If water reaches the buried packages, it could react with container materials, causing corrosion and allowing radiation to escape into the environment before 10,000 years. However, the DOE believes heat from the buried wastes will drive water away from the containers. Chlorine-36, a byproduct of atomic weapons explosions in the Pacific Ocean in the early 1950s as well as a naturally occurring element, was found in soil samples taken at the repository level, raising concern about the speed of water movement through the mountain. The report notes the chlorine evidence is in dispute and is undergoing further study by other DOE scientists. Rainfall at the proposed desert repository averages about 7.5 inches a year.
Monsoons coming every three to seven years can add almost a foot of water to the mountain's surface.
The DOE estimates that rainfall, infiltrating the mountain at about 0.18 of an inch a year in normal conditions, could jump to 0.48 inches during monsoon rains. A similar amount and range of infiltration would occur during a glacial period, possible some time beyond 2,000 years from now. The current water table is about 3,400 feet below the surface of Yucca Mountain. The repository level is about 1,000 feet above the water table. A nuclear waste canister could be buried about 690 feet above the current water table if a repository spaced the waste farther apart to keep the rock cool.