Isolation and quantification of a 93Mo isotope solution from proton irradiated niobium

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.

Preparation of 93Mo solution using proton irradiated Nb

93Mo is an important long-lived radionuclide in nuclear waste, and is required to be measured during the characterization of decommissioning waste. However, no commercial 93Mo solution is available to be calibrated and used as standard in the analysis of nuclear waste. This work presents a method for separation of 93Mo from Nb metal used in cyclotron as a target holder and irradiated with protons for long time. The separation of 93Mo from Nb matrix was implemented by combination of precipitation and chromatographic separation. The Nb matrix was first removed by precipitating oxides-hydroxides of Nb (e.g. Nb2O5) and then by Fe(OH)3 co-precipitation; Mo in the solution was purified using an alumina (Al2O3) column. A decontamination factor of ca. 105 was achieved for Nb. A pure carrier-free 93Mo solution was successfully prepared, and the 93Mo purity was verified by liquid scintillation spectrometry.