Nuclear Energy and Waste


The Yucca Mountain Project

The Yucca Mountain Project originated from the 1982 Nuclear Waste Policy Act, “to provide for the development of repositories for the disposal of high-level radioactive waste and spent nuclear fuel, to establish a program of research, development, and demonstration regarding the disposal of high-level radioactive waste and spent nuclear fuel, and for other purposes.” After more than 20 years of scientific and engineering investigations, the Department of Energy (DOE) submitted a license application (LA) to the Nuclear Regulatory Commission (NRC) on June 3, 2008 for repository construction at Yucca Mountain.

The Yucca Mountain site is located about 120 km northwest of Las Vegas in a semi-arid region. The geology of Yucca Mountain is primarily fractured volcanic tuffs that vary in degree of welding. The repository at Yucca Mountain was planned to be located about 350 m below ground surface, within a thick unsaturated zone (UZ) above the water table. The safe performance of a high-level nuclear waste repository hinges on the multiple-barrier concept—namely, that the natural system and the engineered system would each contribute significantly to preventing radionuclides from leaving the repository and entering the biosphere.

LBNL was responsible for the site characterization studies aimed at understanding the barrier function of the UZ. During the period from 1997 through 2010, studies by Berkeley scientists focused on hydrological (seepage and transport) and thermal-hydrological-chemical coupled-process testing and modeling at Yucca Mountain’s Exploratory Studies Facility (ESF). The ESF consisted of an 8 km long, 8 m diameter underground tunnel with niches and alcoves for testing; and a smaller tunnel, the 2.7 km long, 5 m diameter Enhanced Characterization Repository Block (ECRB). In addition, a total of about 60 deep surface boreholes were drilled in the area providing geological, hydrological, and geochemical data. The testing and modeling program addresses some of the most compelling issues affecting the performance of a repository at Yucca Mountain, including:

  • How much water percolates through the UZ to the repository at Yucca Mountain?
  • What fraction of the water flows in fractures and what fraction flows through the rock matrix blocks?
  • What do mineralogical and geochemical data reveal about the past and current water distribution?
  • How much of this water will seep into the emplacement drifts (tunnels)?
  • How will the radionuclide migration from the repository to the water table be retarded?
  • How will coupled TH (thermal-hydrological), THC (thermal-hydrological-chemical), and
  • THM (thermal-hydrological-mechanical) processes affect flow and transport?

To address these questions, this project was organized into the following groups, with support from geophysical studies: