Yucca Mountain study finds water in rock

More studies

While the Department of Energy has hundreds of studies under way at Yucca Mountain, major efforts in addition to ground water studies include:

Large and small heaters are warming up Yucca Mountain's tuff to see if it would crack if containers of hot radioactive wastes are buried there.

Scientists are analyzing what happens to the rock and soil exposed to radiation and heat from nuclear waste containers. Chemical changes of soils could speed corrosion of the containers.

Although the DOE believes the damage threat from an earthquake to a repository 1,000 feet beneath the surface of Yucca Mountain is remote, the agency still must prove nuclear waste would stay put after a 7.0 magnitude temblor.

Again, the DOE estimates that the chance for volcanic activity is slim, federal scientists have to convince the Nuclear Regulatory Commission that a nearby eruption would not disrupt the repository.

The DOE is designing both transportation and storage casks for a repository at Yucca Mountain. The casks for burial in the mountain must contain radioactive contents for a minimum of 300 years.

A UNLV-led research team has confirmed through crystals that water once flowed through the volcanic rock at Yucca Mountain, and the scientists now are turning their attention to finding out how long ago the water created the crystals, how hot the water probably was and where it came from.

Those answers will take at least until spring 2001 to find and could help determine whether the only site being studied as a dump for the nation's 77,000 tons of highly radioactive waste would be scientifically suitable, UNLV geologist Jean Cline said Tuesday.

If the water invaded Yucca Mountain within the past 2 million years, there could be problems with burying radioactive waste there, she said. Evidence of water that recently would mean that water could flow through the mountain again and corrode canisters holding the toxic waste, allowing radioactivity to escape in dangerous amounts.

The scientists don't expect to have definitive answers when they're done, but their results could raise a red flag on the safety of the project.

"I don't think we're going to find out that golden nugget that will tell us if Yucca Mountain will be safe to store nuclear waste," consultant Robert Bodnar, a water expert from Virginia Technical Institute, said. "We will have a better understanding, but we won't know everything."

The search for answers on whether the repository is scientifically feasible and safe has become a mini-industry.

In the Department of Energy's original plan, a high-level nuclear waste repository was supposed to be open at the site 90 miles northwest of Las Vegas by now at a cost of roughly $18 million. At this point it will be at least another decade before the first truckload rolls in -- if at all.

What DOE has put into the mountain is $13 billion worth of research -- almost equal to the annual gross domestic product of Cuba. The study by Cline and her colleagues is costing another $1.4 million, and several other studies are continuing on other factors that could affect the repository.

The scientific study is able to attract the DOE's money and buy the time, because if the United States builds a repository for highly radioactive waste, it would be the first nation in the world to do so. There are no others to learn from earlier mistakes.

With hundreds of studies it has commissioned, the DOE is trying to determine what would happen when Yucca Mountain's volcanic tuff is heated with buried casks filled with radioactive wastes, how fractures in the mountain would react to heat and water and how water flows through fractures in the tuff, among other things.

All of these results will become part of a computer simulation program to see how the mountain might react if highly radioactive material is buried deep within.

"I would not want to make that call," Cline said, adding that the study will give regulators and scientists more information to determine if Yucca Mountain is a safe place to bury the wastes or not.

"The concept is that if the mountain isn't the right place, we'll walk away from it, that's true," senior DOE technical adviser William Boyle said.

However, no single test result will stop the project, Boyle said. "I don't know of any single test that has a pass-fail grade." The key is what the cumulative test results tell investigators.

Probably the most critical questions for Yucca Mountain revolve around ground water below the desert floor, both DOE and state officials charged with oversight of the many studies agree.

DOE's Yucca Mountain Project Manager Russell Dyer said that answering the question of how fast water moves through the mountain is crucial to a repository's future.

"I think if there is evidence of ground water there within thousands of years, then Yucca Mountain will be dead," physicist Arjun Makhijani, director of the Institute for Energy and Environmental Research in Takoma, Md., said. He has independently reviewed DOE's studies. "If it's millions of years, then there will be no debate and a repository will go forward. If the number falls in between, then there will be a fight."

The temperature of the water is also important, because if it appears to have been hot, it would be evidence that geothermal water has risen from deep within the Earth up to the repository site. Similar events in the future could corrode waste canisters.

Rainwater seeping from the ground down into the repository poses a similar concern.

In addition, DOE and state officials want to know how fast ground water moves from one point to another, so they can try to predict whether radiation might escape the repository site through the water. Some evidence suggests that radioactivity from nuclear testing at the Nevada Test Site has traveled in water up to a mile from its original site.

The nearest farm is in Amargosa Valley 12 miles south of Yucca Mountain.

Several agencies with oversight on whether Yucca Mountain becomes a repository are keeping a close eye on the studies.

Robert Loux, executive director of the Nevada Agency for Nuclear Projects, believes Cline's study conclusions could halt the repository project if they substantiate geothermal water is rising in the mountain, which he believes it will.

"I think it's an important study," Loux said. "I think it means a great deal of trouble for the repository if the dates of those deposits are younger than 1 million years. I certainly think it could break the repository."

William Reamer, chief of the high-level nuclear waste branch for the Nuclear Regulatory Commission, would not speculate on what Cline's study or any other particular study means to Yucca Mountain.

"It is premature for the NRC to speculate if it would be a show-stopper," Reamer said. He notes that the theory of geothermal water periodically rising inside Yucca Mountain and invading the repository site has been studied and is not generally accepted.

The DOE is not expected to submit a license application to the Nuclear Regulatory Commission until at least 2001, at which time those questions would have to be answered, Reamer said.

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