We, for the first time, observe ZrO8 complex in Zr-doped UO2, which is a corium structure, using experimental characterization integrated with first-principle computational validation. Atomic level structure of U1-yZryO2 pellets (y = 0.01, 0.03, 0.05, and 0.1) is identified using Raman spectroscopy measurement and X-ray diffraction pattern analysis. The lattice constants shrink with increasing Zr doping levels, which consistently represents in the positive shift of T-2g Raman vibration peak around 445 cm(-1). More interestingly, conventionally unknown new Raman peak appears around 598 cm(-1), which has not been observed in neither a pure ZrO2 nor UO2 doped with tetravalent elements other than Zr. We unveil that the new peak originates from ZrO8-type complex formed on the fluorite UO2. Our study provides precise understanding on the formation mechanisms and material properties of the corium in the hypervalent oxide.