An inspection of the damaged Ginna nuclear power plant outside Rochester, N.Y., has revealed that between seven and 10 of the pipes that make up one of the plant's two steam generators are severely damaged. Start-up of the plant may be delayed another three weeks because thousands of other pipes in the generator must be inspected.

A camera inspection showed that two of the tubes inside the steam generator that failed last month were severed, while the other damaged tubes had deep gashes in them. The plant was closed last month when one of the steam generator tubes broke in half, spilling water out of the generator at a rate of 700 gallons a minute and releasing radioactive steam into the air near the plant.

Although the damaged tubes were out of use because they previously showed signs of weakness, they all appeared to have been smashed by a heavy object that may have been loose inside the steam generator.

Nuclear Regulatory Commission Regional Administrator Ronald C. Haynes said that the latest camera inspection showed a piece of boiler plate six inches long, four inches wide and half an inch thick stuck among the damaged tubes.

"We don't know for certain, but it looks as if this metal object may have fallen in there as long ago as 1975, when some changes were made to the top of the steam generator," Haynes said. "Somebody may have cut off a metal strap that fell down in there instead of being removed."

"The pictures are very dramatic," Rochester Gas & Electric Corp. spokesman John Maier said. "It looks like somebody went in there with a hacksaw. Some of the tubes show severe denting and external degradation."

All the damage discovered with thin cable-like, fiber-optic cameras was in tubes that had been plugged and taken out of operation because they previously had shown signs of weakness. Because the tubes were inoperable, RG&E officials thought they couldn't cause trouble.

Haynes said that technicians will have to inspect the entire steam generator, which consists of more than 3,259 tubes, some of which are more than 60 feet long. This process could take as long as three more weeks.