Washington

The US Senate's decision on 9 July to approve the proposed nuclear-waste repository at Yucca Mountain, Nevada, has set the stage for a fresh and exhaustive technical investigation of the plan.

The Department of Energy (DOE), which is running the project, must produce convincing data on hundreds of technical issues before starting to build the repository, in 2008 at the earliest.

The Nuclear Regulatory Commission (NRC), which must grant a licence before the project can begin, has a list of 293 separate topics that it wants answers on, officials there say. There remain “gaps in information” concerning the site's volcanic and seismic activity, hydrology and geology, as well as engineering issues, says Janet Schlueter, a branch chief at the NRC's Division of Waste Management.

Under the terms of the licence application, project managers have to satisfy the NRC that the repository will contain the waste safely for 10,000 years. And Schlueter stresses that the licensing process will not be a simple 'rubber stamp' — the NRC has a four-year window to interrogate the DOE over the proposal.

Energy undersecretary Robert Card says that the project team has collected data that will fulfil most of the NRC's requirements. “We've already resolved many of these issues,” he says. The department hopes to file its application by the end of 2004.

But “there are several issues where there is significant work to be done”, says George Hornberger, an environmental scientist at the University of Virginia and chairman of the NRC's Advisory Committee on Nuclear Waste. NRC officials have recently raised the possibility of volcanism at the site, says Hornberger. Both the DOE and the NRC are currently running computer simulations to address a disagreement about the risk posed by volcanic activity (see Nature 412, 850–852; 2001).

Other questions surround the deterioration of the sophisticated metal containers that would hold the waste, says Kevin Crowley, director of the Board on Radioactive Waste Management at the National Research Council. Project planners “need to understand how that metal will behave over thousands of years”, he says.

Hornberger is not convinced that the DOE will be able to complete its licence application by 2004. “They have a lot to do, and it's not going to be easy,” he says.