Researchers working on ExaSMR advance CFD–neutronics simulation tools

Scientists working on the Exascale Computing Project’s ExaSMR project have developed a comprehensive simulation framework targeting the entire small modular reactor (SMR) core, resolving foreseeable roadblocks to scaling up coupled simulations to the full core, such as the reduced order modeling of spacer grids and mixing vanes. Leveraging state-of-the-art computing resources has enabled the group to conduct the first-ever full-core pin resolved CFD simulation and generate high-fidelity fundamental insights for the first time into the nuclear reactor core—one of the most complex engineering systems. The newly developed model will significantly improve the accuracy of simulations of thermal-fluid behavior inside a SMR core without sacrificing computational efficiency. The group’s research was published in the July 2021 issue of Nuclear Engineering and Design.

Though experiments remain crucial to reactor design and safety analysis, given the extreme pressure/temperature and radioactive conditions inside the core, large-scale massively parallel simulations have become a vital complement to experiments, providing unique opportunities to advance our understanding of turbulent flows and thus better inform SMR designs. This work to develop tools applying exascale computing to couple computational fluid dynamics (CFD) and neutronics to solve the coupled multiphysics problem of SMRs at unprecedented fine resolution will play a critical role as we develop safer, more efficient nuclear reactors and help drive innovations in the growth of green, emission-free nuclear energy that contribute to US national security and economic prosperity.

The scientists are now working to develop full-core coupled multiphysics simulations integrating CFD with Monte Carlo particle transport and ensure they are ready to be ported to the upcoming exascale supercomputers. They are also developing a zonal hybrid modeling approach for the SMR full core, in which selected regions are modeled with explicitly detailed core structures and high-fidelity large eddy simulations and used to inform Reynolds-averaged Navier-Stokes modeling with momentum sources for the rest of the core.


Fang, Jun, Dillon R. Shaver, Ananias Tomboulides, Misun Min, Paul Fischer, Yu-Hsiang Lan, Ronald Rahaman, Paul Romano, Sofiane Benhamadouche, Yassin A. Hassan, Adam Kraus, and Elia Merzari. “Feasibility of Full-Core Pin Resolved CFD Simulations of Small Modular Reactor with Momentum Sources.” 2021. Nuclear Engineering and Design (July).

The cross-sectional view of the full core SMR model.