Multiphysics analysis of mechanical responses in micro-reactors under varied operating conditions

Abstract

Micro-reactors are a promising alternative for power production applications where traditional methods may not be feasible (e.g., space missions). Their design requires critical selection of materials, especially for moderator and fuel, to ensure long-term operation and optimal performance. This research focuses on developing computational analysis models for micro-reactors, aiming to explore their structural behavior under thermal and mechanical loadings. The micro-reactor model is based on the Zero Energy Breeder Reactor Assembly (Zebra) Kilowatt (kW) reactor design conceptualized at Los Alamos National Laboratory. This study investigates the thermal and mechanical responses of three distinct reactor models considering factors, such as boundary conditions, material properties, and thermal-mechanical loading. In this study, Beryllium Oxide (BeO), Beryllium (Be), Aluminum Oxide (Al2O3), and Magnesium Oxide (MgO) are chosen as materials for the reflector. Yttrium Hydride (YH) and Zirconium Hydride (ZH) are chosen as moderators. Uranium Nitride (UN) and Uranium Molybdenum (UMo) are chosen as reactor fuel materials. The thermal analysis predicts the deformation due to the thermal expansion within the reactor under steady operating conditions at 25 kWth, mimicking the maximum rated power of the Zebra kW design. The mechanical study simulates the system's response to forced vibration loads applied along the cooling channels, matching the natural frequency of the system. The results from both analyses show that Beryllium Oxide, Yttrium Hydride, and Uranium Nitride demonstrate the most optimal stress distribution in the system compared to other configurations investigated here. The results of this study can be developed into datasets to facilitate future machine learning studies, enabling the prediction of mechanical and thermal responses for micro-reactors.