Experts at AAAS Capitol Hill Briefing See Problems with Nuclear Waste Plans

America’s effort to safely store radioactive wastes from nuclear power plants is behind schedule and plagued by technical uncertainties that may lead to even more delay and higher costs, experts said at a seminar in Washington, D.C., organized by AAAS’s Center for Science, Technology and Security Policy.

Allison Macfarlane, a Massachusetts Institute of Technology geologist, said at the 24 April seminar in the U.S. Capitol that the Department of Energy is at least four years behind schedule in applying for a license to begin building a geologic repository for nuclear waste at Yucca Mountain in Nevada.

She said the DOE was, by law, to have applied for a Yucca Mountain license from the Nuclear Regulatory Commission in 2002. Now she expects the license application to come in 2007 and the NRC will then have four years to act on that application.

“The earliest you could possibly see construction begin on the repository would be five years from now,” she told a packed room of journalists and Capitol Hill staffers. “I think it will be longer.”

But even if the Yucca Mountain nuclear repository is approved as now planned, it may not be spacious enough to store all the nuclear waste now accumulating in temporary storage facilities at the nation’s 103 nuclear reactors, said Macfarlane.

The current legislated capacity of Yucca Mountain is set at 70,000 metric tons. Macfarlane said a 2002 Department of Energy study estimated that the ultimate capacity of the under mountain storage would be about 119,000 metric tons and there is a bill in the U.S. Senate to expand the amount of land set aside for the repository land. But even that may not be enough, she said.

Macfarlane said that at the end of 2005, there were 52,000 metric tons of spent civilian nuclear fuel in the nation’s inventory. The accumulation grows by about 2,000 metric tons a year. If all of the current nuclear power stations get 20-year license extensions—and every plant that applied so far has been approved—then the stock of spent fuel will exceed the capacity of Yucca Mountain.

“The total you are looking at is 135,000 to 140,000 metric tons,” she said. “That’s if we don’t build any new reactors. So we are looking at more (nuclear waste) than the DOE thinks Yucca Mountain will hold.”

There are geologic constraints on expanding the underground storage capacity of Yucca Mountain, said Macfarlane. She said the mountain is laced with faults and fractures which can provide a pathway for water from the surface to reach the repository level.

The seminar was organized by the AAAS Center for Science, Technology and Security Policy, which seeks to advance the integration of science and public policy for national and international security. The center regularly sponsors seminars and briefings for policymakers on critical scientific and technical issues related to national security.

In the 2006 State of the Union Address, President George W. Bush announced a new initiative called the Global Nuclear Energy Partnership (GNEP), designed to increase the use of nuclear power both in the United States and abroad. The plan called for the U.S. and other nuclear-advanced nations to provide nuclear fuel for power plants in developing nations. The plan also called for the advanced nations to take back the spent nuclear fuel from the developing nations, thus relieving those countries of the burden of the nuclear fuel cycle.

One of the details that must be worked out before implementing such a plan is spent fuel management. GNEP includes an ambitious plan to reprocess, or recycle, spent fuel to remove the very radioactive elements from the uranium and plutonium nuclear fuel. This allows the uranium and plutonium to be reused, and, in theory, reduces the need for waste storage. The Center’s briefing examined what the change in waste volume, mass, and heat output would really be, and how much such a venture might cost over the 150 year lifetime of such a project.

Nuclear energy expert Clifford Singer, a professor of nuclear, plasma and radiological engineering at the University of Illinois Urbana-Champaign, said GNEP has many technical problems and uncertainties.

For instance, he said at the seminar, how can the U.S. fulfill its bargain with developing countries to store spent nuclear fuel?

“There is no way we can take anybody else’s spent fuel until we have a well worked-out program for dealing with our own spent nuclear fuel,” said Singer. “We have right now in our own backyard a non-functional system so there is no hope getting GNEP to work, the global part, until this is sorted out.”

Currently, Yucca Mountain is the only designated site for long-term spent fuel storage. Tentative plans call for putting exhausted fuel rods into casks and then putting these under Yucca Mountain where they are to be cooled by air for 300 years. Then the repository is to be sealed.

Obviously, said Singer, “there is less storage allowed than needed.”

Heat, not volume, is a major constraint on Yucca Mountain. As the radioactive fuel decays, it gives off huge amounts of thermal energy. This heat load in the mountain must be carefully regulated for the repository to be safe.

One way to control the heat in Yucca Mountain is to store the sealed casks of spent fuel at or near the surface for 100 years. This could lead to two possibilities: that the heat diminished enough to store all the casks in Yucca Mountain, or if the heat load decreases and some reprocessing is possible then the material would be easier to store.

Another suggestion, said Singer, is that the nation follow a French plan that calls for one round of reprocessing to make a mixed plutonium-uranium oxide fuel that could be used in the current light water reactors. Still a third possibility, he said, is to develop heavy metal reactors that would burn plutonium and americium, the material that contributes the highest thermal load to the spent fuel.

“It is americium decay that dominates the spent fuel destiny,” said Singer. “Americium is the primary component for the few hundred years of the heat load and determines how closely you can pack the (spent) fuel (in the repository). It is not the volume of the waste, it is the amount of americium.”

By burning americium in liquid metal reactors, there would be less heat generated from the spent fuel stored in Yucca Mountain, he said.

Singer noted, however, that “coupling GNEP to burning of plutonium and americium has many technical problems and uncertainties.”

Although building such liquid metal reactors is physically possible, said Singer, the problem is the cost, about $4 billion a year starting in 2020.

“When you take the cumulative additional cost of taking this approach over time,” he said, “it adds up to what anyone would say is a large amount of money—in the trillions of dollars.”

Still, Singer said he was not critical of the GNEP idea.

“The global goals of GNEP itself, as enunciated by the U.S. Secretary of Energy, are sound and can be accomplished in other ways for which the technology is already available,” he said.

Paul Recer

2 May 2006