Comparison of Predicted Far-Field Temperatures for Discrete and Smeared Heat Sources

by Eric E. Ryder, Sandia Natl Lab, Albuquerque, United States,

Abstract: A fundamental concern in the design of the potential repository at Yucca Mountain, Nevada is the response of the host rock to the emplacement of heat-generating waste. The thermal perturbation of the rock mass has implications regarding the structural, hydrologic, and geochemical performance of the potential repository. The phenomenological coupling of many of these performance aspects makes repository thermal modeling a difficult task. For many of the more complex, coupled models, it is often necessary to reduce the geometry of the potential repository to a smeared heat-source approximation. Such simplifications have impacts on induced thermal profiles that in turn may influence other predicted responses through one- or two-way thermal couplings. The effect of waste emplacement layout on host-rock thermal response was chosen as the primary emphasis of this study. Using a consistent set of modeling and input assumptions, far-field thermal response predictions were made for discrete-source as well as plate source approximations of the repository geometry. Input values used in the simulations are consistent with a design-basis areal power density (APD) of 80 kW/acre as would be achieved assuming a 2010 emplacement start date, a levelized receipt schedule, and a limitation on available area as published in previous design studies. It was found that edge effects resulting from general repository layout have a significant influence on the shapes and extents of isothermal profiles, and should be accounted for in far-field modeling efforts.

Subject Headings: Waste management | Thermal analysis | Comparative studies | Temperature effects | Radioactive wastes | Computer models | Thermal properties | Coupling | Rocks | Rock masses | Nevada | North America | United States

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