Wall Forum 2023

The reduced activation ferritc martensitic steel EUROFER is one of the foreseen structural materials for future fusion reactors. The exposure to energetic fusion neutrons will generate displacement damage in the steel which acts as trapping sites for hydrogen isotopes (HIs). For predictive simulations of HI retention the concentration of the trap sites and HI trap-binding energies are needed. In this work the potential influence of HIs present during displacement damage on the resulting trap site concentration is investigated. The results suggest that the presence of D and He in EUROFER will result in increased retention compared to pure EUROFER under displacement damage [mehr]

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We developed a novel, recently patented application of hydrogenography, i.e., the change of the optical properties of certain indicator materials (e.g., yttrium) when these are charged with hydrogen isotopes. By applying patterned, discontinuous yttrium films to the back side of permeation samples, we circumvented the issue that the hydrogen isotopes could also diffuse laterally within the yttrium film, which might blur or even prevent detection of laterally inhomogeneous diffusion effects through the actual sample. Thus, we were able to directly visualize the preferential permeation of deuterium along grain boundaries in recrystallized tungsten foils exposed to a low-temperature deuterium plasma. Similarly, we were able to show that permeation of deuterium focuses on the percolating Fe-Ni matrix phase of the tungsten heavy alloy HPM 1850. [mehr]

This presentation will introduce the work being conducted in the non-metallics team at UKAEA, with a focus on silicon carbide composites and multifunctional coatings. There will also be an introduction to future work in the non-metallics team around SiC composite manufacturing, radiation shielding, and radiation-resistant electronic devices.SiC composites are a candidate structural material being considered for future fusion power plant designs, owing to their high temperature capability enabling more versatile energy production as well as stability under high dose neutron irradiation. Topics will cover a range of length-scales from atomistic modelling of defects including interactions of point defects and transmutation products, micromechanical testing, and TEM of radiation effects in SiC fibres and SiC matrix. Multifunctional coatings are required in regions such as the breeder blanket and tritium extraction system to reduce permeation of tritium while also resisting liquid metal corrosion. Ceramic oxides such as erbia are good candidates for permeation barriers while refractory metals such as tungsten show promising resistance to liquid metal corrosion. This presentation will discuss hydrogen retention and irradiation performance of a range of ceramic and metallic coating materials. [mehr]

For tungsten in divertor parts of future fusion reactors, a fine-grained microstructure is preferred to reduce its brittle-to-ductile transition temperature and minimize cracking due to cyclic thermal and mechanical loading. Our ongoing study on warm- and cold-rolled tungsten sheets with different degrees of deformation explores the potential of potassium-doping (K-doping) to stabilize the microstructure at high operation temperatures. Successful production of technically pure and K-doped tungsten sheets rolled equivalently up to very high logarithmic strains of 4.6 was proven accompanied by in-depth analysis of the evolution of microstructure and mechanical properties after the different rolling steps in past publications. The current investigation on the same material batch analyses and discusses the distribution of K-bubbles with increasing rolling strain, their chemical composition by means of advanced nano-scaled EDX analysis, and their influence on microstructural changes of tungsten due to recovery, recrystallization and grain growth in different temperature regimes between 600 °C and 2400 °C. [mehr]