Thermal-Hydraulic Results for the Aboveground Configuration of a Dry Cask Simulator

摘要

The purpose of the investigation described in this report was to produce data sets for the validation of assumptions associated with the thermal-hydraulic simulation of modern dry cask storage systems. Of particular interest were the steady-state cladding temperatures and the effect of elevated helium pressures in sealed canisters for aboveground designs. An existing electrically heated but otherwise prototypic BWR Incoloy-clad test assembly was deployed inside of a representative storage basket and cylindrical pressure vessel that represented the canister. The arrangement of a single assembly provided well-controlled boundary conditions and simplified interpretation of the results. An outer concentric duct was used to mimic conditions for an aboveground dry storage cask with canisters. Radial and axial temperature profiles were measured for a wide range of decay power and helium cask pressures. All steady state peak temperatures and induced flow rates increased with increasing assembly power. Peak cladding temperatures decreased with increasing internal helium pressure for a given assembly power, indicating increased internal convection. In addition, the location of the PCT moved from near the top of the assembly to ~1/3 the height of the assembly for the highest (8 bar absolute) to the lowest (0 bar absolute) pressure studied, respectively. This shift in PCT location is consistent with the varying contribution of convective heat transfer proportional with of internal helium pressure. The highest steady state PCT achieved was 715 K for 5.0 kW and 1 bar helium pressure. This temperature is in the range of the NRC limits for allowable PCT of 673 K for normal operation and 843 K for off-normal operation. On average, the CFD simulations are within 2 K and 12 slpm for PCT and air flow rate (Q), respectively. This is well within the maximum experimental uncertainties of 7 K and 35 slpm. The maximum difference across all tests was 8 K for PCT (4.5 bar He and 5 kW) and 43 slpm (1 bar and 5 kW). Based on this agreement, the modeling appears to have captured the underlying physics of the test apparatus.