Comparison of CFD Calculations With Experimental Results for the YMP Scaled Natural Convection Tests

The Yucca Mountain Project (YMP) is currently designing a geologic repository for high level nuclear waste. The design encompasses two distinct phases, the pre-closure period where temperatures within the repository will be controlled by active ventilation, and the post-closure period where the repository will be sealed. A prerequisite for designing the repository is the ability to both understand and control the heat generated from the decay of the nuclear waste. This decay heat affects the performance of both the waste packages and the emplacement drift. The ability to accurately model the complex heat transfer within the repository is critical to the understanding of the repository performance. Currently, computational fluid dynamics codes are being used to model the post-closure performance of the repository. Prior to using the codes on the project they were required to be thoroughly validated. Eight pilot-scale tests were performed at the Department of Energy North Las Vegas Atlas Facility to evaluate the processes that govern thermal transport in an environment that scales to the proposed repository environment during the post closure period. The tests were conducted at two geometric scales (25 and 44% of full scale), with and without drip shields, and under both uniform and distributed heat loads. The tests provided YMP specific data for model validation. A separate CFD model was developed for each of the four test configurations. The models included the major components of the experiment, including the waste packages (heated steel canisters), invert floor, and emplacement drift (insulated concrete pipe). The calculated model temperatures of the surfaces and fluids, and velocities, are compared with experimental data.