The extensive shale deposits in the U.S. have been getting a lot of attention in recent years as technology has unlocked hydrocarbon deposits trapped in their rock strata – natural gas and natural gas liquids in the Mid-Atlantic states, gas in Texas, and crude oil (and lots of it) and gas in North Dakota. But could shale also be the answer to another major U.S. energy policy conundrum: the decades-long festering issue of what to do with U.S. nuclear waste?
Chris Neuzil, a U.S. Geological Survey scientist writing in the Bulletin of the Atomic Scientists last year, suggested that shale might make a great alternative to the volcanic tuff of the Yucca Mountain, Nev., site. Yucca Mountain now looks like a clear failure despite decades of development and billions of dollars of Department of Energy (and U.S. consumer) expenditures. Neuzil writes that while the doughty but low-key shale has recently surfaced in the context of oil and gas, it “may also offer something entirely different – the ability to safety and permanently house high-level nuclear waste.”
While the 1982 Nuclear Waste Policy Act called for examination of a large spread of geological rock and mineral formations – salt, granite, basalt, and tuff – “shale has never even had a cameo appearance in the U.S. waste program,” says Neuzil. “Yet the picture emerging from studies in Europe and elsewhere is that shale has unique attributes as a host rock.”
The key issue for underground storage of spent nuclear fuel – the definition of “high-level” waste – is water. “Predicting the wastes’ fate is much more difficult than any originally imagined,” says Neuzil, “in large part because of water.” Permeability of underground rocks can vary by many orders of magnitude. Congressional overseers in 1987, basing their conclusions on experts from the Department of Energy, gave Yucca Mountain the black spot as a repository in large part because they believed the strata deep within the mountain were dry. They were wrong, just as they were wrong in the 1970s when settling on salt deposits in Kansas for underground nuclear waste burial.
Yucca Mountain, underground, is so wet that DOE had to redesign the containers holding the nuke waste to shield them from water. That added billions to the cost of the already-costly waste dump. The fear is that water can carry radionuclides off of the waste site and into the general environment.
Shale formations, argues Neuzil, have a peculiar property that offers a way around the difficulty of determining if an underground site has water problems. Many of shale sites the geologists have studied – not necessarily for their suitability for nuke waste storage – have pressure “anomalies” that signal “that almost no groundwater is able to leak from the shale,” says Neuzil. “What’s more, pressure anomalies show that conditions have prevailed to tens to hundreds of thousands of years, because they take that long to form.”
All that, says Neuzil, means that “there is reason to believe that shale can isolate spent nuclear fuel underground as long as needed. Shale also has what amounts to built-in containment redundancies, including a tendency for clay particles to sorb, or grab, dissolved waste. Then there is the sheer abundance of shale, which greatly expands geographic options for repository siting, even when oil- and gas-rich or otherwise unsuitable formations are ruled out.”
None of Neuzil’s analysis addresses whether the politics of shifting to shale for nuke waste would be any less corrosive than the current controversy. That’s not his brief. Nonetheless, Neuzil’s analysis suggests the need for further examination. Shall it be shale?