Microreactor Automated Control System Test Bed Digital Architecture for Real-Time, Hardware-in-the-Loop Simulation

This work describes progress made toward the development of a real-time, hardware-in-the-loop test bed for nonnuclear testing of microreactor control schemes and failure modes. Nonnuclear testing is a crucial step in developing robust control algorithms for managing microreactor dynamics. Creating a hardware-in-the-loop simulation harnesses the realistic dynamics of physical analogue systems while considering the challenges of variable communication delay. This collaborative effort between Oak Ridge National Laboratory and Idaho National Laboratory resulted in a LabVIEW-based gRPC communication protocol. The protocol couples a TRANSFORM (Transient Simulation Framework of Reconfigurable Modules) Modelica simulation of nuclear components with the ViBRANT physical hardware for realistic feedback and visual representation of control action in real time. A modular Python client structure was developed to manage functional mock-up unit-based Modelica and real-time gRPC communication. Hardware-in-the-loop testing indicated that the modeled reactor simulation with a natural-convection, molten-salt coolant loop configuration responds well to proportional-integral-derivative control of drum positioning for modulation of reactor core power. However, future efforts will be made to explore the added thermal inertial delay of system-level control and downstream demand changes. Development of this platform with a generalized methodology provides a foundation for exploring a variety of reactor configurations and failure modes in rapid order to provide insight into the most effective avenues of study for further research and development.