Numerical investigation of particle behavior and cladding oxidation in a PWR fuel bundle by CFD methodology

Abstract

The knowledge of local conditions in a PWR reactor core at high temperature and pressure are important for the optimization of the fuel assembly reliability. In particular it is of interest to distinguish between the effects of the local temperature distribution, the effects of the local concentration of the moderator’s chemical or structural components and the effects of the cladding material property variations to better interpret inspection results of fuel assemblies and to improve conclusions for design optimization.Since local parameters cannot be measured during operation, Computational Fluid Dynamics (CFD) is the method of choice to calculate the local fuel rod conditions. For example, the movement of discrete, virtual particles in the moderator can today already be simulated by a Lagrangian model with the particle tracking approach for CRUD deposition simulation. The development of a reference 3D PWR corrosion and CRUD deposition model was started which can calculate local parameters on a fuel rod surface to predict oxide thickness and component deposition taking into account the mixing effects during the moderator transport. The calculated 2D surface coolant temperatures were coupled to a dedicated fuel rod corrosion model, covering the full fuel rod in azimuthal and axial direction.