Experimental plan for investigating water movement through fractures: Yucca Mountain Project

The Yucca Mountain site in southern Nevada is being investigated by the Nevada Nuclear Waste Storage Investigations (NNWSI) project as a possible site for a nuclear waste repository. The manner in which the water flows downward from the repository through the unsaturated zone to the water table can affect the transport of radionuclides. The travel time of water across a rock unit is considerably shorter if the flow is predominantly through fractures than if it is predominantly through the rock matrix. Current data and postulated physical models indicate that there is little or no significant flow through fractures in the unsaturated zone at Yucca Mountain. Fracture data are required to increase confidence in this conclusion and would be used qualitatively to increase understanding and quantitatively in modeling. The evaluation of water flow in fractures is also necessary for abnormal scenarios where significant fracture flow may occur because of future climatic conditions. An experimental system is described for the purpose of investigating the movement of water through fractures. The system will be used to perform the tests described in this report. 14 refs., 11 figs., 3 tabs.