Production of actinium, thorium and radium isotopes from natural thorium irradiated with protons up to 141 MeV

Cross sections of 225Ac, 227Ac, 227Th and 228Th in thorium-232 targets irradiated with protons in the energy range 21–141 MeV have been measured. Based on these data, production yields of 225Ac and 223Ra in thick thorium targets have been calculated. It is possible to produce in proton energy range 60–140 MeV about 96 GBq (2.6 Ci) 225Ac per 10-d irradiation with 100 μA proton beam current and 10-d decay, and much higher amount of 223Ra. The impurities of 227Ac and 224Ra are important and need to be assessed for further medical applications.