Year
2005
Abstract
Rejection of heat from spent fuel is required to employ passive means and numerical methods are available to perform these evaluations. The target design employs natural convection internal and external to a canister containing the spent fuel. The canister is placed inside a vertical concrete cask. Airflow up the annulus between the canister and the concrete cask efficiently rejects the spent fuel heat. Certain simplifications are used in this evaluation internal to the canister since modeling of individual fuel rods and assembly grids is not practical. While a porous media model can represent the canister internals, there are different modeling options to incorporate the effect of the grids and the fuel rod array. Another area of modeling which can affect the maximum fuel clad temperatures is the fluid modeling in the annular region on the outer surface of the canister. Depending on the assignment of the characteristic length, the flow could be considered to be laminar, transitional or turbulent. Using the thermal test data of a vertical concrete cask, the associated thermal analyses are performed to evaluate the acceptability of turbulence modeling in the air annulus near the canister wall.