The nation’s nuclear waste is piling up. The proposed storage site at Nevada’s Yucca Mountain has been nixed — possibly for good. And the problem is only growing more acute: On Friday, a D.C. federal appeals court ruled that the current strategy of keeping waste on-site at power plants around the country may not be viable. So what can the United States do instead?

A truck takes a shipment of transuranic waste from Los Alamos National Laboratory to the Waste Isolation Pilot Project in Carlsbad, N.M. (Patricia Leyba/ Los Alamos National Laboratory )

At least, that was the suggestion from Allison MacFarlane, President Obama’s nominee to head up the Nuclear Regulatory Commission. At her confirmation hearing on Wednesday, MacFarlane was grilled by senators about her views on how best to dispose of the nation’s spent nuclear fuel. As a possible model for future repositories, she pointed to the Waste Isolation Pilot Plant in Carlsbad, N.M., which opened in 1999 and now handles the radioactive leftovers from U.S. defense facilities.

Any long-term storage facility for nuclear waste will have to overcome local unease and opposition — that’s what’s bogged down Yucca Mountain. But Carlsbad’s $2.5-billion plant was actually welcomed by local residents, who were worried about what would happen to the area’s economy once its potash mines ran out. As Roger Nelson of the Energy Department’s Carlsbad office told me, Carlsbad’s residents managed to lobby wary state legislators in New Mexico to drop their opposition. Since the plant opened a decade ago, the small desert town of 27,000 has been teeming with high-tech jobs.

Recently, a 15-member blue-ribbon commission set up by Obama to find alternatives to Yucca urged a similar “consent-based” approach in locating a waste repository. As MacFarlane, a geologist who served on the commission, explained at her Senate hearing, that process would involve finding communities who were amenable to hosting either an interim or permanent nuclear-waste facility and offering some sort of compensation for their troubles. (As part of the WIPP deal, New Mexico received $300 million over 15 years from Congress, mostly for roads.)

“I don’t think we even need to look to other countries for lessons [on how to handle nuclear waste],” MacFarlane said. “We’re the only country with a deep geological repository already up and running — and it’s in New Mexico.”

Of course, Carlsbad’s WIPP plant isn’t a perfect model. That site mostly handles barrels of tools, equipment, and clothing contaminated by plutonium, radioactive rubbish trucked in from defense facilities like Los Alamos National Laboratory near Santa Fe or the Rocky Flats Plant near Denver. By contrast, a long-term waste facility of the kind that was planned for Yucca would need to deal with spent nuclear fuel rods that are more radioactive and need to be buried in unbreakable containers deep inside a geological repository for centuries. That’s a more daunting task.

Still, the waste issue is growing more urgent. At the moment, the nation’s nuclear reactors are storing about 70,000 tons of used fuel on-site. The spent fuel rods cool for years in giant swimming pools full of water and are then transferred to dry casks of fuel and concrete. Many of those pools are now reaching their limit, and the amount of waste is expected to double in the next 40 years. (MacFarlane has argued that more waste should be moved out of the pools and into dry casks.)

The Nuclear Regulatory Commission has argued that the waste can be safely stored on-site for the next century or so. But last Friday, a D.C. federal appeals court ruled (pdf) that the NRC needs to recheck its work. It’s not clear that a permanent long-term repository will get constructed anytime soon — especially now that Yucca is on hold. So, according to the court, the NRC needs to conduct a review to see if it’s truly safe to keep the fuel on-site at power plants indefinitely.

That puts more pressure on Congress and federal regulators to find a longer-term solution. “We absolutely need to move forward on a repository,” MacFarlane said. “Those dry casks might be fine on a decades-long time scale. But if we’re looking at hundreds or thousands of years, then you need a deep geological repository.”