Analysis of constituent redistribution in the gamma (bcc) U-Pu-Zr alloys under gradients of temperature and concentrations

Rods of a ternary alloy (71U-19Pu-10Zr by weight percent) were annealed und er a temperature gradient of 220 degrees C/ cm for 41 days and examined for micro-structural development and compositional redistribution. An enrichme nt of Zr with concurrent depletion of U was observed within the gamma (bcc) phase region on the hot-end side (T congruent to 740 degrees C). The exper imental redistribution of the elements in the gamma (bcc) phase was analyze d in the framework of multicomponent mass transport with due consideration of thermotransport and ternary diffusional interactions. Based on a new ana lysis involving an integration of interdiffusion fluxes in the diffusion zo ne, kinetic parameters related to the thermotransport and ternary interdiff usion were calculated for each component i over selected ranges of composit ion. The thermotransport coefficients of U, Pu, and Zr were in the approxim ate ratio of 1:2:-4.5 in the hot-end region. In addition, the interdiffusio n flux contributions arising from the gradients of temperature and concentr ations of U and Zr were estimated. (C) 2000 Elsevier Science B.V. All right s reserved.