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Description
The Institute of Nuclear Physics of the Republic of Kazakhstan (INP RK) has developed a complex of nuclear-physical methods of analysis, among which instrumental neutron activation analysis (INAA) takes a significant place. To carry out studies on short-lived radionuclides (SLR) in a dry horizontal channel with neutron flux density 1012 particles/s/cm2 an automated pneumatic transport system (PTS) is installed. Spectra are recorded on a Canberra horizontal gamma spectrometer consisting of a semiconductor coaxial detector GC2018 (resolution 1.8 keV for the 60Co gamma line with energy 1332.5 keV, relative efficiency 20%) and a multichannel digital analyser DSA-1000. The process of PTS control is carried out with the help of special software allowing to choose irradiation modes, dwell time in the channel of the reactor zone of the WWR-K nuclear reactor, possible time of «cooling down» before the beginning of registration and directly the registration of gamma radiation spectra of induced activity itself. It is possible to record spectra serially at certain time intervals.
The method of INAA by SLR allows the determination of a whole range of elements: Na, K, Al, Cl, Ca, V, Mn, Mg, Cu, Co, Ba, Eu, Dy, In, Sr and others, among which most of them do not have long-lived isotopes and are determined by INAA method exclusively by SLR. This list significantly expands the list of elements to be determined and improves the sensitivity of determination of some of them. Application of the INAA method (including SLR) allows solving a number of scientific and practical problems for industry and production enterprises.
According to ISO/IEC 17025-2019 «General requirements for the competence of testing and calibration laboratories» accredited laboratories should use only certified and entered in the register of state measurement instruments (SMI) of analytical technique (AT). At present, both in the SMI of the RK and in the post-Soviet space there is no such AT for INAA on SLR. At present, such a method is being developed and will be certified in INP RK. It is planned that the developed AT will be used in one laboratory. The estimated date of submission to the SMI of the Republic of Kazakhstan is 2027.
In the annex to the industry standard for geological industry OST 41-08-212-04 [1] 22 ranges of element content from 0.2 µg/g (0.00002%) to 69.9% and the permissible mean square deviations of the analysis results (relative error), performed by methods of III category of accuracy are given. The normative base for development and certification of AT was studied, the ranges of element contents determined by the method of NAA SLR were determined. Algorithms for evaluation of metrological characteristics of AT - intra-laboratory precision, correctness and accuracy indicators are determined according to RMG 61-2010 [2]:
Samples of soil, ore, vegetation of different elemental composition were irradiated and analysed by the NAA method according to SLR. Samples with the contents of dysprosium, indium, titanium, vanadium, chlorine, aluminium, magnesium, manganese, calcium, copper were specially selected for the research. These samples were used for the set of experimental data for calculation of metrological parameters of the new created AT. From each sample 20 suspensions were taken. Sample irradiation was carried out in batches of 5 pieces to fulfil the conditions of intra-laboratory precision (the results of analysis are obtained by the same technique in the same laboratory under variation of different factors - time, operator). The study mode was selected experimentally and individually for each sample taking into account its composition to ensure the best spectral pattern of induced radiation. The spectra of induced activity of irradiated samples were recorded twice: after 10 minutes and 2 hours after the end of irradiation. The spectra were processed using Genie-2000 software. Element concentrations were calculated by the relative method using a set of standard samples.
Calculation of metrological characteristics of the NAA SLR AT is being carried out.
This work is carried out within the framework of budget financing of the Ministry of Energy of the Republic of Kazakhstan «Development of nuclear-physical methods and technologies for innovative modernization of Kazakhstan economy» IRN: BR23891691.
Literature
[1.] OST 41-08-212-04 Industrial Standard. Quality management of analytical work. Error guidelines for chemical analysis of mineral resources and precision classification of laboratory analytical techniques [Standart otrasli. Upravlenie kachestvom analiticheskih rabot. Normy pogreshnosti pri opredelenii himicheskogo sostava mineralnogo syr’ya i klassifikatsiya metodik laboratornogo analiza po tochnosti rezultatov]. Moscow, Russia, 2004 (In Russian)
[2.] RMG 61-2010 Recommendations on interstate standardization. State system for ensuring the uniformity of measurements. Indicators of accuracy, correctness, precision of methods of quantitative chemical analysis. Evaluation methods [ Rekomendasii po mejgosudarstvennoy standartizasii. Gosudarstvennaya sistema obespecheniya edinstva izmereniy. Pokazateli tochnosti, pravilnosti, presizionnosti metodik kolichestvennogo himicheskogo analiza. Metodi osenki.]. Moscow, Russia, 2013 (In Russian)
