Development of a MOC-based multiphysics coupling method for analysis of FCM-fueled micro gas-cooled reactor

At present, Fully Ceramic Microencapsulated (FCM) fuel with randomly dispersed tri-structural isotropic (TRISO) particles is widely used in gas-cooled microreactors. Gas-cooled microreactors usually exhibit limited volume and complex structure, with tightly coupled multi-physical fields inside the core, presenting challenges for multiphysics analysis. In this work, a MOC-based multiphysics coupling method for analysis of FCM-fueled micro gas-cooled reactor within the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework is developed and verified. The fuel assembly calculation results show that the generated multi-group cross-section (MGXS) at different temperature points exhibits high computational accuracy. The MOC-MOOSE results exhibit a high computational accuracy in k_eff, power distribution, and temperature field. Meanwhile, the calculation cost for the MOC-MOOSE method is only 10 % of that required by the benchmark solver, demonstrating high computational efficiency. At last, the full-core multiphysics coupling was conducted. The three-dimensional pin-by-pin fuel power distribution was obtained, with the highest power occurring in the outermost fuel rods of the peripheral fuel assemblies at the middle plane of the axial active region. The maximum fuel, matrix, and coolant temperatures are 1698 K, 1206 K, and 1002 K, separately.