The results of the determination of uranium in Mongolian brown coal, coal ash, phosphate rock, and technological samples by X-ray fluorescence (XRF) spectrometry are presented. Technological samples were produced from phosphates by chemical treatment. Powder geological samples and Certified Reference Materials (CRMs) were pressed as tablets. For chosen conditions of the sample preparation procedure analytical figures of merit were carefully studied, as exemplified by the rock and uranium ore Reference Materials. The variance of the total uncertainty is 2 % for uranium in the analyzed samples, and one is 7 % in the rock CRMs. The estimated values of the uranium detection limit for the CRMs are within the interval from 1 to 3 ppm. For the correction of the matrix effects the background standard method was used. Values of the uranium contents in the studied samples vary within the interval from 3.0 to 35.0 ppm.

The comparison of the wavelength dispersive (WD) XRF results with the energy dispersive (ED) XRF results and the neutron activation analysis (NAA) was performed. It is demonstrated that the WDXRF have satisfactorily agreed with the EDXRF results and the NAA within the limits of the uncertainty. It is shown that the values of the relative discrepancies between the WDXRF and EDXRF results are in the range of 2.0-18.0 %, and between the WDXRF and the NAA results are in the range of 2.0-20.0 %. These values are less than 30 %, yielding the third category of the precision of the mineral raw material analysis.

Keywords: X-ray fluorescence spectrometry, XRF, uranium content, background standard method, coal ash, coal, phosphate ore, technological sample

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