Ling Zou

I. Molten salt reactors (MSRs) are a class of nuclear reactors in which molten salt serves as fuel and coolant, depending on the specific design. Benefiting from the unique properties of molten sal...

In recent years, there has been renewed interest in Molten Salt Reactors (MSRs) for their potential advantages compared to reactors that rely on solid fuel. In response to such interest, many methods and codes have been developed to capture the unique features of MSRs. Among them, the System Analysis Module (SAM) is a modern system analysis tool that provides fast-running, modest-fidelity, whole-plant transient analysis capabilities, essential for fast-turnaround design scoping and engineering analyses of advanced reactor concepts. For liquid-fuel MSRs, the complex physics and chemistry involved in MSR operation—such as reactor kinetics, fluid flow, heat transfer, and salt composition dynamics—pose significant challenges for system-level modeling. Specific modeling capabilities are needed for system-level transient simulation. This paper presents recent advancements in SAM capability enhancements for system-level modeling of MSRs, focusing on improved simulation fidelity, computational efficiency, and multi-physics integration. Key enhancements include the development of species transport, Delayed Neutron Precursor (DNP) drift, modified Point Kinetics Equations (PKE), decay heat modeling, key fission product behavior, salt corrosion, and thermal-hydraulic coupling, as well as code robustness and performance enhancements for MSR applications. The code enhancement allows for better predictive accuracy in safety analysis, transient behavior, and operational optimization, thus supporting the design and licensing of next-generation MSRs. Results from case studies are presented to demonstrate the benefits of these enhancements in accurately capturing key reactor transient behaviors.

Liquid metals such as lithium and lead–lithium eutectics are leading candidates for use as breeder and coolant materials in fusion blankets, where they enable both tritium breeding and efficient heat removal. In the presence of strong magnetic fields, magnetohydrodynamic (MHD) effects significantly influence flow distribution, pressure drop, and heat transfer, posing major challenges for blanket design and performance assessment. While high-fidelity computational fluid dynamics (CFD) tools exist for MHD analysis, there remains a lack of modern system-level analysis codes that integrate MHD effects with thermal–hydraulic and systems modeling.This paper presents recent developments at Argonne National Laboratory to address this gap through the implementation of MHD modeling capabilities in the System Analysis Module (SAM), a modern system analysis code built on the MOOSE framework. A reduced-order MHD modeling approach applicable to high Hartmann number and high interaction parameter flows is adopted, enabling efficient system-level simulations relevant to fusion liquid metal blankets. In parallel, MHD capabilities are being implemented in the high-performance CFD code NekRS to provide high-fidelity simulations for verification and model development.Analytical verification, code-to-code comparisons, and validation against historical experimental data from the Argonne Liquid Metal Experiment (ALEX) facility are presented for both square and round duct configurations under applied magnetic fields. The results demonstrate good agreement between SAM and NekRS predictions with analytical solutions in uniform magnetic fields; good agreement between SAM predictions with legacy MHD codes, and experimental measurements in varying magnetic fields. Ongoing and future work includes extension to insulating duct configurations, further NekRS development, and application to conceptual fusion blanket designs and ITER test blanket modules.