Water damage sparks Yucca worries

Friday, April 6, 2001 | 11:20 a.m.

Areas inside the exploratory tunnel at Yucca Mountain that were sealed off for six months developed so much moisture that electrical test equipment in the rooms shorted out, losing valuable data, a Nuclear Regulatory Commission report shows.

Yucca Mountain, 90 miles northwest of Las Vegas, is the only site being studied to bury 77,000 tons of nuclear reactor and weapons waste. Water is a concern there because the area's mineral-laden ground water could corrode containers holding the waste, releasing radioactivity into the environment.

If the moisture in the tunnel is found to be ground water, the dump project would be in jeopardy.

Federal scientists believe if the moisture is from condensation, it would be harmless. State scientists note, however, that even condensation, if it contains minerals from Yucca Mountain's rock, could be corrosive.

The Energy Department is expected to recommend the site later this year as the world's first high-level nuclear waste repository.

The three research areas were dug out along the 5-mile-long tunnel, which is near the surface, and equipped with probes to measure water inside the rock. They were sealed last August to prevent the dry outside air from entering, to simulate what the mountain was like before the tunnel was excavated.

By September scientists realized that the equipment's electricity had failed, including the backup battery power. When they reopened the research rooms in January, they found electrical shorts that appeared to be caused by excessive water.

It was one of several studies focused on finding out the path of ground water through the mountain, which is made primarily of layered volcanic ash. If water has invaded the repository level, 1,000 feet below the surface, within the past 10,000 years, the site could be disqualified as a repository.

The water table at Yucca Mountain is 1,000 feet lower than the site.

So far, none of the studies has definitively shown a problem, but none has ruled out dangerous levels of moisture either.

The report on the failed experiment was included in monthly reports of the NRC's on-site scientists, who are overseeing work by the Energy Department.

The DOE is charged with studying and, if it is found safe, building the repository. The NRC would have to license it before it could open.

DOE researchers reported to the NRC scientists that they had been unable to collect 75 percent of the data they sought on water at the three sites because of power outages in the hundreds of probes.

Humidity levels inside the alcoves jumped above 90 percent last summer, DOE scientists said.

The DOE suspected steamy conditions inside the alcoves had disrupted electrical connections to the probes monitoring the mountain. Although batteries backed up conventional power lines, their supply lasted only about two weeks.

The DOE opened the bulkheads in January, dried the air, better insulated the electronics, then resealed areas. The water monitoring project is expected to continue throughout this year, DOE spokeswoman Gayle Fisher said.

Power was restored to the monitors, but conditions inside the mountain have not returned to normal, according to NRC's technical staff. "They have a ways to go yet," Chad Glenn of the NRC's Las Vegas office, said this week.

The amount of moisture inside the mountain already has raised questions from independent scientists serving on the Nuclear Waste Technical Review Board. At a February meeting in Amargosa Valley, the scientists questioned DOE representatives closely about "soaked" drip cloths hanging inside the alcoves.

The scientific panel urged the DOE to chemically analyze the water found on the cloths to determine if it came from condensation or from moisture flowing through the mountain's rocks.

Scientists working for the state of Nevada, which opposes the repository project, are concerned with the lack of information provided after the DOE's power outages.

Water -- even condensation -- could create a film on the metal surfaces of waste containers and shields, causing chemical reactions, said Susan Zimmerman, technical program administrator for the state's Agency for Nuclear Projects. Heat from the buried waste could enhance the chances for such reactions, and the consequences are anyone's guess, she said.

The DOE has been studying Yucca Mountain since 1983. By the mid-1990s scientists discovered more water than expected in the rock.

Engineers now are suggesting multiple barriers to protect people and the environment from escaping radioactivity.

Those barriers include waste packages still being designed, titanium shields to deflect ground water from dripping on the packages and a filler to seal the mountain in 50, 100 or 150 years.

The additional protection against moisture is expected to increase the cost of the dump, which is currently estimated to be about $60 billion.