Parametric Thermal Analysis for Codisposal Waste Package Canister

The engineering viability of disposal of aluminum-clad, aluminum-based spent nuclear fuel (Al-SNF) in a geologic repository requires a thermal analysis to provide the temperature history of the waste form. Calculated temperatures are used to demonstrate compliance with criteria for waste acceptance into the Mined Geologic Disposal System and as input to assess the chemical and physical behavior of the waste form within the waste package (WP).A thermal analysis methodology was developed to calculate peak temperatures and temperature profiles of Al-SNF in the DOE spent nuclear fuel canister within a codisposal WP. A two-dimensional baseline model with conduction and radiation coupled heat transport was developed to evaluate the thermal performance of Al-SNF directly stored in a canister in a codisposal WP over the range of possible heat loads and boundary conditions. In addition, a conduction model and a detailed model which includes convection were developed to identify the dominant cooling mechanism under the present WP configuration, to investigate physical cooling mechanism in detail, and to estimate the conservatism imbedded in the baseline model.The results of the baseline model showed that the direct disposal configuration with a helium-filled WP satisfied the present waste acceptance criteria (WAC) for the WP design in terms of the peak temperature criterion, Tmax < 350 degrees C, under the reference boundary conditions. A period of 10 years' cooling time for the decay heat loads of the SNF and the High-level Waste Glass Log (HWGL) regions was used as one of the reference design conditions