In Parallel computation efficiencies were tested using 1 to 256 cores for calculations on the UO2 2⁺ molecule, yielding good efficiencies for both CASCI and CASPT2, except for some unexpected anomalies. As a test calculation for quantitative analysis, large-scale RASCI-RASPT2 calculations for the ground and excited states of UO2 2⁺ were performed to evaluate vertical excitation energies.