During 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 is 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 is devoted to the validation of the model implementation in ANSYS CFX. As one of the key parameters in the resuspension phenomenon is the friction velocity, CFD simulations are 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 are studied allowing to show the evolution of the resuspension with this parameter and to calculate dust resuspension rates and fractions during the air ingress.

 

References

 

\[1\]       M. W. Reeks and D. Hall, “Kinetic models for particle resuspension in turbulent flows: Theory and measurement”, *Journal of Aerosol Science*, vol. 32, pp. 1–31, 2001.

\[2\]       S. Peillon, A. Roynette, C. Grisolia and F. Gensdarmes, "Resuspension of carbon dust collected in Tore Supra and exposed to turbulent airflow: Controlled experiments and comparison with model", *Fusion Engineering & Design,* vol. 89, pp. 2789-2796, 2014.

\[3\]       T. Gélain, A. Rondeau, S. Peillon, J.-C. Sabroux, and F. Gensdarmes, “CFD modelling of the wall friction velocity field in the ITER tokamak resulting from airflow during a loss of vacuum accident—Consequences for particle resuspension, ”*Fusion Engineering & Design.*, vol. 100, pp. 87–99, 2015.

\[4\]    Nerisson, P., Simonin, O., Ricciardi, L., Douce, A., Fazileabasse, J. (2011). Improved CFD transport and boundary conditions models for low-inertia particles. Computers & Fluids 40 (1), 79-91.


Implementation of a Particle Resuspension Model in a CFD Code: Application to an Air Ingress Scenario in a Vacuum Toroidal Vessel

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