One of the major R&D focuses in the European fusion power plant (DEMO) program is to establish a physical as well as technological basis for reliable power exhaust during normal and off-normal operational scenarios. In this regard, the most crucial engineering challenge is to develop robust high-heat-flux components (such as divertor targets) being capable of withstanding extreme thermal loads up to 20MW/m2 with a sufficient heat removal capacity and structural reliability. Moreover, to maintain structural integrity and reliability under intense fast neutron irradiation and to ensure sufficient lifetime against armor erosion and cooling pipe corrosion are further critical requirements. In the framework of EUROfusion DEMO divertor project (WPDIV), integrated R&D efforts have been conducted to develop advanced design concepts and related key technologies for the divertor targets. Emphasis is placed on the experimental demonstration of envisaged high-heat-flux fatigue performance of the novel design concepts using small scale mock-ups. To this end, dedicated test mock-ups were manufactured on the basis of extensive design studies, non-destructive inspection techniques were employed to detect defects included during production, high-heat-flux fatigue tests were conducted by means of neutral beam irradiation and microscopic post-examination was carried out for damage characterization. Finally, FEM-based failure modelling was performed to support the interpretation of damage and failure features observed in the mock-up testing.
In this contribution, a brief overview is presented on the major engineering issues and R&D activities for the high-heat-flux components of fusion reactors, defect inspection methodology and the selected results of the latest high-heat-flux test campaign.