Degradation of First Wall Materials under ITER Relevant Loading Conditions

Nuclear fusion seems a promising alternative energy source. This PhD thesis investigates the various degradations that the first wall (Be, W) may experience during ITER-relevant loading conditions. The thermal loadings were simulated with an electron beam. The degradation that occurs (roughening, crack initiation, propagation, melting …) was investigated by microstructural tools. To understand why and how this damage occurs, various mechanical properties were investigated on W-based materials up to temperatures of 2000°C. The observed thermal shock cracking mechanisms could be related to a number of properties analysed in this PhD and are supported by a theoretical background. To understand their degradation under neutron exposure, the thermal resistance of both Be as W materials were investigated after irradiation in the BR2 reactor. Finally, to complete the assessment of the analysed materials, research related to fuel retention (radio-active tritium) was needed as well. However, no system exists that is capable to investigate the synergistic effects of tritium and neutrons on the retention characteristics. For this purpose, a new and unique plasma simulator (VISIONI) was initiated, set-up and followed-up during this PhD work, with the aim of extending our understanding of materials behaviour under ITER relevant fusion conditions.