INTERDIFFUSION BETWEEN U-ZR FUEL VS SELECTED CLADDING STEELS

To better understand fuel-cladding compatibility issues as affected by diffusion processes in Argonne National Laboratory's Integral Fast Reactors, interdiffusion studies were carried out with solid-solid diffusion couples assembled with a U-23 at. pct Zr alloy and cladding steels, such as 316, D9, and HT9. All diffusion couples were annealed at 700-degrees-C and examined metallographically and by scanning electron microscopy-energy-dispersive spectroscopy analysis for diffusion structure development. The development of diffusion layers in the couples for various cladding steels is compared and discussed in light of the relative diffusion behavior of the individual elements, intermetallic formation, and experimental diffusion paths. In the context of fuel-cladding compatibility, HT9 is considered superior to 316 and D9, as it develops the smallest diffusion zone with the fewest number of phases.