| To develop the advanced zirconium alloy for nuclear fuel cladding, the corrosion behaviors of Zr-X (X=Nb, Cu) binary alloys were investigated. Microstructures were observed by using optical microscopy and transmission electron microscopy(TEM). The corrosion tests were performed in three different conditions, water at 360℃, 70 ppm LiOH at 360℃ and steam at 400℃ for 100 days. In addition, the oxide crystal structure was characterized by low angle diffraction method of X-ray. The grain sizes of Zr-based binary alloys were gradually decreased with alloying additions, while the size and number of precipitates were increased. The corrosion resistance of both Zr-xNb and Zr-xCu alloys was decreased with alloying additions. Zr-xCu alloy showed higher corrosion rate than Zr-xNb alloy in LiOH solution. Both alloys had less amounts of tetra-ZrO₂ phases in oxide with alloying additions. It was considered that the increase of corrosion rate with Nb and Cu addition would be resulted from the early transition of oxide structure from protective tetra-ZrO₂ to non-protective mono-ZrO₂. |
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