Tore Supra carbon dust resuspension studies

Abstract Understanding the mobilization of dust in tokamaks is essential for proper machine operation and occupational worker exposure during maintenance operations. It is also a key issue for the safety assessment of ITER in Loss of Vacuum Accident (LOVA) scenario. Dust mobilization by airflow is strongly dependent on particle size and shape, and these characteristics are related to the specific process of erosion of the plasma facing components. Accordingly, it is important to develop techniques for in situ analysis of wall dustiness and potential dust mobilization by airflow. We propose a device, called DUSTER BOX, allowing to study dustiness of Tore Supra surfaces and to collect dust sample without mechanical stresses. This device consists in a simple airflow channel box and allows injecting a filtered airflow tangentially to the surface. The flow velocity parallel to the plasma facing components is 10 m/s and the friction velocity is 0.7 m/s which is the value needed to tear off particles greater than few microns from surfaces. After being resuspended, carbon dusts are collected on a membrane filter for weight analysis, size distribution analysis and electron microscope imaging. DUSTER BOX has been successfully used to realize a mapping of particles deposit in Tore Supra and to collect samples for size distribution analysis.