Determination of strategic metals in graphitic formations by the methods of neutron activation analysis with a californium source

The content of a number of strategic metals (Au, Sc, La, Sm, Eu, Dy) at the level comparable to their average contents in graphite-bearing rocks of the south of the Russian Far East was determined by the method of instrumental neutron activation analysis (INAA) on an original device with a radionuclide neutron source based on 252 Cf. A key advantage of INAA in analysis of difficult-to-dissolve carbon-containing materials is a non-destructive character of the method. The proposed methodological approach avoids the complex procedure of sample decomposition, analyte separation and associated problems (dissolution, contamination and losses). It is shown that there is no significant influence of carbon contained in the sample on the INAA results when up to 300 cm 3 of sample containing at least 87 %wt. of carbon are introduced into the activation zone. The detection limit of the method was calculated for a number of the determined elements. The possibility of determining the content of Sc, La, Sm, Eu, and Dy in natural high-carbon objects below the clarke level was confirmed. The absence of any significant dependence of the INAA results on the density and coarseness of the studied samples was revealed. The results of determining strategic metals in graphite-bearing metamorphic rocks of the south of the Russian Far East were compared for two different INAA options (reactor and with 252 Cf radionuclide source). The comparison showed that data obtained at the device with the radionuclide source 252 Cf for most of the elements under study match the results obtained earlier on a WWR-M reactor at the St. Petersburg Institute of Nuclear Physics named after B. P. Konstantinov. At the same time, the possibility to irradiate samples of 50 – 100 cm 3 ensures high representativeness of the sample when activated with the 252 Cf isotope. The INAA method with radionuclide source 252 Cf is suitable for the analysis of carbon-containing materials for trace elements, the determination of which is difficult due to complex sample preparation, analyte separation and other related problems.