation. Sample holders do not
have to meet very high specifications.
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:R. van Sluijs, D. Bossus, J. Konings, F. De Corte, A. De Wispelaere, and A. Simonits
To account for varying dead time (frequently occurring when the measuring time is comparable with the half lives of the radionuclides in question) the use of Westphal's Loss-Free Counting technique (LFC) is preferable. However, standard gamma-ray spectrum deconvolution programs can not be applied in connection with LFC spectrometers, since this technique strongly influences the counting statistics of measured spectra. As consequence, erroneous results are likely to arise when applying peak search routines or when calculating the standard deviation of fitted peak areas or detection limits. To overcome these shortcomings, an LFC module equipped with Dual LFC Mode option should be used: this accumulates an LFC-corrected spectrum simultaneously with an uncorrected spectrum. The KAYZERO evaluation software has been modified to handle such tandem spectra.
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:W. Knaepen, W. Bergwerf, P. Lancée, W. Van Dijk, J. Jansen, R. Janssen, W. Kiezenberg, R. Van Sluijs, M. Tijsmans, K. Volkers, and P. Voors
Gas and oil companies frequently encounter build up of Naturally Occurring Radioactive Material (NORM) in their production and processing facilities. In the Netherlands NORM is subject to strict national regulations and, consequently, installations have to be screened on a regular basis. The availability of accurate and reliable NORM sampling and analysis techniques is therefore essential. A number of years ago, the Nederlandse Aardolie Maatschappij B.V. (NAM) actively initiated an investigation on analysis techniques for NORM samples from gas and oil companies. Within this framework, Shell Research Amsterdam organized a four-stage interlaboratory test programme in which representative samples of increasing complexity were analyzed by a number of Dutch institutes. Whereas a large spread in results was observed in the first stage, results in the last stage deviated less than ±10% from the values certified by an independent referee institute, even for comple, sludge samples. It was found that in particular the use of different values for the -yields and branching ratios amongst the institutes was responsible for the initial spread.
Authors:F. De Corte, A. De Wispelaere, R. van Sluijs, D. Bossus, A. Simonits, J. Kučera, J. Frána, B. Smodis, and R. Jaćimović
At the Special Sessionk0
of the MTAA-8 (Vienna, 1991), and later on at the Intemationalk0 Users Workshop-Gent (1992), progress was reported with respect to the development and use of computer codes in order to mould thek0-standardization of neutron activation analysis into an effective working instrument. Among others, this resulted in the software package KAYZERO for PC DOS, which was designed and distributed by DSM Research (Geleen, NL), and which is based on thek0-methodology, algorithms and nuclear data file developed and created at the INW (Gent, B) and the KFKI (Budapest, H), the traditional
k0-centres. One of the most recent initiatives is a project in the framework of the COPERNICUS programme of the Commission of the European Union. It uses the synergism of a Joint Research Project to give an impulse to the exploitation of KAYZERO-assisted NAA as a manageable and competitive analytical tool in industry and environmental sanitation in Hungary, the Czech Republic and Slovenia. An outline is given of the strategy worked out in this JRP, emphasizing the procedures applied in the three institutes for the calibration of their irradiation facilities and Ge-detectors, quality control and assurance procedures following the implementation of the method, and the identification and tackling of the practical analytical problems which are of relevance to the Central European partner countries.