Scientific American examines spent nuclear fuel

 Spent Nuclear Fuel: A Trash Heap Deadly for 250,000 Years, or a Renewable Energy Source? 

Scientific American

January 28, 2009

I.                Nuclear waste is either a millennia's worth of lethal garbage or the fuel of future nuclear reactors--or both

By David Biello

 [This is Part 3 of an In-Depth Report on The Future of Nuclear Power.]

A 98-foot-wide, two-mile-long ditch with steep walls 33 feet deep that bristles with magnets and radar reflectors will stand for millennia as a warning to future humans not to trifle with what is hidden inside the Waste Isolation Pilot Project (WIPP) outside Carlsbad, N.M. Paired with 48 stone or concrete 105-ton markers, etched with warnings in seven languages ranging from English to Navajo as well as human faces contorted into expressions of horror, the massive installation is meant to stand for at least 10,000 years—twice as long as the Egyptian pyramids have survived.

But the plutonium ensconced in the salt mine at the center of this installation will be lethal to humans for at least 25 times that long—even once the salt walls ooze inward to entomb the legacy of American atomic weapons. And WIPP will only hold a fraction, though a more deadly fraction, of the amount of nuclear waste the U.S. plans to store at Yucca Mountain in Nevada or some other site designated to replace it as a permanent repository for the residue of nuclear reactions.

The Desert Space Foundation, an arts group in Las Vegas, Nev., sponsored a contest to come up with a similar warning system for that site. The winner: genetically-modified yucca cacti turned cobalt blue that would be planted across the entire Yucca Mountain site—to serve as a warning to future civilizations of the radioactive waste within the mountain fastness.

But eerie blue cacti or massive monoliths in the desert may attract rather than repel future explorers—the warnings of the Egyptians did little to deter modern archaeologists. There already are those who see what would be hidden inside Yucca as a resource rather than a curse—after all, as much as 95 percent of the energy in fissile uranium remains in the waste. "The majority of the energy is still in the spent fuel," says Rod McCullum, director of the Yucca Mountain project at the Nuclear Energy Institute (NEI), an industry group. "With Yucca Mountain, you can pull [the nuclear waste] out and reprocess it."

Lonely mountain

In 1987 Congress passed legislation that required the Department of Energy (DoE) to take possession of and properly store thespent fuel from the nation's 104 nuclear reactors by the then far-off date of February 1998. Now 11 years behind schedule, the DoE's primary response—to bury it deep within Yucca Mountain—is no closer to being a permanent solution.

The Energy Department last June finally applied to the U.S. Nuclear Regulatory Commission (NRC), the federal government agency that oversees the nation's nuclear power plants, for a license to build the repository at Yucca. But taxpayers still spend roughly $1 billion a year in fines paid by the federal government) to utilities to compensate them for the delay.

All told, the nuclear reactors in the U.S. produce more than 2,000 metric tons of radioactive waste a year, according to the DoE—and most of it ends up sitting on-site because there is nowhere else to put it. "When we remove fuel from the core after its final usage, we store it in a pool on site. We have the capacity to store it there for many years," says Bryan Dolan, vice president of nuclear development at Duke Energy Corp., which operates three nuclear power plants in South Carolina. The amount of space required to store it, after all, is "incredibly small."

In fact, the U.S. nuclear industry has produced roughly 64,000 metric tons (one metric ton equals 1.1 U.S. tons) of radioactive used fuel rods in total or, in the words of NEI, enough "to cover a football field about seven yards deep." (Of course, actually concentrating rods this way would set off a nuclear chain reaction.)

The 1987 measure designated Yucca Mountain—a range of volcanic rock 90 miles (160 kilometers) northwest of Las Vegas in a patch of desert near former nuclear weapon testing sites—as the nation's permanent repository for all of its used fuel. Critics, including environmentalists and Nevada residents and politicians, charge the site is unsuitable for a variety of reasons, most notably because of its proximity to fault lines (earthquakes have already damaged some buildings at Yucca Mountain) and because water that flows through its rock may ultimately circulate radioactive waste into the soil or drinking water.

But the federal government has already spent some $11 billion building a kind of reverse mine, a deep shaft bored into the side of the mountain sheathed in stainless steel in which to bury the waste. To complete the repository would require at least $90 billion in total, according to a Bush administration estimate in 2008, and would not come online before 2017 at the earliest.

That far-off goal seems increasingly unlikely. The powerful Nevada Democrat, Senate Majority Leader Harry Reid, is a leading opponent of storing nuclear waste in his home state. Pres. Barack Obama appears to agree. In 2007 Obama, then a junior senator from Illinois, wrote in a letter to Reid and Sen. Barbara Boxer (D–Calif.) noting that "the selection of Yucca Mountain has failed, the time for debate on this site is over, and it is time to start exploring new alternatives for safe, long-term solutions based on sound science."

And on January 5, Reid said in a statement that Obama "reiterated his promise to work with me to prevent the dump from ever being built."

Finding an alternative or figuring out how to make Yucca Mountain work—there is already so much nuclear waste in the U.S. that, according to NRC, if Yucca were already open, by 2010 it would be filled to its statutory limit of 70,000 metric tons—will take up "a significant part of my time and energy," new Secretary of Energy Stephen Chu, a physicist, testified during his Senate confirmation hearing earlier this month. "We do need a plan on how to dispose of that waste safely, over a long period of time."

Back in 1983 the DoE selected eight possible candidates for permanent storage other than Yucca, including the Vacherie salt dome in Louisiana; the Richton and Cypress Creek salt domes in Mississippi; salt beds in Deaf Smith and Swisher counties, both in Texas; as well as Davis and Lavender canyons in Utah; and the volcanic basalt beneath Hanford, Wash. Other suggested alternatives have included burying the radioactive waste at sea or shooting it into space.

But the federal government has spent more than two decades developing Yucca, leaving it the readiest candidate for a permanent repository. In its absence, the DoE continues to pay fines to the various nuclear power plantsaround the country for not providing storage for their waste—and the spent nuclear fuel piles up.

Spent fuel

At present, the nation's nuclear facilities store spent fuel on-site in pools or dry casks. "Our agency is on record as being confident that fuel can be stored safely on-site at reactors in either pools or dry casks for at least 90 years," says David McIntyre, an NRC spokesman.

The glowing nuclear fuel rods rest beneath 40 feet (12 meters) of pale blue water (laced with boron to block stray neutrons, the uncharged atomic particles that initiate a nuclear reaction) and slowly decay for a decade or more. New reactors will be built with at least 18 years worth of spent fuel storage capacity, according to Ed Cummins, vice president of regulatory affairs and standardization at nuclear reactor–maker Westinghouse Electric Co. "The earliest plants are expected in 2015, so you're at 2033" before any additional steps—such as shipping the spent fuel to a repository—would need to be taken.

But nearly all of the nuclear power plants in the U.S. have already run out of storage space, because these pools were not designed to be long-term containers and enough room needs to be preserved in case of a crisis such as a meltdown. In the absence of a long-term solution (such as burying the waste deep inside Yucca Mountain), the nuclear industry has turned to so-called dry cask storage.

This involves immersing the radioactive used rods in helium or some other inert gas and slotting them into a steel container that is further encased in a concrete cask—at a cost of roughly $1 million per cask. The encased rods still manage to emit roughly one millirem of radiation per hour and heat the outside of the 100-plus ton concrete casing to as much as 90 degrees Fahrenheit (32 degrees Celsius).

"These are placed in rows on a concrete pad for stability. They're essentially out in the air," says NRC's McIntyre. "Generally, they are putting them within the controlled area of the reactor site so they are protected under the physical security of the plant."

Some 9,000 metric tons of spent fuel rods are already stored encased in some 900 such casks—the bulk of them stored vertically in concrete casks but some placed horizontally into concrete bunkers. Their makers—companies like New Jersey-based Holtec International and AREVA's Transnuclear, Inc.—and the NRC maintain that such dry cask storage will last for at least a century, if not longer. "They've had an excellent safety record over the past 22 years they've been in use," McIntyre says. "All signs are that they are safe and secure."

But some environmentalists and other nuclear power critics contend that such dry casks present a tempting target for terrorists and a disaster for the environment if ever breached. In fact, the San Luis Obispo, Calif., chapter of Mothers for Peace has successfully sued the NRC and power utility Pacific Gas & Electric Co.—owners of the Diablo Canyon power plant—for failing to take into account the impact of a potential terrorist strike when assessing the environmental risks of a new, proposed on-site dry cask storage area.

The solution may be one or many interim storage sites, centralized depots where such dry casks could be stored until a permanent repository is opened. Eleven communities in Idaho, Illinois, Kentucky, New Mexico, Ohio, South Carolina, Tennessee and Washington State have expressed an interest in being the host of such a facility, according to NEI. "It should be wherever it can be sited and it should be at a voluntary location," NEI's McCullum says. "Anything that is on the way to Yucca Mountain from most of the reactors," which are in the eastern half of the U.S.

Recycling

In 1972 General Electric Co. closed a building in Morris, Ill., that would have presented another alternative solution to the problem of nuclear waste: reprocessing. The U.S. government originally employed this technology—dubbed PUREX (for plutonium and uranium recovery by extraction)—in both Barnwell, S.C., and West Valley, N.Y., to separate out the plutonium and other reusable fission products from nuclear waste. Today, France, Japan, Russia and the U.K. have reprocessing facilities that extract fresh fuel by enriching spent nuclear rods—albeit also producing radioactive waste by-products that have to be dumped.

The problem is that this is also how governments separate out plutonium for use in nuclear weapons—potentially creating a tempting target for theft. "One of the biggest obstacles to increasing security is the proliferation of reprocessing plants, which produce separated plutonium that can be used in weapons," says physicist Edwin Lyman, a senior staff scientist at the Union of Concerned Scientists (UCS), a nonprofit that advocates for a healthy environment and safer world. "We do not think any reprocessing scheme existing or proposed can mitigate the serious concern of proliferation and nuclear terrorism." Some 250 metric tons of plutonium—enough for 30,000 nuclear weapons—has already been reprocessed by the aforementioned countries, according to the group.

The Bush administration revived interest in such reprocessing via the Global Nuclear Energy Partnership (GNEP) in 2006. This DoE program proposes restarting the recycling of nuclear fuel in the U.S. by building a new reprocessing plant, which prompted GE to reopen the Morris, Ill., site, among other companies stepping forward. At the same time, the Energy Department has enlisted 21 nations, from Australia to Kazakhstan, to safely develop such reprocessing technology, in many cases by shipping any future spent fuel to this proposed U.S. facility.

The National Research Council, the research arm of the U.S. National Academy of Sciences, notes, however, that such reprocessing is impractical and expensive. In 1996 it estimated that reprocessing of existing used nuclear fuel could cost more than $100 billion. Eleven years later, the Council further declared that research and development of such technology under the GNEP should be halted, because the money could be better spent on other areas of nuclear power research, such as next-generation reactors.

The nuclear power industry has also not shown much enthusiasm for reprocessing because of the high price tag. "This GNEP program is aimed at trying to understand whether you could reprocess spent fuel economically," says Westinghouse's Cummins. "I would suggest that it is not really economical."

A 2007 report issued by Colorado think tank, The Keystone Center—an analysis of nuclear power by utility executives, environmentalists, policymakers and other experts—agrees, finding that "reprocessing of spent fuel will not be cost-effective in the foreseeable future."

"Commercial spent fuel has plutonium in it and you can think of that as an ore that could be mined for fissile material," Lyman notes. But "the cost of extracting plutonium from that ore is still much, much higher than the price of uranium."

Nevertheless, advocates including researchers at Idaho, Argonne, Los Alamos and Oak Ridge national laboratories point to a reprocessing future of so-called fast-breeder reactors, which use plutonium to generate electricity—and in the process of fissioning generate yet more plutonium, a theoretically inexhaustible source of energy. "In theory, it could produce a self-sustaining energy supply," Lyman acknowledges. "But in practice it's never worked."

In fact, the Monju fast-breeder reactor in Tsuruga on Japan's west coast was shut down in 1995 after slightly more than a year of operation because of political opposition and difficulties running it, including a fire caused by a leak of its liquid sodium coolant, despite a cost of more than $6 billion to build.* "Breeders are difficult reactors, they are complex reactors," Westinghouse's Cummins says. "There have been some built but not many more. They are just not economical at the moment."

And even if reprocessing or fast breeders could be made to work cheaply and efficiently—eliminating spent reactor rods as radioactive refuse—there would still be thousands of tons of nuclear waste in need of a permanent home.

The other nuclear waste

The U.S. produces as much as 160,000 cubic feet (4,530 cubic meters) of radioactive material from its nuclear power plants annually—a number that spikes higher dramatically when old nuclear plants are decommissioned, such as Maine Yankee in Wiscasset, Me., in 1997. Ranging from workers' coveralls to water filters, some of this stream of nuclear waste no longer has a place for its disposal either—particularly the highly radioactive materials rated as classes B and C, such as reactor vessel heads. "That stuff has only one place it can go," says Ralph Andersen, chief health physicist at NEI, "a deep geologic repository," like Yucca Mountain.

The national nuclear dump in Barnwell, S.C., was closed to shipments of such waste from nuclear power plants in 36 states in July 2008. A new dump in Texas, granted a license by the state this month, will only accept low-level leavings from that state and Vermont, alongside similarly restricted dumps in Utah and Washington State. This has also left users of nuclear products such as hospitals and universities scrambling to find a place to dispose of their radioactive residue.

So now the waste from the majority of reactors on the east coast and Midwest typically sits alongside the spent nuclear fuel indry casks on-site. In terms of safety, it's the best that can be done at present.

"Where would I want to store radioactive materials? Somewhere where there were armed security officers with concrete buildings," Andersen says. "What we've got at a nuclear power plant is an armed fortress made out of concrete."

 

*Erratum: (1/29/09): This sentence was changed after publication. It originally stated that the Monju fast-breeder reactor used molten salt coolant. Thanks to bhoglund for pointing out the error.