CARLSBAD, N.M. — Half a mile beneath the desert surface, in thick salt beds left behind by seas that dried up hundreds of millions of years ago, the Department of Energy is carving out rooms as long as football fields and cramming them floor to ceiling with barrels and boxes of nuclear waste.
The salt beds, which have the consistency of crumbly rock so far down in the earth, are what the federal government sees as a natural sealant for the radioactive material left over from making nuclear weapons.
The process is deceptively simple: Plutonium waste from Los Alamos National Laboratory and a variety of defense projects is packed into holes bored into the walls of rooms carved from salt. At a rate of 6 inches a year, the salt closes in on the waste and encapsulates it for what engineers say will be millions of years.
“It’s eternity,” said Dirk Roberson, a guide for frequent tours the Energy Department gives to visitors to the mine, who leave with a souvenir plastic bag filled with chunks of salt pressed into rocklike form.
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The complications of the present intruded recently, however, when a truck hauling salt in the mine caught fire. Smoke forced an evacuation of workers and a shutdown of waste-burial operations, which officials said was temporary. They said the fire did not affect the radioactive waste, which is stored at the other end of the mine.
Despite the setback, the Waste Isolation Pilot Plant (WIPP) is drawing new attention. With the effort to find a place for highly radioactive waste at a near-standstill, officials say the site might be a solution. It is of particular interest since the demise of the plan for Yucca Mountain — a volcanic ridge 100 miles from Las Vegas chosen by Congress for the storage of nuclear waste from power reactors and weapons, but adamantly opposed by Nevada.
The law limits material buried at the New Mexico plant, which began accepting waste in 1999, to plutonium waste from making weapons, which is exceptionally long-lived but not highly radioactive. The waste from spent nuclear fuel, which is far more radioactive in its first few centuries, is not permitted. But experts say testing and analysis might show that the salt beds at WIPP are a good home for the waste once meant for Yucca.
Some people despair of finding a high-level nuclear “repository” — they shy away from the word “dump” — but Allison M. Macfarlane, a geologist who is chairwoman of the Nuclear Regulatory Commission and who served on a presidential study commission established after the Yucca plan was canceled, said WIPP proves it can be done.
“The main lesson from WIPP is that we have already developed a geologic repository for nuclear waste in this country, so we can in the future,” she said. The key, she said, is a site acceptable to both scientists and the local community.
The salt at WIPP is not much different from what goes into food. Phillip R. Sharp, who also served on the study commission, said that when the group visited Carlsbad, about 25 miles west of the site, commission members were served cocktails — margaritas garnished with salt from the repository.
But the salt behaves strangely around nuclear waste, which is warm to the touch. When the waste is buried in salt, tiny bits of water inside the salt start to move toward the heat. As a result, the salt left behind is stronger, like a good sealant. But it is still basically salt.
“The salt is completely unaffected by any nuclear waste you could imagine, period,” said James Conca, a geologist and former director of the Carlsbad Environmental Monitoring and Research Center, a division of New Mexico State University.
With most things nuclear, however, the politics can be trickier than the science. In the case of WIPP, there is local support but skepticism farther afield.
In the nearby community, business and political leaders are agitating for expansion. John A. Heaton, a Democratic former state representative and the head of the Nuclear Opportunities Task Force, a local business group, argued that the geology was suitable. “The Permian basin is 250 million years old,” he said. “It’s been here a long, long time.”
His group has bought a patch of desert and is now exploring whether the land could be used for interim storage of highly radioactive waste.
Burial here, perhaps after recycling usable components, would be a boon for the area, Heaton added. “Nobody comes in and helps rural areas,” he said. “You have to live by your wits.”
State Rep. Cathrynn N. Brown, a Republican, is also in favor of burying nuclear waste here. “We have a low earthquake incidence, a dry climate and land that’s really not being used for much else,” she said.
But at the state level, there is active opposition. Don Hancock, the nuclear-safety director at the Southwest Research and Information Center, said he has been opposing WIPP since the 1970s, long before construction began. He said that the area was rich in oil and gas and that if someone drilled a well centuries from now, ignorant of what lay below, or if the repository expanded into drilled areas, the waste might escape. The 16-square-mile site is in a region thick with pump jacks, which have multiplied with the fracking boom.
The site should stick to its original mandate of storing plutonium waste, Hancock said. “If WIPP really is a pilot plant, as its name says, we should have WIPP do what it’s supposed to do, and operate safely for 25 or 30 years, and then safely decommission it to demonstrate to us and the world that in fact geologic disposal does work.”
“We should be looking for multiple other places anyway,” he said.
Expanding WIPP would require action by Congress.
Gov. Susana Martinez of New Mexico, a Republican, has taken what amounts to a radical position: undecided. “We haven’t made any decision on any possible future mission for WIPP,” said F. David Martin, the former head of the state’s Environment Department and now the Cabinet secretary-designate for the New Mexico Energy, Minerals and Natural Resources Department. “The governor wants to be assured by the science that it could be done safely.”