Chemical Purification of Actinium-225 from Proton-Irradiated Thorium Targets

The chemical separation of actinium from proton-irradiated 232Th targets is being performed as part of a tri-laboratory (Oak Ridge National Laboratory, Brookhaven National Laboratory, and Los Alamos National Laboratory) effort focused on the accelerator production of 225Ac. Actinium-225 (t1/2 = 9.92 days) is produced by proton irradiation of a thorium metal target via the 232Th[p,x]225Ac reaction and can be used in targeted alpha therapy applications. The irradiation produces a suite of radioisotopes, including fission products, that must be chemically separated from actinium, as well as a vast excess of thorium. This separation is achieved by chemically processing irradiated thorium targets through a series of ion separation and extraction chromatography columns. This effort has produced purified 225Ac over 15 campaigns, providing material for use in targeted alpha therapy research and development. DOE, Office of Nuclear Physics, Isotope Program.