Structural representation of the box-shell incorporation model of the incorporation of Cr into the UO 2 lattice matrix forming (Cr +3 x U +4 1x )O 20.5 x as derived from the EPR, HERFD-XANES and EXAFS analysis of this investigation. The 1st box-shell (purple) highlights the Cr +3 cation incorporation which involves the formation of an oxygen vacancy defect, V O , for charge compensation. The 2nd box-shell (cyan) indicates the locally distorted U lattice region derived from EXAFS analysis which showed shorter CrU distances resembling an environment closer to UO 3 or CrUO 4 than that of UU in pristine UO 2 . The 3rd box-shell (dark blue) which resembles closely that of the U +4 O 2 lattice, i.e., far enough away from the Cr +3 cation to not receive significant lattice distortions. Furthermore, the uranium cationic lattice stays consistently as U +4 .
