Advances in Sublimation Separation of Technetium from Low-Specific-Activity Molybdenum-99

Abstract

Two sublimation techniques have been developed to separate Tc from Mo to support accelerator production of 99Mo/99mTc. After bombardment, the metal target is dissolved in nitric acid, the solution is evaporated, and the precipitated solids are calcined to MoO3. In the first technique, MoO3 is melted to a 0.8 mm layer and oxygen is swept over the 835 °C sample at 30 std cm3/min. Small amounts of MoO3 vapors transported from the 835 °C sample are deposited above 550 °C onto the walls of a quartz tube in a temperature gradient of 4 °C/cm. Greater than 95% of released technetium oxide is collected in a 5 mL condenser at temperatures between 300 and 25 °C. In the second process, technetium oxide deposited on the surface of fine needle crystals of MoO3 is quantitatively released in an oxygen stream at 650 °C. The crystals are regenerated between milkings by dissolving in NH4OH, evaporating, and drying. In this initial work, greater than 90% product recovery is achieved by both processes during multiple milkings of 14 g Mo samples and a high-purity 99mTc product results at a concentration exceeding 500 mCi/mL in an isotonic saline solution.