It’s been eons in the making, features a cast of thousands and cost in the billions.
It is Yucca Mountain, the proposed geologic repository in Nevada for high-level radioactive waste.
Few would argue that, geologically, it is among the most studied pieces of real estate on the planet.
Much of the most significant research from the last 20 years has been gathered in The Geology and Climatology of Yucca Mountain and Vicinity, Southern Nevada and California, published this spring by the Geological Society of America.
The study was conducted by the U.S. Geological Survey and U.S. Department of Energy National Laboratories. It covers the mountain’s tectonic setting and detailed structural geology and stratigraphy, plus the climate history and potential climate change that could affect the site’s ability to keep radioactive waste safely contained.
While the ultimate decision of whether the repository ever becomes reality rests in the political realm, the proposal is sound geologically, said John Stuckless, who co-edited the book with Robert A. Levich. Stuckless has worked on the USGS Yucca Mountain Project since 1986.
“You’re never going to find a ‘perfect’ site,” Stuckless said, but “from an earth science perspective,” the plan will work, he said.
Quick to state that the USGS never endorsed the project, Stuckless said years of research indicates nuclear waste stored at the site never would be transported accidentally to the surface or into the water table.
A series of large volcanic eruptions formed Yucca Mountain 11 million to 15 million years ago, Stuckless said. It consists of layers of ignibrite, or welded tuff and semi-welded and non-welded tuff. The repository zone is densely welded tuff 1,000 feet below the surface and 1,000 feet above the water table, Stuckless said.
Bounded by two normal faults, the formation tilts to the east.
“If anything, being in a unsaturated zone was an advantage,” he said, “because the waste has to be retrievable for 300 years.”
It’s also supposed to remain safely entombed for up to a million years, according to the legislation dealing with the site.
Chances of seismic or volcanic disruption of the region are considered extremely unlikely, researchers say.
That leaves as the main concern the cracks and fissures that could provide a pathway for radioactive waste to find its way into the water table.
To address those concerns, the mountain has been scrutinized at resolutions up to 1-to-250, Stuckless said.
“Every fracture larger than a meter has been recorded,” he said. “We have a 750,000-year record of history on one fault.”
Findings presented in the book are the results of “fairly standard geological techniques,” Stuckless said.
“The larger problem is that we’ve never really studied unsaturated zones ... what happens there,” he added.
A second volume, expected to be ready by year’s end, focuses on hydrology and geochemistry and will include more of the new technologies applied to the study.
How ’Bout This Weather?
If the geological premise for the project is sound, what other factors could conceivably pose risks?
Climate change is one possibility that has been researched.
The region has experienced much wetter climates in the past, and could again, but most of the geologic research indicates slight chance of nuclear waste seeping into the water table.
Climatology examined in the book’s final chapter does little to weaken the case for Yucca Mountain as a storage facility, but could be significant in terms of the global warming debate, said Mike Campbell, chairman of AAPG’s Energy Minerals Division’s Uranium Committee.
While many believe man’s influence on global climate would be short-lived, some researchers postulate that the burning of fossil fuels could have profound effects arching over geological time periods, Campbell said.
Astronomical and orbital predictions support the notion that Earth already should be entering its next ice age. Some of the Yucca Mountain researchers, however, say it is possible that humans’ impact on climate could last up to 50,000 years and delay the glacial maximum for 100,000 years, he said.
Such predictions may heat up the global warming debate, but climate change should have little effect on the geology of Yucca Mountain.
“I believe the plan is a good one,” Campbell said, “especially after reading this material.”
Further On Down the Road
Over the decades since it was first proposed, the Yucca Mountain study “has kept a lot of people employed – thousands,” Stuckless said.
When USGS suggested the former nuclear testing site in 1976, it already had been the subject of 900 man-years of study, he said.
Besides geoscientists, the project involves a large engineering component, biospheric researchers and others, he said.
As an example of how much study has been devoted to the site, Stuckless noted that one chapter in the book lists more than 100 references going back some 20 years.
The prime contractor for the project, Bechtel SAIC, a consortium of government contractors, Bechtel Corp. and Science Applications International Corp., employs 1,300 people.
The DOE is expected to submit an application for a license to operate the facility next year. March 31, 2017, is the target date for opening the facility and when it would begin accepting waste.
If the project opens, utilities and defense facilities would begin shipping waste to the central depository from more than 120 local storage sites around the nation.
With the emphasis on storage rather than disposal, the nuclear industry may begin recycling the waste.
“I predict that within 20 years, it will be a natural resource again,” Campbell said.
“Transportation on highways will be a concern, but so much engineering has gone into the containers the risk is minimal,” Campbell said.
“We’ll see a period of well-meaning people lying across roads (to block shipments), but that will pass,” he said.
If any waste did leak from its man-made and geological tomb, the hazard would be slight, he said.
“Even if it did get out somehow, you’d fence off the area for 680 years,” Campbell added, “but it wouldn’t float in the air like Chernobyl.”
Yucca Mountain is a ridge line in south-central Nevada, about 100 miles northwest of Las Vegas. It is in a remote desert area on federally protected land inside the secure boundaries of the Nevada Test Site.
The proposed facility lies 1,000 feet below the surface and 1,000 feet above the water table. The main tunnel is U-shaped, five miles long and 25 feet wide.
Alcoves branching from the tunnel are used to stage experiments. Waste would be stored in smaller tunnels perpendicular to the main tunnel, which are yet to be drilled.
Waste would be sealed in multilayer stainless steel and nickel alloy containers covered by titanium drip shields.
More than $7 billion has been spent so far on the project. Total cost is expected to range from $50 billion to$100