Nature and engineering Working Together for a Safe Repository

If a repository were built at Yucca Mountain, it would rely on two distinct systems to prevent radioactive materials from escaping into the environment. These systems act as barriers to the movement of radionuclides. The first system involves natural barriers--the rocks, water, and climate at Yucca Mountain. The second system is comprised of an array of engineered, or man-made, barriers that give the repository defense in depth and add safety margins. These systems would work together to protect the public and the environment. The mountain's natural features present a formidable line of defense against possible movement by radionuclides. These barriers include Yucca Mountain's unique geology, the region's dry climate, and, in general, a range of enclosed water systems that should slow water that contains radioactive particles from reaching rivers or other groundwater systems. The mountain's natural barriers and planned man-made barriers should prevent most moisture from ever reaching the waste packages within a repository. Moreover, the natural barriers would slow the movement of radioactive particles that do dissolve in water. The engineering, or technological measures, that would be built into a repository at Yucca Mountain would help ensure that health and safety standards are maintained even if some components of the natural system do not perform as expected for the first 10,000 years of repository operation