Characteristics of iron and nickel diffusion in molten lead-bismuth eutectic

The characteristics of iron (Fe) and nickel (Ni) diffusion in molten lead bismuth eutectic (LBE) were investigated experimentally by using capillary method. The diffusion coefficients of iron (Fe) and nickel (Ni) were determined from measured axial concentration distributions of Fe and Ni in LBE specimens. The correlation of the diffusion coefficients can be obtained as D-Fe =3.5x 10(-3)exp (-4.15 x10(-4)/RD ( 550 degrees C <= T <= 650 degrees C) [cm(2)/s], D-Ni = 1.7x10(-3)exp (-3.63 x10(-4)/RD (500 degrees C <= T <= 650 degrees C) [cm(2)/s]. The diffusion coefficient of Fe in LBE obtained is approximately the same as the result derived by Balboud Celerier. The result of the diffusion coefficient of Ni is almost the same order of magnitude as that of Fe, in spite of much higher solubility of Ni than that of Fe in LBE. From microstructure observation by using the scanning electron microscope (SEM) and the energy dispersive X-ray spectroscopy (EDX), it is found that in case of Ni diffusion, some compounds composing 50-60% Ni, 15-20% Pb and 15%-20% Bi, were observed in the solid specimen. It is estimated that the formation of the compounds slowed down the diffusion of Ni into LBE.