[en] The source can be used to advantage for calibration and adjustment of probes in gamma spectrometric determination of uranium for operating tests of chemical processing of uranium raw materials. The source is based on uranium enriched with ²³⁵U to 2 - 10%. It emits a radiation spectrum virtually identical to that of products and media in uranium ore treatment. Significant is the similarity of the spectra in the energy ranges 60 to 120 keV and 140 to 210 keV. The source can easily be manufactured in form of a solution supplied in a constant shape cuvette, or it can be part of a suitable solid carrier. (M.D.)