With a SLOWPOKE reactor, activation by epithermal neutrons is more important than for most other reactors. It was therefore undertaken to verify the accuracy of the k0 method for all elements with high Q0 values. Accurate standards of 40 elements were prepared and irradiated in the inner and outer irradiation sites of the Ecole Polytechnique SLOWPOKE reactor and then counted 10 cm from a 29% germanium detector and the amount of element in each case was calculated from the gamma-ray spectrum using the k0 method. For 13 nuclides with high Q0 values the results differed from the expected amounts by more than 5%, which suggests that measurements of new k0 and Q0 values are needed.
Authors:A. Di Piero, A. Di Piero, M. A. Bacchi, M. A. Bacchi, E. A. N. Fernandes, and E. A. N. Fernandes
The k0-method in INAA has been used at CENA/USP Brazil for analyzing geological and biological materials. With the acquisition of
a well-type detector, it was realized that the true-coincidence effects, originally corrected by semi-empirical procedures
with the in-house k0-software (Quantu-INAA), would affect the accuracy of results. Thus, new coincidence correction algorithms were developed,
based on a theoretical equation for obtaining the correction factors. Validation of the algorithms was performed by analysis
of plant certified reference materials.
An alternative convention for use in the k0-method describing the (n, )-reaction rate upon reactor neutron irradiation has been derived by dividing the cross-section in a (v)=
0v0/v part and a pure resonance integral, instead of splitting up the neutron spectrum. It describes the (n, )-reactions with the Westcott factor g(T)1 but without resonances below 0.35 eV, and should yield better results for those with resonances below this limit. The resulting formulas are simpler than the ones currently used. An important practical aspect of this new convention is that no irradiations under Cd-cover are needed to determine the parameters to be used in the k0-method. The parameters determined previously for (n, )-reactions with g(T)=1 can still be used.
Two samples of Napoleon's hair were received for determination of arsenic, mercury and other trace elements by INAA. Before sample irradiation, the hairs were washed following the IAEA washing procedure. Two standard reference materials of GBW09101 (human hair) and NIST/SRM1572 (citrus leaves) were analyzed along with Napoleon's hair for quality control. Standardization was conducted by applying the k0-method implemented in the program MULTINAA. The contents of arsenic and mercury as well as three additional elements chromium, antimony and zinc in Napoleon's hair are reported. Compared to the present normal levels, all of the determined elements in Napoleon's hair, except the mercury, are found to be irregular.
This work is about k0-INAA using unstable neutron flux for sample irradiation. Due to slow transport, each irradiation in the channel DBVK consists of three phases: stable irradiation at the final position, and two additional irradiations during travelling by exposure to an increasing neutron flux in the delivery course and to a decreasing neutron flux in the fetch course. In this work, the neutron flux distribution along this channel was calibrated and the neutron flux variation with irradiation time was calculated, making it possible to evaluate activity growth during a complete irradiation period. The feasibility of the k0-method was checked by analyses of four SRM-materials and three multi-element standards at three DBVK-positions. An accuracy of better than ±10% was found for nearly all determined elements in each determination.
Authors:S. Baechler, P. Kudejova, J. Jolie, and J.-L. Schenker
The k0-standardization method has been applied and evaluated at the cold-neutron prompt gamma-ray activation (PGA) facility of the Swiss spallation source SINQ (Paul Scherrer Institute). The k0-factors for 26 elements of interest were measured using chlorine as a comparator. The results showed good agreement with the values determined at other cold and thermal neutron guided beams, except for a few elements. Then, standard reference materials were analyzed to assess the accuracy of the method using the obtained k0-factors. Finally, the technique was used for multielement determination in various samples coming from nuclear waste storage, geochemistry and geology. In addition, the non-destructive nature of PGAA offered an interesting application in archeology.
Authors:Mohamed Soliman, Nader Mohamed, M. Gaheen, E. Saad, S. Yousef, and M. Sohsah
The k0-method of INAA standardization has been implemented using the irradiation facilities of the fast pneumatic rabbit and some
selected manually loaded irradiation positions, which designated for short and long irradiation, respectively, at Egypt second
research reactor. The neutron flux parameters (f and α) in each site have been determined using Zr–Au sets as neutron flux monitors. The reference materials coal NIST 1632c
and IAEA-Soil 7 were analyzed for data validation and good agreement between the experimental values and the certified values
Authors:S. Boulyga, I. Zhuk, E. Lomonosova, M. Kievetz, H. Denschlag, S. Zauner, A. Malenchenko, N. Kanash, and N. Bazhanova
k0-method of neutron activation analysis has been tested for applicability to the determination of trace elements in samples of thyroids of inhabitants from regions in Belarus affected to different degree by thyroid cancer among children after the accident of the Chemobyl power plant. It is shown that thek0-method produces results identical to the relative method in neutron activation analysis. Significant differences in the elemental composition of thyroids from the regions of Gomel and Minsk are observed and may be related to the different levels of occurrence of thyroid cancer among children.
Authors:J. Rao, E. Senthilvadivu, N. Seshadreesan, R. Acharya, C. Venkatasubramani, and A. Reddy
The pneumatic fast transfer system position at KAMINI reactor, Indira Gandhi Centre for Atomic Research, India was characterized
by determining the epithermal neutron flux shape factor (α) and the sub-cadmium to epithermal neutron flux ratio (f) for k0-based Neutron Activation Analysis (k0-NAA). For determination of α value, bare, Cd-ratio and Cd-cover methods were employed using dual and multi monitors namely
Au, Zr and Zn. For calculation of f, Au and Zr monitors were used in the case of bare method and Au monitor was used for cadmium ratio and cadmium cover methods.
The determined α-value of PFTS indicated a hard epithermal neutron spectrum and the f value indicated about 96 % thermal neutron
component. For validation of k0-NAA method, reference materials namely NIST SRM 1646a (Estuarine Sediment) and BCS Nb-stabilized Stainless Steel (BCS/SS
No.261/1) were analyzed. The percentage errors of the determined concentration values of elements were within ±5 % with respect
to the certified values and the Z-score values at 95 % confidence level were within ±2 in most of the cases.
The determination of very low concentrations of 237Np is of key-interest for environmental monitoring. The application of the k0-method to neutron activation analysis was not possible so far, since the k0-parameters were lacking. The parameters required for the k0-method are: the effective resonance energy r, the resonance integral (1/E) to 2200 m.s-1 cross section ratio Q0, and the k0 values. In this work, the experimental values of these parameters were determined by using two nuclear reactors with very different flux characteristics.