Characterization of irradiation damage using x-ray diffraction line-profile analysis

During operation, structural components made of zirconium alloys are subject to neutron irradiation, which leads to the displacement of zirconium atoms from their lattice sites, the production of self-interstitials and vacancies, and eventually dislocation loops. This process can lead to deleterious effects such as irradiation growth, creep, and embrittlement as well as accelerated aqueous corrosion. Quantitative analysis of dislocation line densities is seen as an important pathway for distinguishing between the irradiation response of different alloys. The analysis of irradiation damage using X-ray diffraction (XRD) line-profile analysis has proven to be a powerful complementary technique to transmission electron microscopy, which samples a comparatively large volume and is less affected by the subjectivity of image analysis. In this paper we present and analyze three different types of XRD experiments, describing their purpose and the new insight achieved using each technique. First, we present work carried out on neutron-irradiated samples, comparing dislocation line densities measured by XRD with macroscopic growth measurements. A second experiment using a synchrotron-based X-ray microbeam enabled the mapping of dislocation line densities as a function of depth from the surface of proton-irradiated zirconium alloys. These data are compared with calculated damage profiles, providing new insight into the early saturation of damage. Finally, the last example presented here focuses on synchrotron-based 3D XRD measurements, for which dislocation-loop line densities were analyzed in hundreds of individual grains, providing excellent statistics about the grain-to-grain variability of line densities.