Multiphysics Modeling Results for the High Flux Isotope Reactor to Support its LEU Conversion

Prashant K. Jain1, Marta Sitek2
1Oak Ridge National Laboratory
2Argonne National Laboratory
Published in 2023

Ongoing engineering design studies at Oak Ridge National Laboratory are exploring the feasibility of converting the High Flux Isotope Reactor (HFIR) from highly enriched uranium (HEU) to low-enriched uranium (LEU) fuel. HFIR is a pressurized light water-cooled and moderated research reactor with a core composed of involute-shaped HEU fuel plates and coolant channels. Advanced multiphysics computational fluid dynamics models have been developed in COMSOL Multiphysics® to simulate the steady-state operating conditions for both the current HEU fuel and the proposed LEU U3Si2-Al (uranium silicide dispersion) fuel designs. These models for HFIR's inner and outer fuel elements incorporate various essential physics, such as spatially dependent nuclear heat deposition, multilayer heat conduction, conjugate heat transfer, turbulent flows (using Reynolds Averaged Navier Stokes turbulence models), structural mechanics (thermal-structural interactions and fuel swelling), and oxide layer build-up. This poster presents the best-estimate nominal thermal hydraulics results for both the 85MW HEU core and the 95MW silicide LEU core. Furthermore, the thermomechanical verification and validation results are highlighted, showing a comparison against the legacy Cheverton-Kelley experimental data.