CFD analysis of spent fuel dry cask storage system for High burnup nuclear fuel

Storage of nuclear spent fuel and cooling of the fuel assembly is one of the vital requirements for nuclear safety. This engineering technology involves a dynamic thermo-fluid phenomenon in the dry storage casks. Therefore, this study investigated HI-STORM 100 dry cask storage container for thermal-fluid with sensitivity analysis using 3D Computational Fluid Dynamics (CFD) simulations. It is a vertical concrete cylindrical structure (6.09 m height and 3.36 m diameter) containing a welded stainless-steel sealed barrel multi-purpose canister (MPC) for storing the fuel components replaced by the reactor. MPC-32 storage barrel (4.85 m height, 1.78 m outer diameter) and Westinghouse 17 × 17 high burnup (45GWd/MTU) Pressurized Water Reactor (PWR) fuel assembly is selected in this research. 2D and 3D models of this assembly were simulated using CFD with porous media assumption. Further, Boussinesq approximation and incompressible ideal gas models are adopted in simulation; and standard k-ε and k-ω Shear Stress Transport (SST) turbulence models were also compared under natural convection. The internal flow and temperature of the MPC by the incompressible ideal gas model were found to be in line with the actual situation. The standard k-ε model can cause abnormal results at the high-temperature position. The sensitive factors are analyzed to predict the temperature distribution and flow field characteristics of the system during 10–55 cooling years. During this period, the decay thermal power of nuclear waste, the maximum temperature of the system and shell; the air outlet temperature and the volumetric flowrate decreased. Under non-uniform thermal conditions, the heat dissipation performance was studied defining the decay heat ratio (X). The heat dissipation performance of the system was found better when X ≥ 1, and the maximum temperature of the fuel assembly rise when X < 1.