COMPUTATIONAL FLUID DYNAMICS MODELING APPROACH TO EVALUATE VSC – 17 DRY STORAGE CASK THERMAL
A numerical simulation of flow and heat transfer in a ventilated concrete dry storage cask system–17 (VSC–17) is performed and results compared with experimental data to assess the validity of the computational approach. The measurements of steady state temperature distributions on the cask surface, concrete surface, air flow channels, and fuel canister guide are available. Numerical simulations were carried out for normal operating conditions, where both the inlet and outlet vents are open, and for off-normal condition when normal air circulation is interrupted because of blocked vents. Results include the flow and temperature pattern in the ventilated storage system. Computed results were compared with experimental data for axial temperature distribution along the fuel assembly and radial temperature distribution along the storage assembly system. The effect of the turbulence model on temperature distribution pattern was also studied. For all the simulated cases, the computed results showed a trend similar to the experimental observation but did not model exactly. Computed peak cladding temperature in all the simulation cases was slightly higher than the experimental data. Heat transfer results showed some variation due to difference in backfill gas. A study of different k-ε and k-ω turbulence models showed very little effect on temperature distribution.
Use of Fuel Assembly/Backfill Gas Effective Thermal Conductivities to Predict Basket and Fuel Cladding Temperatures Within a Rail Package during Normal Transport
Two-dimensional finite element thermal simulations of large rail casks designed to transport spent nuclear fuel assemblies were performed for normal conditions. Two different effective thermal conductivity models, developed by other investigators, were implemented within the basket openings that support the fuel assemblies. The effective thermal conductivity models affect the peak cladding temperature directly by influencing the temperature difference between the hottest cladding at the cask center and the walls that surround it. It also affects it indirectly by influencing the center basket wall temperature. The fuel assembly heat generation rates that cause the peak cladding temperature to reach the allowed limit were determined for both effective thermal conductivity models. At those generation rates the basket wall temperatures in the periphery of the package were highly nonuniform. The basket wall temperatures determined in this work will be used in future studies to develop improved thermal models of fuel assemblies.
Numerical Simulation of Thermal Sensitivity for Explosives
In order to compare the thermal sensitivity of several typical explosives, this article solved numerically one-dimensional transient heat conduction equation including thermal decomposition for explosives with finite difference method. The explicit difference equations under different boundary conditions were established, and the corresponding stability criterion was derived. The ignition times for typical explosives were calculated, which was used to evaluate thermal sensitivity of explosives.