Simulating the Dynamics of Spouted-Bed Nuclear Fuel Coaters

• Published in: Chemical vapor deposition Vol. 13; no. 9; pp. 481 - 490
• Main Authors: Pannala, S., Daw, C. S., Finney, C. E. A., Boyalakuntla, D., Syamlal, M., O'Brien, T. J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.09.2007; WILEY‐VCH Verlag
• Subjects: Coatings; Fluid dynamics; Nuclear fuels; Spouted-bed coating
• ISSN: 0948-1907; 1521-3862
• DOI: 10.1002/cvde.200606562

We describe simulation studies of the dynamics of spouted beds used for CVD coating of nuclear fuel particles. Our principal modeling tool is the Multiphase Flow with Interphase eXchanges (MFIX) code that was originally developed by the National Energy Technology Laboratory (NETL) for fossil energy process applications. In addition to standard MFIX features that allow coupling of transient hydrodynamics, heat and mass transfer, and chemical kinetics, we employ special post‐processing tools to track particle mixing and circulation as functions of operating conditions and bed design. We describe in detail one major feature of the dynamics, which is the occurrence of very regular spontaneous pulsations of gas and particle flow in the spout. These pulsations appear to be critically linked to the entrainment and circulation of solids, and they produce readily accessible dynamic pressure variations that can be used for direct comparisons of model predictions with experiments. Spouted‐bed dynamics are important from a CVD perspective because they directly determine the magnitude and variability of the concentration and species gradients in the zone where reactant gases first come into contact with hot particles. As this unsteady spouted‐bed environment differs from other types of CVD reactors, the design and scale‐up of such reactors is likely to involve unique modeling issues. Our primary goal here is to lay the groundwork for how computational simulation can be used to address these modeling issues in the specific context of nuclear fuel particle coating. This paper reports simulations of the spouted beds used for CVD coating of nuclear fuel particles. A continuum computational fluid dynamics (CFD) tool has been used to study the dynamics of the spouted beds and in particular the regular spontaneous pulsations of gas and particle flow in the spout. These pulsations are important for the CVD process as they appear to be critically linked to solids entrainment and circulation.