Small and medium reactors using lead alloys as coolant are one of the promising reactor concepts with improved safety because of their thermal-physical and chemical properties. This paper focuses on development of Al-alloy coating for nuclear systems using liquid lead-bismuth eutectic (LBE). Since corrosion attack becomes severe against structural steels at high temperatures in liquid LBE, it is necessary to improve corrosion resistance of steels. An Al-alloy coating method using Al, Ti and Fe powders, and laser beam heating has been developed. Main defects formed in an Al-powder-alloy coating process are surface defects and cracks. Conditions required to avoid these defects are employment of the laser beam scanning rate of 20 mm/min and adjustment of the Al concentration in the coating layer. According to results of the corrosion tests at 550°C in liquid LBE, the Al-alloy coating layers on 316SS protect severe corrosion attack such as grain boundary corrosion and LBE penetration observed in 316SS without coating. The good corrosion resistance of the Al-alloy coating is based on the thin Al-oxide film which can be regenerated in liquid LBE. From the viewpoints of the soundness of produced Al-powder-alloy coating layers and preservation of their corrosion resistance, it is estimated that the range of the adequate Al concentration in the coating layer is from 4 to 12 wt%.

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