As workers began inspecting a leaky tube in one of the San Onofre nuclear plant's reactors Thursday, federal regulators said more than 800 tubes in a second, offline reactor showed wear and thinning, although they are only two years old.

And plant officials confirmed that sensors showed a tiny amount of radioactive gas may have leaked out of a building next to the first reactor before the reactor was shut down late Tuesday.
Article Tab: image1-San Onofre: 100s of troubled tubes, gas leak

All four of the plant's steam generators and their tubes are about two years old, installed after being delivered to the West Coast by the Japanese manufacturer of the generators, Mitsubishi Heavy Industries.

Some 9,700 tubes carry water from the reactor and through each generator.

"They have inspected 80 percent of the tubes in one of the steam generators at unit 2," said Victor Dricks, spokesman for the Nuclear Regulatory Commission. "Two of the tubes have thinning so extensive that they need to be plugged and taken out of service. Sixty nine other tubes have thinning greater than 20 percent of the wall thickness, and a larger number have thinning greater than 10 percent of wall thickness."

The tubes with 10 percent thinning number more than 800, he said.