SECTION MENU    - The Repository Concept :: A design for safety :: Tunnel layout and design :: Natural features :: Engineered features   :: Selecting corrosion-     resistant materials   RELATED CONTENT :: Nuclear Waste Explained :: History of the Nuclear Waste Program :: Why Yucca Mountain? :: Project Oversight :: Public Involvement :: Site Recommendation and Approval

The repository design includes more than 50 horizontal tunnels for storing the waste (the tunnels are sometimes called "emplacement tunnels," "drifts," or "emplacement drifts"). These tunnels would be excavated in solid rock about 1,000 feet beneath the surface of the mountain and, on average, about 1,000 feet above the water table. The tunnels would be 16.5 feet in diameter and about 2000 feet long and would be reinforced with steel sets, rock bolts, and wire mesh to prevent rock from falling on the engineered features.

The underground location of the emplacement tunnels is based on several factors:

• the thickness of the overlying rock and soil
• the characteristics of the rock itself (such as porosity)
• the location of the fractures in the rock
• the distance from possible earthquake faults
• the depth to the water table
• stresses in the rock

Experts designed the underground layout of the emplacement tunnels to manage the heat that would be generated by the waste. This heat will influence moisture in the rock, humidity in the tunnels, and other conditions within the repository tunnels. In addition, the tunnels are designed so that any water that enters them will drain, by gravity, out of the tunnels downward and away from the repository.

• Fact Sheet: Nature and engineering working together for a safe repository