The U.S. Geological Survey (USGS) said shale and other formations might be a safe place to dispose of nuclear waste, specifically spent nuclear fuel (SNF) currently being stored at nuclear power plants around the world.

In an article titled “Can Shale Safely Host U.S. Nuclear Waste?” published in Tuesday’s issue of Eos, a weekly magazine produced by the American Geophysical Union, USGS hydrologist Christopher Neuzil said shales and other argillaceous formations — mudrocks, clays and similar clay-rich formations — could provide a storage solution.

“They have low permeability,” Neuzil said. “Flowing groundwater transports dissolved material and is thought to be the most likely means by which nuclear waste in an underground repository could escape and contaminate the biosphere, posing a risk for future generations. Clay-rich geologic media are millions to tens of billions of times less permeable than productive aquifers and hydrocarbon reservoirs.

“Their exceptionally low permeability suggests that argillaceous formations could be effective geologic barriers to the migration of SNF and HLW [high-level nuclear waste] constituents from a repository. What’s more, argillaceous media are the most common and voluminous of sedimentary materials and often are found in relatively old and stable geologic settings. Thus, tectonically quiet sedimentary terrains with thick clay-rich sequences may have a number of desirable qualities for hosting America’s substantial and growing inventory of nuclear waste.”

According to the U.S. Government Accountability Office, about 70,000 metric tons of SNF are now in pool or dry cask storage at 75 sites across the United States.

The U.S. Department of Energy had planned to build a repository for SNF and HLW at Yucca Mountain, NV, but those plans were scrapped by the Obama administration in 2010.

In a statement Tuesday, the USGS said its scientists “have looked at several research efforts, including projects that are underway in France, Belgium and Switzerland to confirm that shale formations in those countries are favorable for hosting nuclear waste repositories.”

Neuzil added that “deciding how to safely dispose of SNF and other HLW is a very important issue that is not going to go away. Although shales and similar rocks have not been considered for hosting nuclear waste in the United States, recent research points to them as a very promising option.”