Radioactive chlorine stirs Yucca controversy

Tuesday, May 2, 2000 | 11:08 a.m.

Two government scientists disagreed publicly Monday on whether atomic bomb fallout reached inside Yucca Mountain, a critical issue that could indicate whether underground water poses a threat to a proposed high-level nuclear waste repository.

Radioactive chlorine was discovered deep in the rock of Yucca Mountain, 90 miles northwest of Las Vegas, 15 years ago, and since then scientists have been trying to determine where the radioactivity originated.

For if the contamination is from 1950s Pacific island nuclear bomb tests that fell in rain on Yucca Mountain and flowed through rock fractures, as Los Alamos National Laboratory scientists say, then the Department of Energy has a big problem.

According to the DOE's own rules, if scientists discover water traveling through Yucca faster than 1,000 years, it could disqualify the site as a nuclear waste repository. Yucca Mountain is the only site under study by the DOE to bury 77,000 tons of highly radioactive wastes.

A competing Lawrence Livermore National Laboratory scientist, who received preliminary results a week ago, countered during a scientific review board meeting in Pahrump on Monday that there is no evidence of radioactive fallout in the mountain.

Livermore researcher Marc Caffee, who is working with a U.S. Geological Survey team, said that his research shows the chlorine-36 found inside Yucca is at least 300,000 years old and probably comes from cosmic rays or uranium found naturally in the volcanic rock.

If the chlorine inside Yucca is found to be from the atomic fallout, that would be strong evidence that water flows rapidly through the volcanic layers, members of the independent review board said.

"This stuff really zips through the mountain," board member Norman Christensen said.

"It's an important issue because earlier results show there is fast flow and new research doesn't show it," said Jared Cohon, chairman of the Nuclear Waste Technical Review Board.

June Fabryka-Martin of the Los Alamos National Laboratory in New Mexico began conducting chlorine-36 fallout studies at Yucca in 1990. Her team collected 52 rock samples from fractures and faults along two miles of the tunnel inside the mountain.

The atomic fallout left its fingerprints inside the tunnel, she said. Earlier studies below the repository location in the mid-1980s showed tritium and chlorine-36, both traced to radioactive fallout, she said.

Caffee said that his "surprising" results showing no evidence of fallout came from samples taken inside the DOE's exploratory tunnel along the Sundance Fault, which follows the northwest side of Yucca Mountain. "But that doesn't mean the chlorine-36 (from bomb fallout) isn't there, because we have more analysis to do," he said.

While Los Alamos sent its samples to other laboratories for analysis, Livermore tested its own 50 samples.

"We're both pretty baffled," Fabryka-Martin said.

As a first step, the review board, appointed by Congress in 1987 after Yucca was singled out for investigation as a nuclear waste repository site, urged another round of studies by both labs sharing the same samples.

Russ Dyer, the DOE's Yucca Mountain Project manager, promised to conduct the necessary studies, even if Congress trims more than $100 million out of the department's request for $437.5 million next year. "We may be seeing a little bit of a fast path," he said. It is too soon to estimate how much the extra studies will cost, he said.

Radiation moving within the mountain is not new, UNLV hydrologist Earle Dixon told board members. The DOE discovered that plutonium moved in ground water almost a mile at the Nevada Test Site on particles called colloids.

Dixon said he wondered why the DOE isn't concerned about the radiation from 928 bombs exploded at the Nevada Test Site, just uphill from Yucca, and why the site was not on the Environmental Protection Agency's Superfund list of toxic locations for environmental cleanup.

"Maybe because it would jeopardize Yucca Mountain?" Dixon asked. No one at the meeting could answer his question.

Mary Manning covers environmental issues for the Sun. She can be reached at (702) 259-4065 or by e-mail at manning@lasvegassun.com