Scientists: Nuke waste containers unsafe

Friday, Dec. 13, 2002 | 11:09 a.m.

Metal containers designed to store high-level nuclear waste in a Yucca Mountain repository would dissolve, risking radiation release, scientists working for the state of Nevada said Thursday.

Materials corrosion expert Roger Staehle, a Minnesota consultant, and Don Shettel, a geochemistry and mineralogy expert, told the National Academy of Sciences Board of Radioactive Waste Management that metal alloys proposed by the Energy Department for use in a repository will not safely contain 77,000 tons of radioactive waste.

The National Academy panel meets periodically to discuss waste issues and analyzes Yucca Mountain work, but it has no direct authority over the project.

The board is interested in the Department of Energy's plans to use waste containers made of C-22, a metal alloy, to store the spent nuclear fuel. The waste containers would be placed in tunnels under Yucca, 90 miles northwest of Las Vegas. Plans also call for the use of tent-like titanium drip shields to be placed over the containers to protect them from water corrosion.

But the metals eventually will dissolve in heat and water conditions expected inside Yucca Mountain, the scientists say.

Staehle and Shettel studied heated water in laboratory experiments at Catholic University to test the two key metals proposed by the Energy Department.

A critical element of the Energy Department's plan for a Yucca Mountain repository requires the use of "engineered barriers" -- the waste containers and titanium shields. State officials have criticized the department for relying too heavily on the engineered barriers. The law requires that a national nuclear waste dump rely primarily on geologic barriers -- the mountain's rock structure -- to isolate the waste from the outside world.

By relying primarily on the engineered barriers, the Energy Department has essentially admitted that the mountain cannot safely isolate waste, state officials allege.

For their tests, Staehle and Shettel used an acid water solution that simulated Yucca Mountain water, heating it to temperatures between 158 degrees Fahrenheit to 293 degrees Fahrenheit.

The heat produced an acid vapor called "aqua regia," which is so potent it even dissolves gold, which is a resilient metal, said Bob Loux, Nevada Nuclear Projects Agency Executive Director.

As the vapor condenses and evaporates, it leaves a concentrated acid and solid particles behind. The solids attract more water vapor from the air and surrounding rock, forming stronger acids.

"No metal will last more than 500 to 1,000 years, particularly C-22," Loux said.

"These findings reinforce our belief that the U.S. Department of Energy and the Nuclear Regulatory Commission have long used fuzzy science to prop up their plans to dump the nation's nuclear waste in Nevada," Loux said.

The Nuclear Waste Technical Review Board, independent scientific review panel created by Congress that oversees DOE's Yucca Mountain work, also has expressed concern that federal scientists had not done enough tests on the metals.

Previous laboratory work by other state consultants showed that lead, mercury, fluorine and possibly other trace elements in the water and rock of Yucca Mountain would weaken the metals containing nuclear wastes.

"If the waste containers won't perform as DOE predicts, and the geology plays nearly no role in containing the waste, the site should be abandoned," Loux said.

Energy Department officials have dismissed the Nevada research, saying it did not accurately simulate Yucca conditions.

In a related matter, Nevada officials Thursday said they were eager to see the results of a General Accounting Office investigation of the risks of two scenarios: shipping waste to Yucca Mountain for permanent storage, and leaving the waste where it now sits, at power plants and Defense Department sites nationwide.

The GAO report was requested earlier this year by Rep. Joe Barton, R-Texas, a Yucca advocate. The GAO is the investigative arm of Congress.

Clark County Nuclear Waste Division director Irene Navis said GAO staffers have informed her that the study has been expanded to include study of the risks of terrorist attacks on waste shipments, as well as waste storage sites. The study is expected in February.

"The GAO assured us that the study will be comprehensive and extensive," Navis said.

Sun reporter

Benjamin Grove contributed to this report.