[en] The wastage effects of a sodium-water reaction resulting from a small leak in a liquid-metal fast breeder reactor steam generator were investigated. These experiments were conducted at low steam injection rates, ranging from 0.07 to 13.8 g/s, with the following test conditions: sodium temperature 480⁰C, sodium velocity 0.24 m/s, and target material 2¹/₄ Cr--1 Mo steel. Employed were nozzle diameters (D) from 0.2 to 1.5 mm, nozzle-to-target distances (L) from 5 to 100 mm, and L/D ratios from 7.14 to 400. An empirical equation of wastage rate of 2¹/₄ Cr--1 Mo steel was obtained, including parameters of sodium temperature, steam injection rate, and nozzle-to-target distance. The depth curves and the widths of the area affected by wastage were examined. These test results were applied to the safety considerations for the prototype steam generators in Japan