Mar. 17--As Duke Power considers building a new nuclear plant in Cherokee County, S.C., a move it announced Thursday, federal officials are still wrestling with what to do with the nation's tons of radioactive used fuel.

Spent fuel, as it is called, is typically stored at the power plants where it was used. Construction of a permanent disposal site in the Nevada desert still hasn't won final approval.

Critics charge that on-site cooling pools, where hot fuel fresh from the reactor goes for five to seven years, are potentially dangerous.

The National Academy of Sciences, in a report last year, said successful terrorist attacks on spent fuel pools would be difficult but possible.

An attack leading to a fire, it said, could release large amounts of radioactive material if the metal-clad fuel rods burn.

The nuclear industry, including Duke, say the plants are among the most secure facilities in the world.

In addition to the pools, Duke stores spent fuel in sealed metal cylinders called casks that are then enclosed by metal or concrete outer shells. The Nuclear Regulatory Commission sanctions that storage method.

Duke uses cask storage at its McGuire plant on Lake Norman and Oconee plant near Seneca, S.C. It's planned to begin at the Catawba plant on Lake Wylie this year or next year, Duke has said.

Duke won't say how much spent fuel is stored at its plants, information the federal government now considers security- sensitive. The Congressional Research Service reported that, in 2002, Oconee stored 1,615 tons, McGuire 1,178 tons and Catawba 861 tons.

"Used fuel storage at any new plant is something we have to factor into the project," said Duke spokesman Rita Sipe.

The used fuel is safe where it is, says the Nuclear Energy Institute, an industry group, but the plants weren't intended for long-term storage. "The onus is on the government to meet its obligation" for a permanent disposal site, spokesman Steve Kerekes said.

The Department of Energy has no estimate of when it will open the repository at Nevada's Yucca Mountain, The New York Times reported last month.

"We have confidence that the federal government will continue moving the project forward," Sipe said.

While Yucca Mountain is limited to 70,000 metric tons of waste -- nearly as much as is now stored at power plants -- the site is big enough to hold more, federal studies say. The Department of Energy recently proposed recycling spent fuel, reducing the amount that has to be disposed.

Arjun Makhijani, president of the Institute for Energy and Environmental Research, an industry critic, said power plants have a generally good safety record of storing their own spent fuel.

But he says as much fuel as possible should be moved out of pools. Makhijani also says storage casks should be fortified by hardened sleeves to withstand an attack.