PIKETON, Ohio – Federal officials are scratching their heads over 46,000 rusting steel cylinders containing depleted uranium that are stored here and at two other large nuclear installations.

The cylinders, containing more than 1.1 billion pounds of uranium hexafluoride used to make atomic fuel, have been accumulating for nearly half a century at the Portsmouth Gaseous Diffusion Plant in Pike County, the Oak Ridge National Laboratory in Tennessee and the Paducah Gaseous Diffusion Plant in Kentucky.

A few of the 14-ton cylinders have begun to leak. And, although federal officials say there has been no environmental contamination, experts say that is no reason to dawdle over taking steps to keep one more federal nuclear environmental problem from developing. The government is taking steps to improve storage conditions and reinforce cylinders that are badly rusted. But for decades, not much attention was paid to them. The cylinders were stacked so close together that they could not be inspected for leaks.

The situation has attracted state environmental officials.

”We are concerned with the way they are being managed,” said Donna Goodman, of the Ohio Environmental Protection Agency. However, Goodman refused to comment specifically on the cylinders, citing delicate negotiations between state and federal officials. The state wants to gain some control over the cylinders at Piketon. It already has general oversight of the $ 8 billion environmental cleanup at the plant.

Eugene Gillespie, U.S. Department of Energy supervisor at Piketon, said the 13,800 cylinders at the Piketon plant do not pose an environmental or health threat. Radiation from material leaked onto the ground cannot be detected farther than a few feet away from the leak, he said.

Since 1992, when two leaking cylinders were discovered, the cylinders most subject to corrosion have been examined annually.

Energy Department officials feel they have another 25 years before they have to begin converting the older material, a process that could take 30 years and could cost up to $ 10 billion, according to Gene Hoffman, a retired metallurgist who worked at Oak Ridge.

But, Hoffman said, the Energy Department should not feel it has time on its hands. He agreed there is no immediate danger. But, he believes there is a danger of significant deterioration of the cylinders before the government has a plan to use or convert the uranium.

”What if you parked a car in your back yard for 50 years? You’d sweep it up with a broom,” he told a public hearing at Piketon recently.

The depleted uranium in the cylinders is the remains of material used to enrich nuclear fuel used in atomic reactors. While Hoffman describes himself as being ”pro-nuclear,” he said the government approached the uranium waste as it has other nuclear-related problems and put the stuff aside with no idea what to do with it.

”The longer the cylinders sit there, the worse the problem becomes,” said Woody Cunningham, technical director for the Defense Nuclear Facilities Safety Board.

When a cylinder is rusted through, the material reacts with air to form compounds of uranium and fluorine. Some of these compounds are solid and plug the leak. However, the metal continues to corrode.

Both radiation and hydrogen fluoride, a deadly gas even when diluted by air, can escape.

The largest breach discovered so far has been at Piketon when an estimated 110 pounds of UF6 was lost over about 13 years, Gillespie said.

A 1992 Energy Department report noted that while the releases of material have been very small, that leaks could result in mild radioactive contamination of the storage yards and adjacent cylinders and could result in low levels of contamination to people working in the area.

Soil samples around the yards do not show any contamination.

Cunningham said the Energy Department has begun to adopt board recommendations that the cylinders should be moved to better locations for storage and they should be inspected and painted to retard corrosion.

But these are only short-term measures, he said. The long-term solution is to transform the uranium fluoride into a stable form of uranium or to use it in some manufacturing process.

A small amount has been used in military applications. Uranium is a heavy metal and it has been used to make armor-piercing artillery and tank gun shells and as a component in stronger tank armor.

But these applications require small amounts of what is in storage and the ultimate solution is to transform the uranium fluoride into a more stable, less dangerous form.

Cunningham agrees there is no short-term environmental danger from leaking radiation. The risk from hydrogen fluoride is greater, but the cylinders are not yet human health or environmental problems, he said.

This gives the Energy Department time, something it doesn’t have in difficulties it faces at other sites. But, Cunningham said, it’s time that should not be wasted.

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