Determination of dislocation density and composition of β-Zr in Zr–2.5Nb pressure tubes using X-ray and TEM

The dislocation density and the composition of the β-Zr phase were determined using an X-ray diffractometer and TEM in an off-cut of the Zr–2.5Nb pressure tube irradiated in Wolsong Unit 1. Through Fourier analysis of diffraction line profiles of {1 1 2̄ 0}, {1 0 1̄ 0} and {0 0 0 1} planes, an X-ray method determined the coherent block size and the lattice strain energy, from which the a- and c-type dislocation densities were evaluated assuming that the screw dislocation only contributes to the lattice strain energy. This X-ray method was demonstrated to reliably determine the a- and c-type dislocation densities in the Zr–2.5Nb tube which agreed well with the independently measured values for the same Zr–2.5Nb tube using the AECL’s own method. For the first time, we developed a procedure to determine distributions of a- and c-type dislocation densities from distributions of the line broadening of the basal planes and the prism planes. Through this procedure, the volume-averaged c- and a-type dislocation densities in the Zr–2.5Nb were determined to be 2.69×1014 m−2 and 0.97×1014 m−2, respectively, which agree very well with those analyzed by TEM. The Nb content of the β-Zr phase was determined using an X-ray from a change in the lattice distance of the {1 0 0} planes, which agrees well with that by the electron diffraction spectroscopy analysis on the extracted β-Zr particles.