By Malia Rulon
The Associated Press

WASHINGTON - Davis-Besse nuclear plant's plan to fix a flaw in emergency cooling pumps by installing a metal debris strainer is not guaranteed approval, federal regulators said Tuesday.

The Nuclear Regulatory Commission must sign off on the repairs before the plant near Toledo can restart.

Plant engineers discovered in March that small particles could pass through the pumps' filters and damage the pumps' bearings, causing them to fail. The emergency pumps keep the hot, radioactive reactor core supplied with coolant in case of a rupture. There is no backup.

Bob Coward, an engineer with plant owner FirstEnergy Corp., told NRC officials Tuesday that the strainer was tested over several days using particles of different sizes and density.

"We actually skewed our debris particles smaller to allow them to get through the pump strainer," he said, adding that the pump was able to withstand the tests.

If the plant goes ahead with the fix, it is doing so at the risk that NRC officials won't approve the finished pumps, regulators said.

"You've answered a number of questions from the NRC staff, but you should not infer that we have found this pump to be acceptable at this stage," said Bill Ruland, NRC project director for nuclear power plants in the Midwest.

The plant along Lake Erie near Toledo has been shut down since February 2002. A month later a leak was discovered that had allowed boric acid to eat nearly through the 6-inch-thick steel cap covering the plant's reactor vessel. Akron-based FirstEnergy hopes to restart the plant this fall.

The modification plan likely will pass muster, said David Lochbaum, a nuclear safety engineer and industry watchdog for the Union of Concerned Scientists.

"I feel good that the tests are already completed," he said. "Anything can look good on paper, but they have already run this design for 21 days."

The pump modification is expected to cost $7 million, FirstEnergy spokesman Todd Schneider said. Replacing the pumps would cost much more because Davis-Besse is the only plant in the nation whose emergency high-pressure pumps are designed this way.

Meanwhile, a report released Tuesday by the NRC's inspector general said government inspectors at the plant failed to pass along reports of numerous instances of boric-acid leaks and corrosion to agency headquarters.

That caused the agency to miss warning signs of the corrosion, which the agency said was the most extensive ever found on top of a U.S. nuclear plant reactor.

The inspector general prepared the report after Ohio Rep. Dennis Kucinich asked for a closer look at NRC oversight of the Davis-Besse plant. Kucinich, running for the Democratic presidential nomination, said the report "demonstrates a complete failure at every rung of NRC's bureaucratic ladder."

NRC spokeswoman Sue Gagner said the agency was studying the findings.