Implementation and validation of a particle resuspension model in a CFD code – Application to an air ingress scenario in a vacuum toroidal vessel

Abstract

International audienceDuring a loss of vacuum accident (LOVA), dusts that will be present in the future tokamak ITER are likely to be re-suspended, inducing a risk for explosion and airborne contamination. Evaluating the particle resuspension in case of a LOVA is therefore a major issue and it can be investigated by using a CFD code. To this end, this article presents the implementation of a resuspension model in a CFD code (ANSYS CFX), its validation with experimental tests conducted by IRSN and lastly its application to an air ingress in a vacuum toroidal vessel with a volume comparable to ITER one.In the first part of the article, the implementation of the Rock’n’Roll model in ANSYS CFX for constant friction velocities and its adaptation to non-constant friction velocities will be detailed. This model, developed by Reeks and Hall [1], describes the kinetics of resuspension phenomenon by taking into account the equilibrium between the different forces acting on the particle deposited on a rough wall, such as the airflow forces and the adhesive forces. The second part of the article will be devoted to the validation of the model implementation. As one of the key parameters in the resuspension phenomenon is the friction velocity, CFD simulations will be compared to experimental resuspension tests from IRSN, on the BISE facility used by Peillon et al. [2] for the steady state case and on a dedicated facility for the transient case, allowing to validate both forms of the Rock’n’Roll model. Finally, the paper presents the simulations obtained on the particle resuspension for an air ingress scenario in a large vacuum vessel for which friction velocity field was already studied by Gelain et al. [3]. This case is particularly complex because the initial pressure is close to the vacuum, so the particle behaviour is different from that at atmospheric pressure. Further, a competition between airflow forces and gravitational force occurs, due to the vacuum, potentially restricting the resuspension, and the pressure influence also has to be taken into account in the particle transport and deposition [4].Three particle diameters were studied allowing to show the evolution of the resuspension with this parameter and to calculate dust resuspension rates and fractions during the air ingress