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.
Authors:F. de Corte, K. Masumoto, A. De Wispelaere, and F. Bellemans
A dedicated NAA calibration method was developed for the determination of the neutron spectrum monitor elements Co, Au and Lu in alloyed wires and foils, with an accuracy of better than 1%. The method does not require quantitative micropipetting for preparing the standards, and leads to vanishing errors caused by flux inhomogeneities and by differences in counting geometry and gamma attenuation. Its performance was tested by analysing various NIST, IRMM and RX aluminium-based materials with certified or specified Co, Au or Lu content.
In order to calculate coincidence correction factors when measuring with a low-energy photon detector (LEPD), algorithms were developed for the description of the summing-out probabilities taking into account -LX in addition to - and -KX true-coincidences, where KX and LX can originate from internal conversion and electron capture. The accuracy of the calculation procedure is experimentally checked. The work presented here is part of an extension of the NAA k0-standardization to counting in a LEPD.
Authors:M. Freitas, F. De Corte, M. Gouveia, M. Prudêncio, and J. Cabral
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.
-values are calculated, and the correction procedure for the cascade coincidence effects is established by calculation of
the correction factor COI for five 130I γ-rays (418.0, 536.1, 668.5, 739.5, and 1157.5 keV).
Authors:Bangfa Ni, Pingsheng Wang, Huiling Nie, Shuyuan Li, Xuefeng Liu, and Weizhi Tian
A PC controlled automatic INAA system is briefly introduced. The unique features of the system in software, hardware, and quality control procedures are described. Major performances are given to show the analytical quality and productivity of the system.
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.
In order to assess the levels and behavior of129I (half-life: 1.6×107 y) and127I (stable) in the environment, we have developed analytical procedures involving neutron activation analysis (NAA). Environmental samples collected around Tokaimura, Ibaraki Prefecture, Japan, have been analyzed using this method. Ranges of129I and127I concentrations in surface soil were 0.9–180 mBq kg–1 and 1–60 mg kg–1, respectively. Higher129I concentrations were found in soil samples collected from coniferous forests, suggesting a contribution from tree canopies in the deposition of this nuclide. Most of the129I in soil, was found to be retained in the first 10 cm. The129I/127I ratios in wheat fields were lower than those in rice paddy fields.A soil sample collected by IAEA from an area contaminated by the Chemobyl accident was also determined. The129I concentration and the129I/127I ratio were 1.6 mBq kg–1 and 1.7×10–7, respectively. The129I level in this sample was higher than the values obtained in areas far from nuclear facilities in Japan. It was suggested that the analysis of129I in soils in the Chernobyl area may be useful in evaluating the131I levels at the time of the accident.Analyses of129I and127I by ICP-MS in water samples were also made. The analytical speed of this method was very high, i.e., 3 minutes for a sample. However, there is a sensitivity limitation for129I detection due to interference from129Xe with the129I peak. The detection limits for129I and127I in water samples were about 0.5 mBq ml–1 and 0.1 ng ml–1, respectively.
Authors:R. López-Valenzuela, J. López-Palacios, M. Jiménez-Reyes, G. Cataño, and D. Tenorio
Thirteen Teotihuacan-style ornaments of an incense burner were studied. Ceramic pastes, pigments and mica were analyzed by
neutron activation, X-ray diffraction and scanning electron microscopy. Elemental (Sc, Cr, Fe, Co, Rb, Cs, La, Ce, Nd, Sm,
Eu, Tb, Yb, Lu, Hf, Th and U) and statistical analyses of ceramic-body data showed that these pieces were made from the same
raw material, which is chemically different from the fine orange ceramic of Teotihuacan. Montmorillonite and the classical
components of sand were the minerals identified in the ceramic pastes. The white pigment contained calcium, titanium and aluminium,
the yellow pigment was ocher, and the red pigment was a mixture of red ocher and cinnabar, the binder of the pigments being
clay. Exoskeletons of diatoms and locust ootecs were found in the pigments. Mica was identified as biotite, identical with
that coming from Monte Alban Oaxaca. We wish to undertake a historical reconstrution of these ornaments based on archaeometric
and literature data.
Authors:S. Metairon, C. Zamboni, L. Kovacs, F. Genezini, N. Santos, and E. Vilela
Neutron activation analysis has been used to determine Br, Ca, Cl, K, Mg and Na concentrations in whole blood of patients
with chronic kidney disease (CKD) as well as in whole blood of normal individuals (control group). The dependence of the elements
concentration in function of sex, age, time and type of treatment were investigated. The similarities and differences between
healthy individuals and CKD are discussed.