A fem study on the particle-wall impaction of graphite dusts in high temperature gas-cooled reactors (HTGR)

The graphite dust, produced by friction of fuel pebbles, is a significant concern in potential accidents of HTGR because the graphite dust is closely coupled with radioactive fission product. The study of graphite particle-wall impaction is important to accurately estimate deposition rate of graphite dust. In this paper, both the spherical and non-spherical particle-wall impaction process are discussed based on FEM. By combining derived adhesion force with FEM, the results agree well with JKR model. The damping dissipation is employed to describe the energy loss, corresponding dimensionless damping coefficient is defined to establish the relation between damping coefficient and material properties. Meanwhile, the results of non-spherical particle impaction are also well predicted by dimensionless damping coefficient. It is also shown both adhesion force and damping dissipation are important at low incident velocity, while the effect of adhesion force is negligible and the dissipation is the dominant mechanism at high incident velocity. Besides, the contact area remains perfectly elastic deformation and never gets into failure when the incident velocity is lower than 20 m/s due to size effect. The results provide a possible approach for non-spherical particle-wall impaction, which can be combined with computational fluid dynamics (CFD) to estimate the deposition rate of graphite dust in HTGR.