Study of thermal hydraulic characteristics of a pebble bed reactor using computational fluid dynamics

This research investigates the thermal hydraulic characteristics of a Pebble Bed Reactor (PBR) core with different pebble diameters using commercial software CFX. The coolant is water. A 'Bridge' model is employed to simplify the contact points; the standard k-ε model is adopted to simulate flow turbulence. Velocity and temperature fields as well as Nusselt number are obtained and analyzed under different pebble sizes; the influence of pebble size on flow and heat transfer is also discussed. Then, the well-known KTA correlation is adopted to validate the simulation results. The results show that different pebble diameters do not change the flow distribution significantly. Four areas with low temperature appear at the four pore regions and four pairs of eddies at the intervals of the upper and lower bridges both impact the thermal hydraulic characteristics distribution. In addition, the maximum temperature increases and pressure drop decreases with the enlarging of pebble diameters. The study could provide the basis for further experimental research and design improvement of fuel spheres in PBR. (author)