The extremely neutron-deficient even-even uranium isotopes( 216,218)U were produced in the complete-fusion reactions induced by impinging Ar-40 and Ca-40 ions on W-180,W-182,W-184 targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-alpha-correlation method. The improved ground-state to ground-state alpha-decay properties of( 216,218)U were reported in [Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502 (2021)]. In this paper, we report on new alpha-decay activities with E-alpha = 10 163(27) keV for 216U and E-alpha = 10 073(16) keV for 218U, which decay from the 8(+) isomeric states of( 216,218)U into the 2(+) states of their daughter nuclei Th-212,Th-214, respectively. The new results extend the systematics of the alpha-decay fine structure for the N = 124 and 126 even-even isotones.