Large-scale multiconguration Dirac-Fock calculations have been performed for the superheavy element eka-Thorium, Z = 122. The resulting atomic structure is compared with that obtained by various computational approaches involving dierent degrees of approximation, in order to elucidate the role that correlation, relativistic, Breit and Quantum Electrodynamics (QED) corrections play in determining the low-energy atomic spectrum. The accuracy of the calculations is assessed by comparing theoretical results obtained for Thorium with available experimental data. ; JRC.E.6-Actinides research