Abstract
Plasma sprayed zirconium (Zr) metal coatings onto uranium-molybdenum (U-Mo) alloy nuclear reactor fuel foils act as a diffusion barrier between the fuel and the aluminum fuel cladding. Neutron diffraction was performed to investigate the crystallographic phase composition, crystal orientations and lattice parameters of the plasma sprayed Zr and the U-Mo substrate. The neutron diffraction results show that the plasma sprayed Zr coating is crystalline, phase pure (alpha-Zr) and has preferred crystalline orientation likely due to directional solidification. Also, there is a slight (~0.01 Å for a direction and ~0.016 Å for c direction) increase in the plasma sprayed Zr lattice parameter indicating oxygen in the lattice and some residual thermo-mechanical strain. There is little or no modification of the underlying U-Mo following plasma spraying. In particular, there is no detectable allotropic transformation of the starting gamma-U (body-centered cubic) to alpha-U (orthorhombic). The unique neutron diffraction capabilities at LANL are well suited for nuclear fuel characterization offering distinct advantages over conventional X-ray diffraction and destructive metallography.
