Determination of molybdenum isotope abundances and ratios for nuclear samples analysis using Thermal Ionization Mass Spectrometry

This paper describes a protocol combining resin separations and thermal ionization mass spectrometry measurements to analyze the molybdenum isotopic composition of nuclear samples in glove box condition. The development of two separation protocols was undertaken in the absence of HCl, known to lead to issues in glove boxes conditions. The first one is the purification of Mo from Zr and Ru through the implementation of a single-stage separation process, utilizing the TEVA resin. The second one combines a separation using UTEVA and TEVA resins to purify Zr and Mo if both element isotope abundance must be analyzed. For both protocols, the recovery of the Mo was greater than 80%, and the decontamination factor of Mo in regard of Zr and Ru was greater than 700. The measurement of Mo isotope ratios on a purified Mo sample exhibited no statistically significant deviation from the reference values. The study of the main contributors to the isotope ratio uncertainties showed that: a reduction of the uncertainty of the certified value of the ⁹⁸ Mo isotope abundance is needed to improve the accuracy of the measurement using the internal normalization and a better measurement repeatability is needed to improve the uncertainty of the isotope ratios corrected using an external normalization. Then, the developed protocols were then successfully applied to three nuclear samples. The relative uncertainties of the isotope abundances of the main isotopes were estimated to be less than 1%.