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.

Relativistic effects /Multiconfiguration Dirac-Fock method / Kurchatovium /Ground state SummaryRelativistic calculations of the electronic structure of the kurchatovium atom were carried out taking 468//-configurations into account. It was found that the ground state of Ku should be a J =2 level consisting mostly of the 6d7s 2 7p configuration (80%). The nearest level (lying « 0.5 eV higher) is the one with/= 2, in which the 6d 2 7s 2 configuration makes up 95%. The 7s 2 7p 2 configuration lies 2.9 eV above the ground state. It is concluded from the comparison of the orbital energies and multielectron levels of Ku and the atoms of d-and p-elements of group IV that, according to its chemical properties, kurchatovium must belong to d-, rather than to p-elements.

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