Evaluation of the Use of Mercury Porosimetry in Calculating Hydrologic Properties of Tuffs from Yucca Mountain, Nevada

摘要

The geologic formations in the unsaturated zone at Yucca Mountain, on and adjacent to the Nevada Test Site (NTS), are currently being studied for consideration as the host rock for a radioactive-waste repository. Under the direction of the US Department of Energy, the Nevada Nuclear Waste Storage Investigations project is carrying out these studies. The formations are composed of tuffaceous materials, the hydrologic properties of which must be characterized to support analyses of the potential for water and radionuclide movement from the waste canisters to the accessible environment. Pore-size distributions have been determined for tuff samples by means of mercury porosimetry. These pore-size distributions are used in conjunction with capillary-bundle theory to calculate saturated hydraulic conductivities and water saturations as a function of pressure head for tuff matrix materials. The results are compared with those of more direct methods of measurement of these hydrologic properties to investigate the usefulness of employing pore-size distributions, as determined from mercury-intrusion testing, for estimating hydrologic properties of tuffs. The comparisons indicate that pore-size distributions can be useful in estimating saturated hydraulic conductivity values for tuffs from Yucca Mountain, but do not yield good comparisons with data on saturations as a function of pressure head obtained from more direct experimental measurements. (ERA citation 12:022311)