Implementation and validation of a resuspension model in MELCOR 1.8.6 for fusion applications

In a fusion reactor, a continuous erosion of the Plasma Facing Surfaces (PFSs) occurs during normal plant operations. This erosion creates a particles debris (dust) spanning from 1 μm to 50 μm in dimension. These formed dust deposits on the bottom of the Vacuum Vessel (VV), i.e. on the divertor surface. In case of Beyond Design Basis Accident (BDBA), this dust may be mobilized and transported towards the confinement building, or even into the outer environment. Therefore, the evaluation of the maximum mobilized dust mass is a safety issue of main concern, because it may pose a radiological risk to plant operators and to the outer population. To investigate these incidental scenarios, lumped-parameters codes such MELCOR are commonly employed. A specific version of MELCOR, capable to treat the phenomena occurring in a fusion reactor, is developed by Idaho National Laboratory (INL). Although, a model to treat the mobilization of dust is still not yet implemented in this specific MELCOR version. This paper presents, after a review of the available resuspension models, the selection of a specific resuspension model and the efforts made for its validation against different experimental tests. The selected model is the semi-empirical “Force Balance” model, just implemented in the ASTEC and ECART codes, but specific modifications were introduced to allow its implementation in MELCOR through ad hoc developed Control Functions (CFs). Its validation shows a quite good agreement with most of the experimental tests investigated, highlighting its capabilities for the safety analysis of the forthcoming fusion reactors.