The inner wall of future fusion reactors is subjected to extreme heat flux densities comparable to those on the outer wall of space ships when they enter the earth’s atmosphere again. In addition, there are intensive particle and neutron fluxes which lead to material erosion and defects. Among other things, because of its high melting point, tungsten is regarded as the preferred wall material. However, its brittleness and the high oxidation rate in the event of an extraordinary air intake at high temperatures are problematic. The scientists at Jülich Research Center, together with national and international partners, have developed new, smart material concepts based on tungsten: fiber-reinforced composites, which reduce the spread of harmful cracks, as well as smart alloys of tungsten, chromium and the light metal yttrium W-Cr-Y), which show an approximately 100,000-fold reduced oxidation rate compared to pure tungsten.
After successful development, characterization and production of material samples, research on smart tungsten materials has now entered a second, decisive phase – the qualification of materials under fusion-type stress scenarios. These are carried out at the Forschungszentrum Jülich at special test facilities: electron beam systems for thermal melt tests as well as linear plasma systems and laser systems for combined particle and thermal stress. First measurements on material samples in the PSI-2 linear plasma system with thin layers of W-Cr-Y have shown that the tungsten alloy is similarly resistant to material erosion compared to pure tungsten reference samples. The initial reduction in the oxidation capacity is also retained after plasma loading. This demonstrates the basic suitability of the smart alloy for use in fusion systems.
A next, important step towards the development of a smart wall concept for the fusion reactor has already been done: research partners at the Belgian institute SCK-CEN in Mol have begun to investigate the emission of tungsten with neutrons by means of a European research project. In approximately one and a half years, new stress tests can then be carried out at the Jülich Research Center on the newly produced material samples produced in this way.
A. Katz, A. Katzer, A. Katzer, A. Katzer, A. Katzer, A. Katzer, A. Katzel, and others N. Orda
Smart alloys for a future FusionPowerSystem: First studies underneathPlastic load and in accidental conditions
Nuclear Materials and Energy (2016), DOI: 10.1016 / j.nme.2016.11.015
Source : Forschungszentrum Jülich