October 14, 2002 at 1:39 PM EST - Updated June 29 at 7:50 PM
OAK HARBOR, Ohio (AP) - As repairs were under way on a damaged reactor head at the Davis-Besse nuclear power plant, a contractor found acid stains on the reactor's bottom when it was inspected for the first time, FirstEnergy Corp. said.
The Akron-based utility is testing the stains to ensure that tubes through the bottom of the reactor vessel weren't leaking, which would mean more repairs before the plant could reopen next year.
Such leaks are "highly unlikely," company spokesman Todd Schneider said Saturday.
"We believe these stains we saw at the bottom of the reactor are related to washing the reactor head over the last several years," Schneider said. "This is the first time we've looked at the bottom of the reactor because the bottom has been covered in insulation."
The nearly transparent, whitish streaks containing boric acid along the sides and bottom of the reactor vessel were discovered in June.
The streaks could have been an early clue that acid was pooling on the head, Schneider said. Workers originally thought the acid was coming from equipment above the head.
Davis-Besse shut down for routine maintenance in February. But investigators in March found that leaking boric acid had nearly eaten through the 6-inch steel cap on the reactor vessel. The plant about 20 miles east of Toledo has been closed since then.
A new cap has been installed. But last week, FirstEnergy pushed back the projected reopening of the plant to early 2003 instead of the end of this year.
A Nuclear Regulatory Commission spokesman said it was too early to tell if the stains indicate a problem on the reactor bottom.
"There is no evidence at this point to show that they have leakage," spokesman Jan Strasma said. "I would not say the situation is serious at this point."
The NRC has criticized FirstEnergy, saying the leak on the reactor's head could have been detected up to four years earlier. But in an internal review last week, the agency also said it had failed to perform inspections that could have detected the leak.
The utility must give the agency a written report next week on the stains on the reactor bottom.
The bottom tubes, called nozzles, are made of the same nickel alloy as those in the head that leaked. But the nozzles in the head are subjected to 600-degree heat, Schneider said, unlike the smaller tubes on the bottom.
"The temperature is much cooler, making these nozzles less susceptible to cracking," he said.
(Copyright 2002 by The Associated Press. All Rights Reserved.)