Dr. Nabil Daghbouj, Ph.D.

Accident Tolerant Fuel (ATF) concepts aim to enhance the safety and performance of nuclear fuel, particularly under accident conditions. Conventional zirconium (Zr) alloy claddings suffer from rapid high-temperature oxidation, which limits their performance in severe accident scenarios. ATF coatings such as chromium (Cr) and silicon-carbide fiber-reinforced silicon carbide (SiCf/SiC) have been developed to improve oxidation and corrosion resistance and to modify fission-product transport and retention behavior. This doctoral project investigates the interaction between ATF coatings and fission products, focusing on diffusion behavior, chemical stability, interface reactions, and mitigation of fuel–cladding chemical interactions. In parallel, the response of coated Zr alloys to irradiation conditions representative of neutron exposure will be studied, including defect formation, radiation-induced phase transformations, and mechanical stability. The feasibility of the project is ensured by well-established experimental approaches and access to dedicated irradiation and characterization facilities. Irradiation and Fission-Product Exposure Strategy Neutron-irradiation effects will be simulated using ion irradiation in collaboration with European ion-beam facilities (https://www.ionbeamcenters.eu/ion-beam-facilities/). Proton (H⁺) irradiation will be used to mimic hydrogen uptake, while heavy-ion irradiation will reproduce displacement damage. Fission-product exposure will be achieved through controlled ion implantation of surrogate species (e.g., Cs, Sr, Ag, Xe), enabling systematic investigation of fission-product diffusion, trapping, and interaction with coating–substrate interfaces. Characterization Methods in the Czech Technical University in Prague and CEITEC Brno The candidate will perform comprehensive, hands-on characterization using state-of-the-art techniques, including: • X-ray diffraction (XRD): phase identification, residual stress, irradiation-induced lattice changes • Scanning electron microscopy (SEM) with EDS: microstructure, morphology, and chemical mapping • Atomic force microscopy (AFM): surface morphology and roughness evolution • Focused ion beam (FIB): site-specific sample and TEM lamella preparation • Transmission electron microscopy (TEM/STEM): nanoscale defects, interfaces, and fission-product clusters • Electron backscatter diffraction (EBSD): grain structure, texture, and deformation mapping • Transmission Kikuchi diffraction (TKD): high-resolution crystallographic analysis in thin lamellae This structured experimental framework ensures that the project is technically feasible and scientifically rigorous. The outcomes will provide fundamental insight into the behavior of ATF coatings under irradiation and in the presence of fission products, directly supporting the development of safer and more reliable nuclear fuel cladding systems

The development of advanced materials for nuclear fusion reactors is essential for achieving sustainable fusion energy. Plasma-facing materials (PFMs), which operate under extreme thermal loads and intense particle fluxes, must tolerate high-energy neutron irradiation as well as plasma-induced helium (He) and hydrogen (H) implantation. Refractory high-entropy alloys (RHEAs), composed of multiple principal elements, exhibit high mechanical strength, thermal stability, and resistance to extreme environments, making them promising candidates for next-generation fusion applications. This doctoral project will systematically investigate the ion-irradiation resistance and corrosion behavior of RHEAs over a wide temperature range. The study will focus on the influence of grain size, chemical ordering, diffusion mechanisms, and alloy composition on radiation damage tolerance and environmental stability. The research is designed using established experimental methods and access to specialized irradiation and characterization facilities, ensuring technical feasibility. Material Synthesis and Irradiation Strategy RHEA thin films will be synthesized by magnetron sputtering, allowing precise control over composition, thickness, and microstructure. Irradiation experiments will be performed in collaboration with established European ion-beam facilities (https://www.ionbeamcenters.eu/ion-beam-facilities/). Helium (He⁺) and hydrogen (H⁺) ion irradiation will be used to simulate plasma-induced implantation effects, while heavy-ion irradiation will reproduce displacement damage representative of neutron irradiation in fusion environments. Irradiations will be conducted at controlled temperatures to study defect evolution, diffusion processes, and radiation-induced microstructural changes. Characterization Methods in the Czech Technical University and CEITEC Brno The PhD candidate will carry out comprehensive, hands-on characterization using state-of-the-art techniques, including: • X-ray diffraction (XRD): phase stability, lattice distortion, and irradiation-induced structural changes • Atomic force microscopy (AFM): surface morphology and roughness evolution • Scanning electron microscopy (SEM) with EDS: microstructure and elemental distribution • Focused ion beam (FIB): site-specific sample and TEM lamella preparation • Transmission electron microscopy (TEM/STEM): nanoscale defect structures, irradiation-induced damage, and gas-bubble formation • Electron backscatter diffraction (EBSD): grain size, texture, and orientation mapping • Transmission Kikuchi diffraction (TKD): high-resolution crystallographic analysis in thin films Positron annihilation spectroscopy will be performed in collaboration with Helmholtz-Zentrum Dresden-Rossendorf, enabling quantitative analysis of vacancy-type defects and irradiation-induced defect populations. Expected Outcomes This integrated experimental approach will provide a detailed understanding of how RHEAs respond to irradiation and corrosive environments, and how microstructural and compositional parameters govern their performance. The results will guide the design of optimized RHEAs with enhanced irradiation tolerance and corrosion resistance, contributing directly to the development of safer, more durable plasma-facing materials for future fusion reactors.