Wednesday, February 23, 2005
Copyright © Las Vegas Review-Journal

NATIONAL ACADEMY OF SCIENCES: Yucca safety discussed

Experts talk about the challenge of predicting the distant future

WASHINGTON -- The National Academy of Sciences delved into Yucca Mountain safety Tuesday when scientists discussed the uncertainties of predicting how the proposed nuclear waste repository might perform over tens of thousands of years.

The discussion before the academy's nuclear waste management board was watched closely by officials from federal agencies that will set standards for the project the Energy Department wants to build in Nevada.

The session aimed to explore a major Yucca Mountain question: How much confidence can decision-makers have in repository studies that purport to measure health and safety far into the future?

"Is it responsible to construct a waste repository with our present knowledge?" asked Klaus Kuhn, a climate scientist who sits on the academy board.

Leonard Konikow, a hydrogeologist with the U.S. Geological Survey, cautioned against overrelying on complex computer models that are attempting to predict Yucca Mountain safety far into the future.

Konikow said modeling errors can slant conclusions of the repository's performance.

The errors could be magnified in predictions of whether the mountain can safely contain nuclear materials 10,000 years or longer, Konikow said.

"We have to wonder if we are making predictions 10,000 years, 100,000 years into the future, are the error bands so wide so far out into the future as to make use of these models meaningless," he said.

"There is value to using the models but we have to be careful," Konikow said. "They are the single best tool we have in making predictions but you just can't have the same degree of faith in a 10,000-year prediction as you can in a one-year prediction."

The discussion took place as the Environmental Protection Agency rewrites standards that would require scientists to show that Yucca Mountain can safely contain highly radioactive materials for periods well beyond 10,000 years.

Officials from the EPA and the Nuclear Regulatory Commission, which will regulate repository operations, attended but did not speak.

Henry Pollack, a geophysics professor at the University of Michigan who delivered a presentation, said policy-makers should not be deterred by uncertainty, which he said "can never be fully eliminated."

"Waiting until uncertainty is eliminated before making important decisions is generally impossible," he said. "Unanswered questions should not lead to policy paralysis.

"My vision of a policy is one that gets started in the face of uncertainty," Pollack said.

Pollack said the government should anticipate "mid-course corrections." He said DOE should monitor the repository during construction and beyond for "surprises."

"There will be something that will happen in the nature of a surprise," Konikow said. "You hope it is not a catastrophic surprise."