Earth Sciences Division (ESD) Department of Energy (DOE) Lawrence Berkeley National Laboratory (LBNL)

The Yucca Mountain Project: Ambient Testing: Micro-climate dynamics in the near-drift environment at Yucca Mountain

A key issue regarding the performance of the potential high-level radioactive waste repository at Yucca Mountain, Nevada, is the likelihoodof precipitation percolating a vertical distance of ~300 m through fractured unsaturated rock into drifts containing waste packages. Water enhances waste package corrosion and is required for transport of released radionuclides.  To evaluate the propensity for seepage into tunnels at Yucca Mountain, a 5 m diameter, 2.7 km long tunnel, commonly referred to as the Cross Drift (CD), was excavated in 1998, branching off from the main Exploratory Studies Facility tunnel. Sections of this tunnel have been isolated from ventilation for extended periods over the last four years. We have measured relative humidity and temperature, and made periodic observations of liquid water in the CD. During this observation period, the terminal section of the drift was partitioned into four sections by bulkheads, and ventilation to these sections was minimized to a few days.  We compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation. Observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts.  Observations, measurements, and analysis indicate the need for a model that includes fracture-dominated vapor transport as a significant contributor to total water flow into the drifts.

Figure 1.(A) Cross-sectional view of the Cross Drift, showing location of various in-drift features; (B) Location of bulkhead doors along the terminal section of the Cross Drift.

Figure 2. Location of monitoring borehole below the excavation path of the tunnel boring machine. Sensors located within this borehole monitored changes in moisture content resulting from construction-related activiities.

Figure 3. Conceptual models: (A) mixed tank model; (B) diffusion model; and (C) diffusion through an inert ring model

Related Publications

  • Salve, R., and T. Kneafsey, 2005. Vapor-phase transport in the near-drift environment at Yucca Mountain Water Resources Research 41: doi:10.1029/2004WR003373.

For more information, please contact:

Rohit Salve
Earth Sciences Division
Phone: 510-486-6416
Email: r_salve@lbl.gov