Federal regulators are partially opening the door for a Minnesota Indian tribe to challenge Xcel Energy's request for a 40-year extension on its license to store highly radioactive waste in casks on the site of the Prairie Island nuclear power plant near Red Wing, Minn.

But the staff of the Nuclear Regulatory Commission in a filing this week said the Prairie Island Indian Community, many of whose members live next to the plant, shouldn't be allowed to raise one of its main issues -- that the environmental questions about longer-term storage have been inadequately studied.

The NRC staff says the tribe should be able to raise other safety issues regarding radioactive waste in the pending licensing case. But Xcel Energy Inc., the plant's owner, in a separate filing, argued that none of the tribe's safety-related contentions should be considered.

The relicensing question, largely procedural at this stage, is before the U.S. Atomic Safety and Licensing Board, a body within the NRC.

Xcel's 20-year license to store radioactive waste on site in casks expires in October 2013. When that license was issued, it was expected that the federal government would establish a permanent radioactive waste site where the waste eventually would be shipped. But no permanent storage facility has been built, and the plan for one in Yucca Mountain, Nev., has been dropped.

In June, the U.S. Circuit Court of Appeals for the District of Columbia struck down NRC's waste-storage policy, saying 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."

That ruling has emboldened the Prairie Island tribe to petition for an expanded study of the risks of storing spent fuel rods in casks for decades longer than intended. Yet the NRC staff said the commission wants to avoid such plant-by-plant reviews until regulators can consider the waste-storage issue more broadly.

Xcel has taken a similar position in its filing but went further, arguing that none of the tribe's contentions should be heard by the board. On Friday, the utility said it still welcomes the tribe's participation in the license-extension case but disagrees with its contentions and believes there are other procedural ways for tribal officials to make its point.

"As we said before, 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.

The tribe can respond before the board decides how much of the tribe's argument it will hear. The tribe had no comment Friday.

The Prairie Island plant, with its two reactors, has 29 casks storing spent fuel and will need at least 35 more because it's expected to operate for 22 more years. About 200 tribal members live near the plant.

David Shaffer • 612-673-7090