Strain and defects in irradiated materials : a study using X-ray diffraction and diffuse scattering

Overview & Synopsis

Ion beams are commonly used in the framework of nuclear materials in order to reproduce, in a controlled way, the different sources of irradiation that these materials are submitted to. The interaction of ions with the material induces the formation of crystalline defects along the path of these ions,associated with high strains in the irradiated region. One of the main issues of the electro-nuclearindustry is the encapsulation of the long-term nuclear waste. Yttria stabilized zirconia (YSZ) is one of the materials that can be used as an inert matrix for the transmutation of actinides and therefore,understanding its behaviour under different conditions of irradiation is of utmost importance.This thesis is divided into two distinct parts. In the first part of this work, we have used advanced X-raydiffraction (XRD) techniques in order to characterize the strain and the damage levels within the irradiated region of the crystals. The strain and the damage profiles were modelled using B-splines functions and the XRD data were simulated using the dynamical theory of diffraction combined with a generalized simulated annealing algorithm. This approach was used to study YSZ single crystals irradiated with Au 2+ ions in a wide range of temperatures and fluences. The results were compared with the RBS/C results obtained for same samples.The second part of the thesis is devoted to the development of a specific model for calculating the two-dimensional XRD intensity from irradiated single crystals with realistic dimensions and defectdistributions. In order to achieve this goal, we have implemented high-performance parallel computing (both multi-processing and GPU-based) to accelerate the calculations. The approach was used to successfully model the reciprocal space maps of the YSZ single crystals which exhibit a complex defect structure.