R. Hepburn, S. Tsubota
Keywords: mesoporous alumina, molybdenum retention, medical isotope generator
Summary:Mesoporous alumina is used as the adsorbent for retaining Molybdenum-99 in the Molybdenum/Technetium generators used for medical imaging. Highly enriched uranium (HEU) has been historically used to create radioactive molybdenum for this purpose. However, in 2014 a global initiative was agreed upon to minimize and then eliminate the use and production of HEU for non-military applications. Shortly thereafter there was a call to find alternative methods to produce molybdenum-99, including the use of low enriched uranium (LEU) as well as other methods not requiring the use of uranium. In general, when non-uranium based methods of producing molybdenum-99 are employed, there is a lower concentration of molybdenum generated. This has created a need for a mesoporous alumina than can retain more molybdenum than what is currently available in order for the performance of the isotope generator not to suffer when non-uranium based molybdenum is utilized. Initial research was focused on creating mesoporous material with higher and higher surface areas. Our research has shown that the pore size of the mesoporous alumina and not the surface area is more predictive of the molybdenum retention performance of the mesoporous alumina. Mesoporous alumina with pore sizes ranging from 5nm to 19nm have been tested and the retention of molybdenum increased by a factor of 6. A variety of pore forming agents and templating materials were chosen to modulate the pore size. Addtionally, pore size and surface area were adjusted by varying the sintering temperature to limit the amount of densification.