Numerical Simulation on 3D Flow in the Fuel Transfer Canal and Local Flow Field Analysis

By application of CFD codes, 3D complex flow field and temperature field in the transfer canal are simulated. It indicates that there is obvious cross-flow in the complex flow path of spent fuel container, and the natural circulation flow brings an inhomogeneous heat-transfer condition to the spent fuel assembly. A model of typical unit of canal is built, and local flow field and temperature field are analyzed with CFD code. The results of thermal hydraulics analysis could be a good reference for nuclear safety research on spent fuel assembly. Considering a conservative operating condition, a case with conservative boundary conditions is investigated by CFD code with 3D model. The result shows that fuel rods in the local region, which are in the container upside and far from holes of wall and roof, get the worst cooling effect, and even maybe boiling occurs in clad surface. Based on the thermal-hydraulics analysis, optimized mechanical designs of container are suggested, the new design would optimize the local flow field, and increase the flow velocity of water, to construct more unhindered convection there, as a result, make spent fuel rods in the bad cooling region get better cooling.