Numerical Analysis of Heat Transfer Characteristic of Fast Reactor Spent Fuel Assembly Based on Porous Media and Effective Thermal Conductivity Models

During the shipping or transportation processes of the spent fuel assemblies, assemblies will be exposed to the gas region which has bad heat transfer characteristics, so the optimal properties should be focused on. In order to simulate the heat transfer characteristics of spent fuel assembly, the porous media model was used to simulate the flow resistance of spent fuel assembly, and the effective thermal conductivity model was used to simulate the heat transfer. The flow of fluid inside the spent fuel assembly was subjected to the laminar flow hypothesis under natural circulation conditions, so the impact of inertial force in the source of resistance was ignored. The effective thermal conductivity model was validated by comparing the simulation results with experiment data from SNL-LMFBR experiment. The calculation results show that under the horizontal placement condition, the temperature distribution curves of the spent fuel assembly are symmetrical. The asymmetrical distribution is presented under the vertical placement condition, and the high temperature region is shifted to the higher region of the spent fuel assembly.