Challenge Problem 4: Building a Flexible Multiscale Framework for Core Modeling

This conference paper discusses advances in reactor core thermal hydraulics, a crucial element of nuclear reactor safety. The complex interactions between thermal-hydraulics and fuel performance define the operating limits during normal and off-normal scenarios. The analysis of these phenomena poses challenges due to the vast array of temporal and spatial scales, making high-fidelity methods unfeasible for many large-scale domains and transients. The authors focus on the efforts within the NEAMS IRP project to improve the accuracy of traditional models, such as porous media models for pebble beds and subchannel analysis, through a multiscale core modeling approach. The paper presents and discusses high-fidelity Large Eddy Simulation results and novel experimental data used to benchmark these models. The authors stress that supercomputing simulations cannot significantly impact the design and safety analysis of advanced reactors without a suitable multiscale framework.