Case Study: Oak Ridge National Laboratory achieves validated multiphysics simulation for safe, reliable HFIR LEU fuel conversion with COMSOL Multiphysics

Nuclear-Safety-Related SQA Procedure Automation with Custom Applications

Oak Ridge National Laboratory needed to evaluate and redesign the High Flux Isotope Reactor (HFIR) to convert from highly enriched uranium (HEU) to low‑enriched uranium (LEU) while preserving neutron flux, safety, and operational performance. To analyze the coupled thermal, fluid, and structural effects on the reactor’s unique involute fuel plates, ORNL researchers turned to Comsol, using Comsol Multiphysics for multiphysics fluid‑structure interaction (FSI) simulation.

Using Comsol, ORNL built fully coupled FSI models incorporating turbulent CFD and structural deformation, validated against experimental data from the Advanced Neutron Source. The Comsol simulations produced excellent agreement with measured fuel‑plate deflections across multiple flow rates, improved stability and accuracy over weakly coupled methods, and helped refine LEU fuel‑meat and core designs—providing quantified, validated results to support regulator review and the safety basis for conversion planning.

Oak Ridge National Laboratory

Jim Freels

Senior Research Staff Member