Another nuclear reactor has been damaged by corrosion.

Leaking coolant caused minor corrosion to a reactor at the Tennessee Valley Authority's Sequoyah nuclear plant near Chattanooga, Tenn., but was never a safety problem, a Nuclear Regulatory Commission spokesman said.

More severe damage caused by boric acid corrosion was reported last March at Davis-Besse, the nuclear plant in Perry that is owned by Akron-based FirstEnergy Corp.

The damage at the Sequoyah plant's Unit 2 reactor was discovered after an unrelated shutdown on Dec. 26, according to the NRC.

``It is just some residue with slight corrosion, but they did find it and they didn't find any evidence of serious problems elsewhere,'' said Ken Clark, an Atlanta region spokesman for the NRC.

TVA spokesman John Moulton said the corrosion caused a ``slight indentation on the reactor vessel head that did not require repair.''

``NRC was notified, but there was no threat to the health and safety of employees and the public,'' Moulton said Tuesday. He said the leak was repaired and the reactor was returned to service.

Last year, workers at the Davis-Besse plant found a pineapple-sized hole etched through a reactor's 6-inch-thick steel lid. Only a thin liner prevented radioactive coolant from spilling out.