As a result of the end of the cold war, at least 11,000, and possibly up to 20,000, plutonium pits are projected to be stored in temporary storage facilities in the United States for up to 50 years. The storage container, the ALR8(SI), must be investigated for quality and longevity requirements. As a part of validating the U.S. Department of Energy's quality requirements, a computer model was developed and validated to predict the temperature distribution within both the stored components and the internal structure of the ALR8(SI) container to analyze the thermal performance of the container. Experimental data were obtained and served as a comparison for examining the validity of the numerical model. The thermal response of the ALR8(SI) under normal storage conditions was investigated experimentally. Results were obtained for different values of heat generation rate (15, 20, 25, and 30 W), outside container temperature (20, 25, and 30°C), and different backfill gases (air, argon, and helium). A finite element model consisting of a thermal and a flow domain was created and solved simultaneously using SDRC I-DEAS Master Series 6. Solutions were obtained for most of the experiments performed. The predicted temperature distribution matched quite well in magnitude with the experimental data. For most locations, predicted temperatures deviated less than 2°C from the experimental temperatures, whereas the maximum deviation was around 4°C. In most cases, the maximum-recorded temperature exceeded the quality limit of 60°C. A theoretical study of the heat transfer mechanisms showed either conduction through the backfill gas or natural convection as the primary mode of heat transfer, depending on the backfill gas. In an attempt to reduce the interior temperatures of the ALR8(SI), a modification to one of the ALR8(SI) components was made in the numerical model to enhance heat transfer. Solutions of this modified container predicted significantly lower temperatures of the interior.