Abstract
Three-dimensional calculations that explicitly represent a realistic mixture of waste packages (WPs) are used to analyze decay-heat-driven thermal-hydrological behavior around emplacement drifts in a potential high-level waste facility at Yucca Mountain. Calculations, using the NUFT code, compare two fundamentally different ways that WPs can be arranged in the repository, with a focus on temperature, relative humidity, and liquid-phase flux on WPs. These quantities strongly affect WP integrity and the mobilization and release of radionuclides from WPs. Point-load spacing, which places the WPs roughly equidistant from each other, thermally isolates WPs from each other, causing large variability in temperature, relative humidity, and liquid-phase flux along the drifts. Line-load spacing, which places WPs nearly end to end in widely spaced drifts, results in more locally intensive and uniform heating along the drifts, causing hotter, drier, and more uniform conditions. A larger and more persistent reduction in relative humidity on WPs occurs if the drifts are backfilled with a low-thermal-conductivity granular material with hydrologie properties that minimize moisture wicking.
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Acknowledgement
We acknowledge the review of Jim Blink, the editorial assistance of Robert Kirvel, and the graphical support of Rick Wooten and Dan Fletcher. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract W-7405-ENG-48 and was supported specifically by the Yucca Mountain Site Characterization Project at LLNL.
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Buscheck, T.A., Nitao, J.J. & Ramspott, L.D. Near-Field Thermal-Hydrological Behavior for Alternative Repository Designs at Yucca Mountain. MRS Online Proceedings Library 465, 1029–1036 (1996). https://doi.org/10.1557/PROC-465-1029
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DOI: https://doi.org/10.1557/PROC-465-1029