Numerical Study of Deposition Characteristic of Corrosion Product in Lead-bismuth Cooled Wire-wrapped Rod Bundle

Lead-based reactor using liquid lead-bismuth alloys as coolant has many advantages and is a promising type of fourth-generation reactors for a wide range of applications. However, the compatibility problem between liquid metal and structural materials exists in lead-based reactors. Corrosion products are generated from the core, precipitate as oxide particles at the cold end of the circuit, and undergo deposition in the steam generator, piping, and within the core as the coolant flows. During the flow process, lead-bismuth alloy will corrode the structural material and produce corrosion products, which will deteriorate the heat transfer and may cause safety hazards after deposition and aggregation on the surface of fuel rods. Therefore, a numerical study of particle deposition which takes a 19 wire-wrapped rod bundle fuel assemble as a reference object was carried out based on the discrete phase model (DPM) in ANSYS Fluent. Deposition characteristics of oxide particles in the rod bundle were obtained. Specifically, the axial and circumferential deposition distributions of corrosion product particulate oxide particles on the fuel rod cladding and hexagonal flow channel walls were investigated, respectively. Besides, effect of inlet flow velocity, fluid inlet temperature and particle diameter on the deposition characteristics were also analyzed. The results show that the main deposition location in the axial direction is the inlet of the rod bundle. In the circumferential direction, the main deposition position on the fuel rod is the gap between the windward side of the wire and the fuel rod surface, and the main deposition position on the hexagonal flow channel wall is near the prongs that correspond to the wrapped wire when it is in the angular sub-channel. The effect of the inlet boundary conditions on the particle deposition rate and deposition distribution is as follows. An increase in the inlet flow velocity enhances the deposition rate, but the lift effect decreases as the flow rate increases. An increase of the fluid inlet temperature enhances the deposition rate because the increase of inlet temperature reduces the density and viscosity of the fluid. As the particle diameter increases, the deposition rate increases because the increase in particle size of the particulate matter leads to an increase in the mass of a single particle, greater inertia, weaker flow field following, and easier deposition. The axial particle deposition distribution is insensitive to changes in fluid velocity, fluid temperature and particle size.