After critical evaluation of a number of existing standardization methods a new approach introducing generalized k0-factors was suggested in 1975 for use in (n, γ) reactor neutron activation analysis (RNAA). In order that the new method
could soon be applied competitively in actual analytical work a cooperation between the Activation Analytical Laboratories
of the Central Research Institute for Physics (KFKI), Budapest and the Institute for Nuclear Sciences (INW), Gent was established
to determine the k0 and other related nuclear data (Q0, T1/2, Ēr, etc.) with a high accuracy, to develop procedures for monitoring essential irradiation and measuring parameters (Φs/Φe, α, ∈p,
, etc.) as well as to share experiences when applying the method. This paper summarizes the main results of this cooperative
work obtained in the last five years. The current status and recent developments in the k0-method are reviewed and a “Status and Request List” compiled from more than a thousand surveyed nuclear data on about 150
analitically important (n, γ) reactions in being prepared to suggest new or refined measurements and to prevent the use of
An application of a new standardization method for rapid activation mass analysis with registration of the strongly absorbed low-energy gamma radiation is described. This method makes it possible to avoid the use of the time-consuming and laborious method of Internal Standard.
Instrumental neutron activation analysis (INAA) for traces and major elements of several geological samples from “Zgounder”
region in Morocco was performed utilizing the k0-standardization method. Sample irradiation has been done by the 250 kW Triga Mark II reactor at Jozef Stefan Institute in
Slovenia. Due to its accuracy, sensitivity and specificity, the k0-standardization method is the most suitable method for non-destructive multielement analysis mainly for trace elements in
rocks. It requires an accurate knowledge of the parameters of the irradiation facilities and other instrumentation parameters.
It is an absolute standardization method, where the absolute nuclear data are replaced by a nuclear constant, the k0-factor, determined experimentally with high accuracy. More than 40 elements were determined using about 30-second short and
about 7-hour long irradiations. Gamma-rays emitted from the irradiated samples have been determined by a high purity germanium
detector. Accuracy was assessed using the standard reference material AGV-1. This was less than 1% for major elements and
about 5% for traces.
Two widely used neutron activation analysis (NAA) standardization methods (relative and k0) have been validated at the Ghana Research Reactor-1 (GHARR-1) Centre using environmental and biological standard reference materials (SRMs). The samples were IAEA Soil-7 as an environmental sample, and NIST Orchard Leaves 1571 as a biological sample. The qualitative and quantitative analyses were done using a high resolution Canberra N-type high purity germanium (HPGe) detector. The accuracy and precision were evaluated for the elements analysed. The concentrations of most of the elements were found to be within 10% of the certified values. Precision was calculated from six replicate measurements and was found to be within 15%.
An analytical procedure has been developed for neutron activation analysis of ceramic powders, it is mainly based on the application to the Ko standardization method and on the use of pelletizing for sample preparation. Precision and accuracy have been checked through the analysis of international standards. The procedure was applied to a commercial silicon carbide sample for the determination of 42 elements. Results were interpreted in terms of repeatability and accuracy by comparison to other trace analysis techniques. Additional short half-life elements were also determined by the Ko method.
The use of thek0-standardization method in instrumental neutron activation analysis gives good accuracy and precision. The analysis time can
be reduced drastically by employing software for thek0-standardization calculations. In this work samples were irradiated in a TRIGA reactor and the gamma spectrum was analysed
by Sampo 90 and thek0-standardization by the KAYZERO/SOLCOI code (DSM Research). The efficiency measurement and the peak to total ratio at the
reference and other geometries were measured and tested for their accuracy by analysing some reference materials. Reference
materials such as SRM 1572 (Citrus leaves), SRM 1573 (Tomato leaves), SRM 1575 (Pine needles), IAEA Soil-7 (Soil) and SRM
1646 (Estuarine sediment) were analysed for the major, minor and trace element contents. The results were in good agreement
with the certified or literature values. The recently released IAEA 140 (Sea plant homogenates) was also analysed for 28 elements.
The k0-standardization method of INAA (instrumental neutron activation analysis) was applied to three reference materials: NIST (National Institute for Standards and Technology, Washington, D.C., USA) SRM (Standard Reference Material) 1646 Estuarine Sediment, NIST SRM 2704 Buffalo River Sediment and IAEA (International Atomic Energy Agency) CRM (Certified Reference Material) SL-1 Lake Sediment. Among the 50 elements sought yielding long-lived radioisotopes after (n, ) activation, for 32 elements numerical values were obtained, and for the remaining 18, only detection limits were estimated. When comparing the results obtained in this work to certified, recommended or other literature values, good agreement was found, proving that the same analytical procedure can be applied with confidence for analysis of environmental sediment samples.
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.
The k0-standardization method of neutron activation analysis (NAA) is very sensitive to the irradiation and counting time during measurement of the induced radionuclide by -spectrometry on the HP Ge detector. If the irradiation and counting time of the sample and co-irradiated standard is relatively short or the decay constant small, the application of the standard equation in the software for the specific count rate may become numerically unstable and the program aborts. In this work, attention is focused on the direct influence of saturation and "measurement" factors on the specific count rate for simple decay and for more complex types calculated directly by exponential functions, and by an alternative form using a truncated Taylor's series expression.
In recent years the k0-NAA method has been applied and developed at the 500 kW Dalat research reactor, which includes (1) the establishment of a PC database of k0-NAA-related nuclear parameters, e.g., radionuclide produced, half-lives, k0-factors, Q0, r, Eg, etc; the access to the database is able by a k0-NAA software or by manual; (2) the detection efficiency calibration of gamma spectrometers used in k0-NAA, (3) the determination of reactor neutron spectrum parameters such as a and f factors and neutron fluxes in the irradiation channels, and (4) the validation of the developed k0-NAA procedure by analysing some SRMs, namely Coal Fly Ash (NIST-1633b), Bovine Liver (NIST-1577b) and IAEA-Soil7. The analytical results showed the deviations between experimental and certified values were mostly less than 15% with most Z-scores lower than 2. The k0-NAA procedure established at the Dalat research reactor has been regarded as a reliable standardization method of NAA and as available for practical applications, in particularly for airborne particulate and crude oil samples.