The long debate over storing radioactive waste next to the Prairie Island nuclear power plant is boiling up again with an old question: Is the waste ever going away?

The 882-member Indian tribe whose southeastern Minnesota land adjoins the Prairie Island nuclear power plant is petitioning the federal government for a deeper look at the risks of on-site storage because outdoor casks holding spent fuel rods likely will remain in place for decades longer than ever intended.

"They've said it was temporary," said Ron Johnson, secretary of the Prairie Island Indian Community. "This fuel was supposed to have been removed in the 1990s. We translate that to mean it's probably more of a permanent storage facility."

The federal government has failed for decades to establish a permanent radioactive waste site, forcing the nuclear industry to recognize the reality of long-term, on-site storage.

In June, a federal appeals court acknowledged the problem, striking down new waste-storage rules and ordering regulators to do a more thorough analysis of storing radioactive waste at reactor sites for up to 60 years after a plant shuts down. Since the ruling, citizen and environmental groups have challenged on-site waste storage at 15 other U.S. nuclear power plants before the Nuclear Regulatory Commission's Atomic Safety and Licensing Board.

Now the tribe, some of whose members live within 600 yards of the Prairie Island plant, is raising the issue as the NRC considers a request by Xcel Energy, the plant's owner, to extend the license of its dry cask storage for 40 years. Its current waste-storage license expires in October 2013.

Xcel, a Minneapolis-based utility that serves 1.1 million customers in Minnesota, said it welcomes the tribe's participation in the re-licensing process.

The tribe has hired John Greeves, retired director of NRC's waste management and environmental protection division, as an expert consultant. Greeves said sealed casks used to store spent, highly radioactive fuel rods have leaked at two U.S. plants, in 2000 and 2011, in one case because of corrosion.

"Based on the history of [cask] defects that have caused leaks to occur ... it can reasonably be anticipated that over a 60-year license period, one or more ... casks will experience confinement failure, which can lead to [an] off-site dose to members of the public," Greeves said in an affidavit.

The Prairie Island plant now has 29 such casks and plans to add more because the plant is expected to operate another 22 years. In regulatory filings, Xcel has described 60-year, 100-year, and 200-year storage scenarios.

Eventually the waste is supposed to go to a permanent repository. But the prime candidate, Yucca Mountain in Nevada, has been dropped by the Obama administration, with no other option in sight. The nuclear industry's current hope is that an interim repository can be developed.

Xcel didn't respond directly to the tribe's safety contentions, but said it will formally reply to the NRC.

"We greatly value our relationship with the Prairie Island Indian Community, and we have many common interests and concerns, particularly the interest in holding the federal government accountable for removing used nuclear fuel from the plant site," the company said in a statement.

Johnson, the tribal secretary, said the government not only should set a clear deadline to remove the waste, but should offer better protections in the meantime. About 200 tribe members live on or near the reservation, which is also the site of the Treasure Island Resort and Casino, which draws more than 8,000 visitors on some days.

The license review marks the latest chapter in a long confrontation over nuclear waste at Prairie Island. The issue landed in the Minnesota Legislature in 1991 and 2003, where lawmakers approved compromise measures temporarily allowing the waste to stay.

But the safety questions were revived in the case brought by four northeastern states, the tribe and other groups. The U.S. Circuit Court of Appeals for the District of Columbia ruled that the lack of a national nuclear waste repository means that spent nuclear fuel "will seemingly be stored on site at nuclear plants on a permanent basis" and the NRC needs to address that reality.

The tribe, in its Aug. 24 petition about Prairie Island, said that because of "misplaced reliance on an imminent permanent storage solution," the NRC hasn't adequately considered the risks if casks are used for many decades.

Of particular concern, the tribe contends, are newer "high burn" fuel rods that become even more radioactive as waste. Spent fuel rods taken from reactors cores are routinely cooled for several years in an indoor pool, then put into casks stored outside the reactor building.

Geoffrey Fettus, an attorney for the Natural Resources Defense Council, which was part of the earlier storage-safety litigation, said he expects the NRC will conduct a broad environmental study of the long-term radioactive waste storage, including pools that hold spent fuel at reactors, and then turn to site-specific concerns like Prairie Island's.

Whether the tribe gets to make its case immediately is uncertain. The NRC has a complex process for intervenors that can go on for years.

Tribal General Counsel Philip Mahowald said the federal government bears the blame for the nation's failure to develop a permanent nuclear waste disposal facility.

"They have willfully failed to take action," Mahowald said. "Everybody pats us on the head and says, 'Don't worry, it will be safe.' If it is so small of a risk, why not move it out? Why do you have to keep it here?"

David Shaffer • 612-673-7090