Dust mobilization experiments in the context of the fusion plants—STARDUST facility

This paper deals with the dust mobilization in fusion facilities, in which the plasma disruptions induce an erosion of small particles causing external releases if accidents occur. In the ITER safety guidelines the administrative limits of 200 kg carbon, 100 kg beryllium and 100 kg tungsten inside the VV have been fixed to avoid the population evacuation in case of accident. The conservative assumption to mobilize all these dusts is adopted in the accident analyses. To support a less conservative hypothesis some experiments have been performed inside the STARDUST facility (ENEA Frascati laboratories, Italy). The ECART code has been used for blind simulations to validate the dust transport model implemented. The results match satisfactorily the experiments. The dusts used were carbon, stainless steel, tungsten and a mixed dust (C, SS, W). The experiments represent a LOVA due to a small or a large air leak through two different VV ports. The measured mobilization rate ranges from 0.03% to 100% of the total amount of dust. That means the mobilization is strongly dependent on the relative position between air inlet and dust location and that the dust mobilization assumptions in the accident analyses shall be reduced, in some cases of several factors.