Erosion of divertor tungsten armor after many ELMs

B. Bazylev¹, G.Janeschitz², I. Landman², S. Pestchanyi³

¹Luikov Heat and Mass Transfer Institute, 220072, Minsk, Belarus

²Forschungszentrum Karismhe, P.O. Box 3640. 76021 Karlsruhe, Germany

³Troitsk Institute for Innovation and Fusion Research, 142092 Troitsk, Russia

During the instability of Edge Localized Mode (ELM), a part of confined plasma is dumped at the tokamak divertor armor, which may result in a pre-surface melting of metallic plates. Melt motion in the thin layer may produce surface roughness and droplet splashing thus causing erosion of the target. During one ITER discharge, about 10³ ELMs are expected. The position of separatrix strike point (SSP) at the divertor plate can vary from one ELM to another, which correspondingly changes the distribution of the heat flux and the pressure of impacting plasma.

For the divertor tungsten armor, the results of fluid dynamics simulation of the melt motion erosion after repetitive stochastically varying plasma heat loads of many ELMs with typical energy density deposition of 1-3 MJ/m² and duration of 0.1-0.5 ms are presented. For different single ELMs, the heat loads at the target are calculated by the two-dimensional MHD code FOREV-2 with detailed radiation transport. The target erosion is calculated by the one-dimensional fluid dynamics code MEMOS in the ‘shallow water’ approximation, with the surface tension- and viscosity of molten metal as well as with the Lorentz forces due to the currents crossing the melt layer.