Temperature and time dependence on extraction of Molybdenum-99 hot atoms from neutron-irradiated β-molybdenum trioxide particles into water

This study presents a novel perspective by examining the influence of temperature and heating time on the extraction of ⁹⁹Mo into water, contributing to a better understanding of its extraction kinetics. β-MoO₃ particles were synthesized <i>via</i> thermal evaporation and subsequently characterized using X-ray diffraction and transmission electron microscopy. These particles were then neutron-irradiated at the Kyoto University Research Reactor facility, after which the activity of the ⁹⁹Mo in the particles was analyzed by a high-purity germanium semiconductor detector. The irradiated β-MoO₃ particles were dispersed in water at temperatures of 20, 30, 40 or 50 °C for durations of 1, 2.5 or 5.5 h to extract ⁹⁹Mo. The associated β-MoO₃ solutions were also analyzed by a high-purity germanium semiconductor detector. The ⁹⁹Mo extraction efficiency was increased from 20.31 ± 1.24% to 66.88 ± 1.42% upon raising the water temperature and increasing the heating duration. The activation energy for this extraction process was found to be lower than that for simple atomic diffusion in crystalline MoO₃ and higher or close to that for the formation of or proton conduction in a hydrated MoO₃ phase. This result suggests that a hydrated MoO₃ phase accelerated the extraction of ⁹⁹Mo. To the best of our knowledge, this is the first research to investigate the temperature and time dependence in the extraction of ⁹⁹Mo hot atoms, providing a promising approach for large-scale production of ⁹⁹Mo/^99mTc radiopharmaceuticals.