3-Way coupled thermohydraulic-discrete element-neutronic simulation of solid fuel, molten salt reactor

Abstract This study presents a three-way coupled numerical methodology between a fluid phase, a solid phase and neutronic heating within a buoyant pebble bed. Utilising coupled Computational Fluid Dynamics-Discrete Element Method-Neutronics (CFD-DEM-Neu.), the packing structure of the spherical solid phase and characteristic fluid flow structures are investigated. The geometry implemented is the pebble recirculation experiment (PREX) conducted at University of California, Berkeley (UCB), designed to simulate a pebble-bed, fluoride high temperature reactor’s (PB-FHR) core. Numerical coupling implemented accounts for pebble-pebble, pebble-wall, and pebble-fluid exchanges of momentum, while energy is applied to pebbles following a neutronic analysis and transferred between the present phases. Results show the methodology effectively describes the experimental pressure drop and expected packing structures of a randomly formed bed of mono-sized spheres. The temperature profiles of both fluid and solid phases are demonstrated for both uniform power and pebble-wise mapped power distributions.