Determination of ⁹³Mo in Radioactive Samples of Sulfuric Acid Media from Nuclear Facilities

⁹³Mo is an important radionuclide in view of radioactive waste repository because of its long half-life and high mobility in the environment. ⁹³Mo decays by electron capture without any measurable gamma ray emission. The concentration of ⁹³Mo in most of the radioactive waste is many orders of magnitude lower than the major activation product radionuclides, which makes the accurate determination of ⁹³Mo a big challenge. A new analytical method for the determination of ⁹³Mo in sulfuric acid media from nuclear power reactor was developed. ⁹³Mo was separated from most of the radionuclides by cation exchange chromatography followed by the removal of sulfate by CaSO₄ precipitation. A further purification of ⁹³Mo, especially from anion species of ⁵¹Cr and ¹²⁵Sb, was achieved by anion exchange chromatography and a short alumina column separation. The chemical yield of ⁹³Mo in the entire separation procedure reached about 75%, and the decontamination factors for all potential interfering radionuclides were 1.5 × 10⁶-1.6 × 10⁸. The purified ⁹³Mo was measured by liquid scintillation counting through counting its low-energy Auger electrons. A detection limit of 2 mBq/g for ⁹³Mo in 50 g sample was achieved by this method, which enables the quantitative determination of ⁹³Mo in most of the radioactive samples in the decommissioning waste and coolant water of nuclear power reactors. The developed method has been successfully applied to determine ⁹³Mo in coolant water of nuclear power reactors, providing a robust analytical approach of ⁹³Mo for the radiological characterization of radioactive wastes.