URANIUM PLUTONIUM INTERDIFFUSION AT 750-DEGREES-C

An isothermal diffusion couple between pure uranium and a uranium-27 at% plutonium alloy was annealed at 750-degrees-C for 25 h. Composition profiles were determined from electron microanalyses, from which interdiffusion fluxes and interdiffusion coefficients were evaluated. The presence of plutonium greatly increases diffusion at this temperature over what would be predicted from uranium self-diffusion studies. Moreover, diffusivities in the body centered cubic U(gamma) phase increase with increasing plutonium concentration, unlike interdiffusion in the orthorhombic U(alpha) phase at lower temperatures. The diffusion results suggest that plutonium has a greater intrinsic diffusivity than uranium at 750-degrees-C.