Nanofluid alumina-water system (g-Al 2 O 3 ) and water are used as a quenching medium in simulation of loss of coolant accidents (LOCAs). Zircaloy-4 (Zr-4) fuel cladding was used in this experimental. Zircalloy-4 was heat treated in various temperature (1000 to 1250 C) at 1 h then quenched in alumina-water nanofluid and water. After quenching, the mass gain of Zr-4 fuel cladding was observed as the function of heat treatment. Optical microscope and XRD and are used to identify the Zr-4 fuel cladding after heat treated. Optical microscope characterization shows that alumina-water nanofluid effective reduced the cracks on surface of the Zr-4 fuel cladding at temperature up to 1200 °C. X-Ray diffraction (XRD) analysis shows that the oxide scale ZrO 2 formed on the surface of Zr-4. This study demonstrated the effect on nanofluid alumina-water system to reduce oxidation of Zr-4 fuel cladding. Lower oxidation of Zr-4 fuel cladding in nanofluid alumina-water system has been obtained compared to water.