Diffusion of Cerium in Uranium-Zirconium Solid Solutions

抄録

Two types of diffusion couples, U–23 mol%Zr with U–23 mol%Zr–1.3 mol%Ce and U–95 mol%Zr with U–23 mol%Zr–1.3 mol%Ce, were annealed isothermally at 1123 K and 1023 K in order to provide basic data on Ce diffusion in U–Zr alloys, which are the fuel forms for advanced nuclear reactors. Because the Ce solubility in the U–23 mol%Zr alloy is less than 1 mol% in this temperature range, Ce-rich precipitates were formed and dispersed in the U–23 mol%Zr–1.3 mol%Ce alloy. The concentration profiles of Ce in the U–23 mol%Zr/U–23 mol%Zr–1.3 mol%Ce couples were analyzed based on the theoretical solutions of the one-dimensional diffusion equation for the semi-infinite diffusion couple, either side of which is supersaturated with the diffusing substance. From this analysis, the diffusion coefficients of Ce in the U–23 mol%Zr solid solution (γ–U, β–Zr) were estimated to be ∼2×10⁻¹³ m²/s at 1123 K and ∼6×10⁻¹⁴ m²/s at 1023 K, which are between the values extrapolated from the reported self-diffusion coefficients of γ–U and β–Zr. In the U–95 mol%Zr/U–23 mol%Zr–1.3 mol%Ce couples annealed at 1123 K and 1023 K, the concentration profiles showed up-hill diffusion of Ce. The interdiffusion coefficients in this quasi-binary U–Zr system containing Ce were obtained from the U or Zr concentration profile and compared with the reported interdiffusion coefficients in the binary U–Zr system without Ce. The result indicated that Ce does not have significant influence on interdiffusion in the U–Zr solid solutions.