A Whole-Core Multiphysics Microreactor Simulator

Microreactors represent a transformative advancement in nuclear energy, offering compact, flexible, and transportable power generation for remote locations, industrial applications, and national security needs. Their unique configurations, including Tristructural Isotropic (TRISO) fuel, alternative cooling methods such as heat pipes, and innovative control mechanisms, require specialized simulation tools that extend beyond traditional reactor analysis frameworks. This work presents a novel multiphysics modeling approach integrating Monte Carlo neutron transport with detailed thermal solvers to enhance predictive capabilities for microreactor design and safety assessment. The developed simulation framework couples the Shift Monte Carlo neutron transport code with the pyMP platform, enabling the accurate representation of steady-state and transient reactor behavior. pyMP incorporates a flexible shift driver package for interfacing with Shift, a thermal package containing conduction and convective cooling solvers, and a multiphysics package responsible for integrating all physics domains. Two representative microreactor models were analyzed: a gas-cooled TRISO-fueled design with control rods (Core A) and a heat pipe-cooled design with rotating control drums (Core B). Results from power ramp and control drum search studies demonstrate the framework’s capability to model reactivity feedback, heat transfer, and control mechanisms with high fidelity. These developments mark a significant step toward comprehensive, high-accuracy microreactor simulation, supporting design optimization and regulatory assessment.