Actinides are broadly used in several fields of science and technology, among other as catalysts in chemical processes [1, 2]. To characterize their behavior one often employs spectroscopic techniques, and among existing methods X-ray spectroscopy is particularly promising in the context of actinides given its great sensitivity and selectivity. With the introduction of advanced X-ray spectroscopy techniques and light sources in recent years, it has recently become possible to investigate different core states of uranium-containing complexes[3]. Analyzing such spectra requires theoretical models capable of describing the electronic structure of actinide species in the ground and excited states[4]. This, in turn requires the use of approaches describing both electron correlation and relativistic effects [5]. In this work we showcase the use of the Core-Valence-Separated Equation-of-Motion Coupled-Cluster Singles and Doubles (CVS-EOM-CCSD) framework [6] recently implemented in the DIRAC code [7] to obtain the core ionized and excited at the uranium Ledge in the gas phase (for the isoelectronic species UO 2+ 2 , OUN + and UN 2) and in a crystal environment (for UO 2+ 2 in Cs 2 UO 2 Cl 4). For the latter, we combine CVS-EOM-CCSD with the Frozen Density Embedding (FDE) method [8].