232Th-Spallation-Produced 225Ac with Reduced 227Ac Content

Recent clinical results have demonstrated remarkable treatment responses of late-stage cancer patients when treated with alpha-emitting radionuclides such as actinium-225 (225Ac). The resulting intense global effort to produce greater quantities of 225Ac has triggered a number of emerging technologies to produce this rare, yet important, radionuclide. Accelerator-based methods for increasing global 225Ac production capacity have focused on the high energy (>100 MeV) proton irradiation of thorium, despite the coproduction of the undesirable 227Ac byproduct at 0.1–0.3% of the 225Ac activity. We at TRIUMF have developed a process for the production of a 225Ra/225Ac generator from irradiated thorium that results in an 225Ac product with reduced 227Ac content. 225Ac 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 227Ac content of (0.15 ± 0.04)%. A second, indirectly produced Ac product with 227Ac content of