Scientist casts doubt on Yucca

Wednesday, Nov. 15, 2000 | 11:22 a.m.

RENO -- A Nuclear Regulatory Commission consultant cast doubt Tuesday on the geologic safety of a proposed high-level nuclear waste repository at Yucca Mountain.

Mary Beth Gray, an independent scientist from Bucknell University in Lewisburg, Pa., said she has discovered evidence in one of four types of earthquake faults at Yucca Mountain in which minerals were deposited by a significant amount of water.

The finding could contradict federal claims that any ground water in Yucca Mountain within the past million years was deposited by rain and not hot water rising from deep beneath the mountain.

Yucca Mountain, 90 miles northwest of Las Vegas, is the only site being studied for a repository for 77,000 tons of spent fuel from nuclear power plants and defense waste. The Nuclear Regulatory Commission would have the final say on whether a repository would be allowed to open.

Gray's work is important in the decision to license Yucca Mountain, NRC geologist Bret Leslie said.

If flooding of the repository by hot ground water occurred in the past 10,000 years, that raises the possibility that the site could flood again during the lifetime of the repository, he said. Such a flood could corrode the casks holding waste and release dangerous levels of radiation into the environment.

Gray's research keeps the question of possible flooding open, Leslie said, despite a report released earlier Tuesday by a UNLV scientific team led by Jean Cline and Nicholas Wilson that found the mountain is dry enough for a repository.

Cline and Wilson's work, which centered on dating samples to determine how long ago water invaded the mountain, showed that no water from deep within the earth had entered the repository area in more than 2 million years.

Gray looked at four types of faults and found one type that had not been studied by federal scientists. That type, called a Type B fault, contained calcite deposits that could have been left by hot underground water.

"The features in the faults don't support a trickle," Gray said after her presentation Tuesday afternoon at the Geological Society of America meeting this week.

Gray said she had not dated the mineral, so it could have been deposited yesterday or millions of years ago.

Gray urged the Department of Energy, which would build the world's first high-level nuclear waste repository at Yucca Mountain by 2010 if it is approved, to conduct further research on the calcite found in the faults.

The DOE has not addressed the mineral found in the complex faults, Gray said.

A Russian scientist working for the state of Nevada also reported evidence Tuesday that calls into question the suitability of a repository at Yucca Mountain and questioned Cline's findings in the UNLV study.

Yuri Dublyansky of the Russian Academy of Sciences said he found evidence that hot, deep water had invaded the repository site, 1,000 feet beneath Yucca's surface, in recent geological history.

Dublyansky, who now works for the state Nuclear Projects Office, said he found the mineral fluorite within calcite mineral layers that are only thousands of years old. Such deposits would indicate that water has invaded the site from below within the past hundreds of thousands of years, he said.

A congressional mandate in 1987 required scientists to determine whether geothermal water had entered the area in the past 1.5 million years.

During a lengthy debate with USGS and other scientists, Dublyansky said he had not followed the strict requirements set by the DOE for collecting his 40 mineral samples and had not recorded temperatures at his collection sites.

The USGS, like UNLV, has not found any indication that fluorite from deep water entered the repository in 9 million years, USGS scientist James Paces said.

UNLV, USGS and the state teamed up more than a year ago to study the 1983 theory of former DOE geologist Jerry Szymanski, who said that hot, deep water rises into the repository periodically.

The UNLV team collected 155 samples of Yucca's minerals throughout the 5-mile-long tunnel dug by the DOE to explore the mountain. Those samples were carefully cut, prepared and shared with the USGS and the state scientists.

UNLV's Wilson said he had found no evidence, even under the most sensitive microscopic probe provided by $1.4 million in DOE funds, that fluorite existed in Yucca's younger layers of rock.

Szymanski's theory was rejected by most scientists until Dublyansky presented new evidence in the mid-1990s that prompted the DOE to commission the UNLV study.