Impact of Coupled DEM and Hyper-Fidelity Depletion on Pebble Bed Burnup

Pebble Bed Reactors (PBRs), with their unique operational dynamics and fuel design, present significant simulation challenges.Pushing the boundaries and leveraging current advances in computational resources and methods, the Hyper-Fidelity Depletion (HxF) approach, capable of tracking each pebble's history individually, was developed.This study explores the impact of motion and geometry in PBRs using the HxF approach, focusing on the generic Fluoride-salt-cooled High-Temperature Reactor (gFHR) model.It compares the outcomes of discrete motion and the Discrete Element Method (DEM) motion, with and without a defueling chute, to assess their effects on reactor simulation.Results show that the choice of motion approach significantly influences simulation results (pebble trajectory, residence time, and equilibrium state).Despite its higher computational demands, the DEM approach provides a more accurate representation of pebble motion within PBRs compared to the discrete motion method, resulting in different operational parameters such as pebble packing, flux distributions, and cumulative parameter profiles.The study also shows the effects of introducing realistic geometry components, which cause changes in operating conditions, emphasizing the importance of the modeled geometry and motion techniques for high-fidelity calculations.The research presented in this paper highlights the use and efficiency of the HxF tool in simulating full-scale PBR operations and determining their equilibrium states.