Division of Structural Materials (FWIK)
The pressure vessel of a nuclear reactor (RPV) is of utmost importance to safety. The RPV steels are subject to operational loads, including those resulting from the radiation field generated by nuclear fission. Neutron irradiation leads to detrimental changes in macroscopic mechanical properties i.e. increases in yield strength and reductions in fracture toughness. This radiation embrittlement – or radiation induced ageing - is a multiscale phenomenon as illustrated in the figure.
HZDR contributes to the intense worldwide efforts to detect irradiation damage early, to understand the underlying phenomena, to develop appropriate numerical models and to evaluate the implications for the RPV integrity. The focus is put on the elucidation of the formation mechanisms of radiation defects on the nanometer scale and their effects on mechanical properties. This work is supported by the H2020 project SOTERIA.
Another focus is directed to candidate materials for advanced reactor concepts as well as fusion reactors. These materials will be exposed to significantly higher operation temperatures and higher doses of neutron irradiation. Fe-Cr alloys and their oxide dispersion strengthened versions promise excellent creep strength and radiation stability. A fabrication route based on mechanical alloying and spark plasma sintering was established. Ion irradiation is used to mimic neutrons and to study the radiation stability. The characterisation and post-irradiation examination is done by means of complementary microstructural techniques. Atomistic modelling helps to explore the underlying mechanisms at the nm-scale. This work is supported by the FP7 project MATISSE.
- Fracture mechanics testing of irradiated materials in hot cells
- Characterisation of the irradiated nanostructure by small angle neutron scattering experiments (SANS) and other structural analysis methods (TEM, PAS, APT)
- Atomic scale simulations (e.g. Ab initio, Molecular Dynamics, Monte Carlo Simulation)
The atomistic simulations are used to study fundamental atomic-level dynamics, kinetics and thermodynamics in solids under particle irradiation and/or thermal and mechanical load with special emphasis on the properties of defects, foreign atoms, nanoclusters and interfaces. Research topics are e.g. ion-beam induced defect formation, defect migration, interaction of defects with foreign atoms, properties of nanoclusters in iron-based alloys, ion-beam-mixing of semiconductor heterostructures, solid-phase epitaxial recrystallization of amorphous Si and Ge, and nanotribology of carbon-based coatings.