Production of Pa by proton irradiation of Th at the LANL isotope production facility: Precursor of U for targeted alpha therapy.

Uranium-230 (t = 20.8 d) is an alpha-emitting radionuclide that has potential application in targeted alpha therapy (TAT) of cancer. Its parent isotope Pa (t = 17.4 d), can be produced by proton irradiation of thorium metal targets. Preliminary Pa production runs were performed at the Los Alamos National Laboratory Isotope Production Facility (LANL-IPF) using thin thorium metal targets and a proton beam energy of 15-30 MeV, followed by radiochemical separation of Pa from the irradiated target matrix. The measured Pa production yields were found to exceed the predicted values in most of the experiments that were performed. This data will inform further production efforts for providing Pa/U for clinical trials.