Framatome’s unified single-phase CFD methodology for fuel design and analysis

Computational Fluid Dynamics (CFD) has become an invaluable tool for design and analysis of PWR and BWR nuclear fuel. In the last decade, Framatome developed CFD methodologies tailored to address specific problems from fuel thermal performance [1], [2], Crud-Induced Power Shift and Crud-Induced Localized Corrosion (CIPS/CILC) [3] or grid-to-rod fretting (GTRF), to large-scale problems such as fuel assembly bow [13], [14] reactor core thermal-hydraulic characterization [4], or mixing in the lower and upper plena. The stand-alone methodologies evolved over the years to reflect improvements in STAR-CCM+® code physics modeling and meshing capabilities [5], [6], availability of new experimental data for validation, and augmented computing power. Recently, a unified multi-purpose methodology that relies on robust CAD (Computer Aided Design), advanced meshing strategies, sound turbulence modeling, and standard wall functions was established. The shared framework ensures a high degree of commonality between pressure loss, flow field, and thermal calculations, which improves consistency and modeling efficiency. The setup has been optimized and rigorously validated against experimental data from test facilities such as Framatome’s Le Creusot and Erlangen Technical Centers, or Richland PHTF, the CEA’s HERMES and OMEGA lops, or EDF’s MANIVEL loop. The legacy single-phase methodologies already ensured predictions were within +/-5% of measurements; with the unified setup, the predictions are further improved, the validation error being consistently reduced for all applications. Also, an automated process has been developed for the implementation of the new methodology; it relies on consistent CAD treatment, mesh generation, and model setup, which ensures modeling efficiency and user-independence. The new generation modeling package provides a reliable tool for analysis and virtual testing, critical to the improvement of current fuel products (ATRIUM 11, AFA 3G, GAIA, HTP) and to the development of advanced ATF (Accident Tolerant Fuel) and metallic fuel designs.