CFD MODELING AND EXPERIMENTAL VALIDATION OF FLOW CHARACTERISTIC IN A STRUCTURED PEBBLE BED

Spherical fuel assembly with light water reactor technology has prominent advantages on safety and fuel cycle, for its large specific surface. However, larger specific surface brings larger pressure drop over the core comparing with traditional rod fuel assembly. A test facility was built to investigate the flow characteristics on a mono-size sphere packed bed with a diameter of 3mm The Reynolds number varies from 52 to 665, and the flow pattern ranges from Darcy flow to turbulent flow. Pressure drop of the whole test part was measured with relevant components to ensure the expected inlet conditions. Results of tests with different inlet flow rates and temperatures were obtained. Numerical simulations were taken on the same packed structure and defined problem using CFD method. Quite good agreement was reached on pressure drop over the test part, and detailed flow information was also obtained. Furthermore, the scaling effects, including longitude pressure drop, cross section pebble bed size, and sphere diameter were analyzed using CFD method.