Thermophoretic Particle Deposition: A Computational Fluid Dynamics Approach for Estimating Hotspots

In the event of a catastrophic nuclear accident, fission products are released from the fuel and scattered into the primary circuit as fumes, vapors, or minute particles (aerosols). Physical processes, such as gravitational impaction, turbulent dispersion, and thermophoresis can cause particles to accumulate in the primary circuit and deposit on the structure and equipment walls. Different studies [1,2] have underlined the role of thermophoresis as a significant mechanism for particle deposition. Using the concept of thermophoresis, the current study aims to investigate particle deposition in this context. The effect of thermophoresis on particle impaction is modeled using the commercial CFD code STAR-CCM+ and the applied model is validated against the available data from the STORM experiments within the scope of the International Standard Problem-40 [3] which is concerned with deposition and resuspension of particles in pipes under the effect of thermal forces. Also, estimated deposition velocity and relaxation time of particles were compared with Liu&Agarwal's experiments for isothermal condition. In this study, we focused on particle transport rather than the detailed process of deposition on the surface which is represented by adhesion probability and the particle rebound probability from the surface. The suggested CFD model is also suitable for analyzing large geometries like nuclear power plant containment. Therefore, it may also be utilized to enhance understanding of radionuclide dispersion after a severe accident and the identification of radioactive hotspots inside containment vessel during decommissioning operations.