Abstract

The deployment of molten salt reactors (MSRs) as next-generation nuclear technology requires accurate thermophysical property data, validated system models, and advanced control strategies to ensure safe and economically competitive operation. This dissertation, Enhancing Fuel Performance of Molten Salt Reactors Through Improved Thermophysical Property Data, High-Fidelity Simulation, and Advanced Control Strategies, integrates experimental measurements, thermal hydraulic simulation, and model predictive control (MPC) to enhance understanding of MSR fuel behavior under steady state and transient conditions. New density and heat capacity measurements of UF4-FLiNaK molten salts were obtained using Archimedean and differential scanning calorimetry methods, respectively, to address critical gaps for fueled salts. These measurements revealed undocumented thermodynamic transitions with implications for heat transfer modeling and safety analysis. A full-system RELAP5-3D model of the BYU Molten Salt Microreactor, coupled with a sodium cooling loop and supercritical CO2, was developed to simulate fuel performance and safety margins. A loss of flow accident is analyzed throughout this work. Experimental data were used to develop custom fluid property tables, which were incorporated into RELAP5-3D. Comparisons between standard and custom fluid file usage are analyzed. Advanced control strategies were developed to examine the reactivity control aspects of the RELAP5-3D reactor. Python GEKKO was used to create an MPC to adjust the reactivity of the reactor based on temperature setpoints during steady state and transient operation. Effective reactivity optimization was accomplished. Additionally, an MPC controller was developed for a small modular reactor (SMR) to examine the load-following ability of nuclear power plants. The controller effectively matched electricity supply and demand and reduced mismatch by 300 MW when compared to previous work. This dissertation provides validated thermophysical property data, improves predictive modeling of fuel performance, and demonstrates advanced control strategies for nuclear power plants. These contributions directly support reactor licensing efforts, enhance transient predictability, and strengthen the case for the commercial deployment of molten salt reactor technology.

Degree

PhD

College and Department

Ira A. Fulton College of Engineering; Chemical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-12-16

Document Type

Dissertation

Keywords

molten salt, thermal hydraulics, thermophysical properties, fuel salt, thermodynamic salt transition, RELAP5-3D, model predictive control, small modular reactor, thermal energy storage, load following

Language

english

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