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Model Predictive Control of a Small Modular Reactor with Partial Steam Diversion to Thermal Energy Storage with RELAP5-3D

Jackson Ivory, Jaron Wallace, Matthew Memmott

Nuclear Science and Engineering / Volume 200 / Number 7 / July 2026 / Pages 1606-1626

Research Article / dx.doi.org/10.1080/00295639.2025.2537501

Received:March 20, 2025
Accepted:July 12, 2025
Published:May 28, 2026

As energy demand grows, nuclear power has gained attention. Small modular reactors (SMRs) show significant potential, but as a baseload power, nuclear reactors must adapt to dynamic shifts in demand. Thermal energy storage systems offer a solution, with control being essential. This study uses a model predictive controller to match the load of the system with the demand of the power grid over 24 hours. RELAP5-3D control variables were created and controlled using Python GEKKO to simulate load-following. Several transient scenarios were analyzed with this combined system to analyze safety. This study found that load and demand can be matched better when steam is diverted partially between the TES and regular turbine rather than completely to one or the other. A 66% supply-demand mismatch decrease was found compared to baseload in this work, and a 52% decrease was found when compared to prior work using full steam diversion. Partial steam diversion offers a more robust solution for demand mismatch.