Researching a New Fuel for the HFIR: Advancements at ORNL Require Multiphysics Simulation to Support Safety and Reliability

F. Curtis, J.D. Freels
Oak Ridge National Lab, TN, USA

In response to the increasing awareness of the risks associated with the proliferation of nuclear materials, the Global Threat Reduction initiative has called for research reactors currently using highly enriched uranium (HEU) fuel to be converted to low-enriched uranium (LEU) fuel. The High Flux Isotope Reactor (HFIR), located at Oak Ridge National Laboratory (ORNL), is one such reactor that uses HEU fuel.

Using multiphysics simulation, ORNL engineers are conducting researching and working toward a new design for the HFIR that will preserve the reactor's performance, minimize negative effects on operation efficiency, and ensure reactor safety once the reactor’s fuel has been converted. This process requires that highly accurate multiphysics analyses be conducted into the fluid-structure interaction (FSI) of the reactor’s fuel plates and that an understanding of how the new density of the LEU fuel will impact reactor performance is achieved. ORNL researchers developed a model of the fuel plate deflections in COMSOL Multiphysics that they validated against representative tests using core configurations similar to the HFIR. The model will be used to test new design possibilities and eventually help facilitate the reactor's conversion to LEU fuel.

Simulation results showing the deflection in the leading edge of a HFIR fuel plate.