Th-Spallation-Produced Ac with Reduced Ac Content.

Recent clinical results have demonstrated remarkable treatment responses of late-stage cancer patients when treated with alpha-emitting radionuclides such as actinium-225 (Ac). The resulting intense global effort to produce greater quantities of Ac has triggered a number of emerging technologies to produce this rare, yet important, radionuclide. Accelerator-based methods for increasing global Ac production capacity have focused on the high energy (>100 MeV) proton irradiation of thorium, despite the coproduction of the undesirable Ac byproduct at 0.1-0.3% of the Ac activity. We at TRIUMF have developed a process for the production of a Ra/Ac generator from irradiated thorium that results in an Ac product with reduced Ac content. Ac was separated from irradiated thorium and coproduced radioactive spallation and fission products using a thorium peroxide precipitation method followed by cation exchange and extraction chromatography. Stable and radioactive tracer studies demonstrated the ability of this method to separate Ac from most other elements, providing a directly produced Ac product with measured Ac content of (0.15 ± 0.04)%. A second, indirectly produced Ac product with Ac content of <7.5 × 10% is obtained by repeating the final extraction chromatography step with the Ra-containing fraction. The Ra-derived Ac showed similar or improved quality compared to the initial, directly produced Ac product in terms of chemical purity and radiolabeling capability, the latter of which was comparable with other Ac sources reported in the literature.