nuclear-news

For decades, the federal government has been floundering over what to do with the cylinders. They’re too hot to be easily housed with other waste. And the government’s quest to create a single permanent burial ground for all the nation’s high-level nuclear waste, from both military and civilian activities, is in disarray

Now, a deceptively simple-sounding solution is emerging: Stick the cylinders in a very deep hole. The approach, known as deep borehole disposal, involves punching a 43-centimeter-wide hole 5 kilometers into hard rock in Earth’s crust. Engineers would then fill the deepest 2 kilometers with waste canisters, plug up the rest with concrete and clay, and leave the waste to quietly decay.

The idea has been around for decades, but not long ago scientists had all but abandoned it. Over the past 5 years, however, as improved drilling technologies converged with the political and technical woes bedeviling other nuclear waste solutions, boreholes have regained their allure. DOE has gone from spending almost nothing on borehole research to planning a full-scale field test, costing at least $80 million. And earlier this year U.S. Energy Secretary Ernest Moniz gave boreholes a dash of publicity during a major speech, mentioning them as a promising way to deal with the cesium and strontium waste at DOE’s Hanford Site nuclear complex.

Boreholes have “been plan B and just missed the boat for years,” says nuclear engineer Michael Driscoll, a retired professor from the Massachusetts Institute of Technology (MIT) in Cambridge and one of the concept’s leading advocates. “Maybe now is the time.”

Many nuclear waste veterans, however, are skeptical. The technical challenges are daunting, they argue, and boreholes won’t end political opposition to building new nuclear waste facilities. “The borehole thing to me is a red herring,” says attorney Geoff Fettus of the Natural Resources Defense Council (NRDC) in Washington, D.C., which supports underground disposal in a shallower mine, but has sued DOE over now abandoned plans to bury the waste inside Nevada’s Yucca Mountain……..

This past March, a White House policy shift opened the door further. Moniz announced that the Obama administration would abandon previous plans to put all high-level waste in one spot and instead would seek separate sites for disposing of commercial nuclear waste—about 85% of the total—and military waste. Moniz called some of the defense waste, including Hanford’s radioactive cylinders, “ideal candidates for deep borehole disposal.”………

Yet borehole disposal is not as straightforward as it might seem. The Nuclear Waste Technical Review Board, an independent panel that advises DOE, notes a litany of potential problems: No one has drilled holes this big 5 kilometers into solid rock. If a hole isn’t smooth and straight, a liner could be hard to install, and waste containers could get stuck. It’s tricky to see flaws like fractures in rock 5 kilometers down. Once waste is buried, it would be hard to get it back (an option federal regulations now require). And methods for plugging the holes haven’t been sufficiently tested. “These are all pretty daunting technical challenges,” says the board’s chair, geologist Rod Ewing, of Stanford University in Palo Alto, California.

Even if those technical problems are surmounted, boreholes might solve only a fraction of the nation’s waste problem. That’s because much of the high-level waste simply wouldn’t fit down a hole without extensive repackaging. “Due to the physical dimensions of much of the used nuclear fuel, it is not presently considered to be as good of a candidate [for borehole disposal] as the smaller waste forms,” said William Boyle, director of DOE’s Office of Used Nuclear Fuel Disposition Research and Development, in a statement to Science. Spent fuel rods from commercial power reactors, for instance, are often bundled into casks that are about 2 meters across.

Then there’s the same problem that dogged Yucca Mountain: the politics of finding a place to drill the holes. “Let’s just assume [boreholes] could work better than anybody ever imagined,” says Fettus, the NRDC attorney. “You still wouldn’t solve the nut that everyone has been unable to solve”: persuading state and local governments to take on waste from across the nation………

Other nations with nuclear waste, including China, are watching. But, for now, the United States is the only country getting ready to drill. “Nobody else has stepped forward,” says Geoff Freeze, a nuclear engineer at Sandia who is overseeing the U.S. experiment. “It kind of fell to us.” http://science.sciencemag.org/content/349/6244/132.full