Yucca Mountain proposal is staggering
A graveyard for nuclear waste
The Associated Press
THE ASSOCIATED PRESS
LAS VEGAS - Scientists are designing a system of tunnels with the best possible chance of safely entombing high-level nuclear waste inside Yucca Mountain for 10,000 years.
Yucca Mountain Project scientists are looking far into the future to anticipate how geological conditions could change, a process they call "design evolution," to develop their repository design, the Las Vegas Review-Journal reported yesterday.
Located about 90 miles northwest of Las Vegas, Yucca Mountain is the only site being studied to entomb 77,000 tons of the nation's high-level nuclear waste, mostly metal rods containing spent fuel pellets from commercial power reactors.
Of key importance will be taking into account surface water that could trickle down through cracks in the volcanic-rock ridge, potentially corroding waste canisters. Scientists must also calculate how far apart packages of the decaying, radioactive waste must be spaced so the repository can operate at a cool enough temperature to avoid triggering unpredictable water movement in the rock.
The scientists are trying to convince an independent, presidentially appointed panel of experts that the highly radioactive waste can be safely contained in the mountain by keeping it cool enough and dry enough for at least 10 millenniums.
That will be done, they say, in a maze of tunnels up to 100 miles long, 1,000 feet beneath the crest of the flattop ridge.
The conceptual design will be part of a report that the Energy Department secretary will review to determine whether the site is safe for storing the waste.
Geologists consulting for the state of Nevada have been critical of the mountain's natural setting. They contend hot ground water from beneath the repository could shoot upward, loading the waste caverns with thermal water laced with radioactive materials.
Federal scientists disagree and say the evidence from minerals inside the mountain means the greatest threat from water is in it percolating down from the surface of the ridge.
To prevent a disastrous situation, the federal team must forecast what mix of metals surrounding the ceramic nuclear fuel pellets will withstand corrosion the longest, even though rainfall and climate conditions or earthquakes and volcanic activity can't be predicted.
Last month, the 11-member panel of Clinton appointees, known as the Nuclear Waste Technical Review Board, expressed concern that the designs presented so far by the Energy Department could create problems. One problem could occur if the waste heats the rock to a temperature of 300 degrees Fahrenheit, causing water to move inside the mountain.
Water boils at 205 degrees at the repository's elevation.
The panel, which makes recommendations to Congress and the Energy secretary on the technical aspects of the proposed repository, offered a suggestion to the designers.
"We asked DOE to look at a cooler design to compare with the hot design," explained one engineer on the board's staff, Carl Di Bella.
A "cooler" design - one that lets decaying waste heat up surrounding rock walls to about 180 degrees, or 25 degrees less than water's boiling point - would give the panel more confidence that water inside the mountain won't rapidly corrode waste canisters and carry off potentially deadly radioactive materials.
Yucca Mountain Project nuclear engineer Dan Kane said Energy Department scientists are drawing up plans that he expects will satisfy the panel's concerns.
"We have studied - among other things - a hot repository design, a moderate temperature design and a cool design," Kane said.
If the site is found to be suitable for safely containing waste - based in part on a recommendation from the Energy secretary expected this year or next - and the Nuclear Regulatory Commission deems the design fit for licensing, plans call for the first spent fuel rods to be entombed in 2010 with closure of the repository in 2060. The process could be delayed by other issues.
The Department of Energy's inspector general is investigating whether its employees or contractors have been biased during the site selection process.
Nevada's congressional delegation also has asked the General Accounting Office to investigate charges that the Yucca Mountain site has been mismanaged.