Papers by Keyword: Nuclear Fusion

Abstract: One of the biggest challenges that the world faces is definitely the need for more energy. As the world’s fossil fuel supplies dwindle down, it becomes more and more important to find clean sources of energy that can also fulfill the global demand for more energy. Fortunately, aerospace technology can be of use, as the moon can be used to harvest ³He, which can be a clean source of nuclear fuel for fusion reaction on Earth, as well as on the moon. This paper will demonstrate that the concept of moon mining needs to be explored further as ³He can be of great use for solving the world’s energy needs.

Abstract: Refractory materials, in particular tungsten base materials are considered as primary candidates for structural high heat load applications in future nuclear fusion power plants. Promising helium-cooled divertor design outlines make use of their high heat conductivity and strength. The upper operating temperature limit is mainly defined by the onset of recrystallization but also by loss of creep strength. The lower operating temperature range is restricted by the use of steel parts for the in- and outlets as well as for the back-bone. Therefore, the most critical issue of tungsten materials in connection with structural divertor applications is the ductile-to-brittle transition. Another problem consists in the fact that especially refractory alloys show a strong correlation between microstructure and their manufacturing history. Since physical and mechanical properties are influenced by the underlying microstructure, refractory alloys can behave quite different, even if their chemical composition is the same. Therefore, creep and thermal conductivity have been investigated using typical commercial tungsten materials. Moreover, the fracture behavior of different tungsten based semi-finished products was characterized by standard Charpy tests which have been performed up to 1100 °C in vacuum. Due to their fabrication history (powder mixing, pressing, sintering, rolling, forging, or swaging) these materials have specific microstructures which lead different fracture modes. The influence of the microstructure characteristics like grain size, anisotropy, texture, or chemical composition has been studied.

Abstract: In the development of nuclear fusion into a future peaceful energy source, the scheme of magnetically confined fusion plasmas has experienced substantial progress in the last decades. Some of the main remaining materials issues are the high heat loads and the erosion of plasmafacing components by erosion from particle impact. Since component lifetime considerations and the negative influence of impurities on the plasma lead to opposite conclusions about the materials choice, an experimental investigation of the applicability of tungsten as plasma-facing material is currently performed at the tokamak fusion experiment ASDEX Upgrade in Garching, Germany. For this purpose an industrial scale method to coat graphite tiles with tungsten thin films was required. Therefore a comparative study of the heat load behaviour of coatings deposited with various PVD techniques was performed. Tungsten coatings on graphites and fiber reinforced carbons were investigated with respect to their properties relevant for fusion research including electron-beam loading with heat loads exceeding 20MW/m2.