The U.S. Department of Energy has filed a formal application to construct a nuclear-waste repository at Nevada’s Yucca Mountain. The application, which runs tens of thousands of pages, attempts to prove that 77,000 tons of nuclear waste could be stored at Yucca Mountain without harming public health, safety, and the environment for up to a million years. The Nuclear Regulatory Commission will have three to four years to decide if it’s convinced. President Bush gave his blessing to Yucca Mountain six years ago, and more than $6 billion has already been spent on research and engineering. But the much-delayed project has encountered strong public opposition; the state of Nevada plans to file as many as 500 contentions against the application. Sens. Barack Obama and Hillary Clinton have both said they would withdraw the application if elected president; Sen. John McCain has said he would move forward with it.