Facts and figures of the Yucca Mountain Project

Tuesday, June 2, 1998 | 9:46 a.m.

The proposed repository at Yucca Mountain would resemble a large mining operation.

According to the Department of Energy, surface facilities would include an 80-acre north portal where nuclear waste would be received and packaged for burial; a 12-acre south portal area to house support facilities such as maintenance and security; a 3- to 4-acre emplacement shaft area that would provide the ventilation exhaust fans and maintenance support; and a half-acre development shaft area with a facility to house the intake fans and emergency hoisting system.

DOE spokesmen say the actual burial site, with tunnels, would cover about 1,400 acres deep underground. The waste would be stored in an emplacement block that spans 740 acres. It would be at least 600 feet below the surface and at least 330 feet above the water table.

Canisters containing the waste would be placed inside holes in the rock floors. A heavy shield then would be used to plug the hole.

According to a DOE report, the facility would be monitored for 50 years. Eventually the repository tunnels and shafts would be filled and sealed. The surface facilities would be removed and the site would be returned to its original condition, the DOE said.

About nuclear waste

The high-level nuclear waste to be stored at Yucca Mountain primarily would consist of spent fuel -- solid pellets of uranium the size of a pencil eraser. One pellet contains the energy equivalent of almost one ton of coal. The spent fuel is being stored in pools of water at nuclear power plants where it's generated, but that is only a temporary solution, DOE scientists say.

When in their useful state, the uranium pellets are sealed in 12-foot-long steel rods that are placed inside a nuclear reactor. After the uranium has generated enough heat to boil water for creating electricity in reactors, it no longer splits its atoms efficiently. About one-fourth to one-third of the total fuel load is "spent" and removed from the reactor every year. The spent fuel is highly radioactive.

Spent fuel can be hazardous because of high radiation levels and the remote possibility of a self-sustained splitting of the atoms of uranium and plutonium. This would not mean a nuclear explosion, but the resulting radiation would pollute the surrounding earth, water and air.

Strict control materials, such as boron, are required to be placed inside waste containers to prevent such an event.

The repository also would store nuclear waste from the Defense Department. Liquid waste from weapons facilities, which is not supposed to be buried, would first be turned into solid glass blocks or hardened in ceramic for storage in the repository.

Radiation hazards

The Nuclear Waste Policy Act of 1982 set guidelines for radiation exposure from a high-level repository, but Congress is considering lowering the standards. The amount of allowable exposure would go from 5 millirem (half the amount of radiation received in a single chest X-ray) to 100 millirem per year.

Opponents of a repository at Yucca Mountain say it's just another way of minimizing concerns about the site.

The Environmental Protection Agency, which sets the standards by law, is reviewing the proposed changes. The EPA had set a cap of 15 millirem per year for the low-level Waste Isolation Pilot Plant in New Mexico.

The DOE says the average American's annual dose of natural and manmade radiation is about 360 millirem per year. According to one DOE report, the repository would add less than 1 millirem to the radiation received by people who live about three miles from Yucca Mountain. The report notes that background radiation in Las Vegas is 59 millirem per year.

Opponents of the repository say 100 millirem would dramatically increase the level of exposure to normal doses of radiation and would increase risks of cancer. They are concerned also about radiation seeping into the water table.