Study: Hot water hasn’t invaded site in eons

Friday, Feb. 9, 2001 | 11:31 a.m.

Experts have concluded after a two-year study that hot water has not invaded Yucca Mountain in 2 million years, answering at least one scientific question about the safety of using the site as a high-level nuclear waste repository.

If scientists had proven hot water had flooded into the mountain within a million years, the plan to store the nation's radioactive waste in Nevada could have been in jeopardy.

Although other studies are pending that could disqualify Yucca Mountain as a site for the repository, Thursday's announcement puts to rest one question that has been lingering for more than 15 years and removes one impediment to the project's approval, scientists said.

The findings disappointed state officials who have been fighting the project, said Robert Loux, director of the Nevada Agency for Nuclear Projects.

"Obviously, we are disappointed that ages of minerals were not discovered that would disqualify the site immediately," Loux said. "The question remains about what was happening inside the mountain 5 (million) or 6 million years ago."

Lead scientist Jean Cline of UNLV said on Thursday that minerals in roughly half of the 155 rock samples collected throughout the mountain, 90 miles northwest of Las Vegas, indicated the presence of fluids ranging from 113 to 141 degrees Fahrenheit more than 2 million years ago, well below the boiling point of 212 degrees Fahrenheit.

Those temperatures do not indicate that geothermal water left calcite in cracks and crevices inside Yucca Mountain, she said.

"We have answered all of the questions, and the data are not ambiguous," Cline said.

The UNLV study did not answer the question of whether the mountain is safe from volcanic eruptions that could crush buried nuclear waste containers, releasing radiation into the air and ground water, she said.

The study also does not answer how long the layered metal containers will last in the mountain or how fast radiation could escape.

Other studies are looking at those questions. The Energy Department and scientists working for Nevada and the Nuclear Regulatory Commission, which must license a repository, have raised doubts surrounding the mountain's volcanic and seismic activity as well rapid water flow through its rocks.

Loux said the hot water study added important information to what was going on inside the mountain after it formed 12 million years ago and neither the DOE nor licensing regulators can ignore it.

The UNLV team's conclusion contradicts a theory by a Russian scientist, hired by Nevada, who believes hot, deep water flooded the mountain and left mineral deposits, making the Yucca site unsafe for nuclear waste disposal.

Yuri Dublyansky compared his theory of gushing hot water to geysers at Yellowstone National Park. Yellowstone is geologically young at 700,000 years and still active.

"Yucca Mountain is not Yellowstone," Cline said. "Yuri goes far beyond the bounds of the study and the topic."

The team's findings at Yucca Mountain are significant, she said, because they agree with earlier evidence collected by the U.S. Geological Survey indicating that hot water has not flooded the repository site.

Instead, the evidence from the latest study, which will be published in late March, points to minerals built in layers after rainwater had dried up at the bottom of cavities throughout the mountain.

USGS geochemist Joe Whelan, a team member, said that after nearby volcanos erupted more than 12 million years ago, it took 6 million years for the ash forming Yucca Mountain to cool down, allowing rainwater entering Yucca's earthquake faults to deposit calcite containing bubbles of water and gas known as fluid inclusions.

If hot water from deep in the mountain had flooded the repository, scientists would find calcite deposits on the ceilings and sides of those cavities, Whelan said.

But Dublyansky of the Russian Academy of Sciences Siberian Branch said he believes water rising from deep under the mountain deposited minerals indicating the site is unsafe to keep 77,000 tons of highly radioactive waste safe for at least 10,000 years.

Water temperatures cannot be explained from surface fluids trickling into the mountain, Dublyansky said, basing his theory on former DOE scientist Jerry Szymanski, who worked at the mountain 20 years ago. Szymanski posed the theory of water rising periodically into the mountain, making it unsafe to store radioactive waste.

The DOE spent $1.4 million to allow the UNLV team to answer the question of whether water hotter than the mountain's rock had ever been present in Yucca Mountain.

Geochemical expert Robert Bodnar of Virginia Polytechnical Institute, who acted as the team's consultant, said there was no evidence indicating that deep water such as that forming the geysers at Yellowstone ever reached Yucca Mountain.