Neutronic and Thermal-Hydraulics Coupling Analyses on Prismatic Triso-Fueled Gas-Cooled Reactors Using Monte Carlo and Computational Fluid Dynamics Method

Abstract

This paper presented a high-resolution neutronic/thermal-hydraulics coupling approach using Monte Carlo (MC) code RMC and Computational Fluid Dynamics (CFD) code ANSYS Fluent, and applied the coupling calculation on a micro modular prismatic high temperature gas-cooled reactor (HTGR). The multiscale treatments for the TRISO particles were considered including the property homogenization and the local heat conduction. The coupling scheme based on Picard iteration realized efficient text-free data transfer through hierarchical data format (hdf), and introduced a geometry-independent mapping strategy by separating the power and thermal data tallying meshes from the computing meshes to achieve versatility. Verification results showed great agreements to the previous study.Simulations and analyses were performed on a 1/12 micro HTGR core model with simplifications. Maximum fuel temperature rise of ~30 K and axial temperature fluctuation of ~10 K were observed when the power profile was radially tallied on the sub-pin level and axially tallied on the sub-fuel element level, showing that the high-resolution coupling can capture detailed features and provide conservative results. The coupling provided negative reactivity feedback (-1107 pcm) mainly due to the fuel temperature Doppler effect. The maximum fuel temperature obtained from the coupling calculation was 77 K higher than that of the decoupled case, further showing the conservative nature of the neutronic/thermal-hydraulics coupling. The results also exposed the azimuthal fuel temperature nonuniformity. The high-resolution coupling calculation realized in this study reveals refined neutronic and thermal-hydraulics parameters for the micro HTGR, thus providing reliable references for both the core design and coupling using lower-resolution methods.

Keywords: Neutronic and thermal coupling, High-resolution, High temperature gas-cooled reactors, Monte Carlo, Computational Fluid Dynamics, TRISO