By JOHN SEEWER, Associated Press Writer
TOLEDO, Ohio (AP) - A second hole has been found in a steel cap that covers a nuclear power plant's reactor vessel, the Nuclear Regulatory Commission said Tuesday.
The hole is smaller than one found two weeks ago that federal inspectors said was the most extensive corrosion ever found on top of a U.S. nuclear plant reactor.
"This may provide more information about the cause and how the other cavity developed," said agency spokesman Jan Strasma.
Inspectors at the Davis-Besse nuclear plant two weeks ago found leaking acid caused a 6-inch hole in the steel cap near a cracked control rod nozzle. The second cavity is about 1¾ inches deep, Strasma said.
Investigators said they don't know how long the nozzles have been leaking.
The first hole, which was stopped by a layer impervious to the acid, led the regulatory commission to alert the nation's 102 other commercial nuclear plants to watch for similar problems.
Both holes do not pose a safety threat around the plant, Strasma said.
Even if the acid had penetrated the massive cap and allowed steam to escape, safety systems would have immediately cooled the reactor, he said. And while the steam would contain some radioactive material, it would have been confined by the reactor containment building.
The second hole was found after reviewing robotic and ultrasonic data over the last several days, said Richard Wilkins, a spokesman for Akron-based FirstEnergy Corp., the plant's operator.
"It's pretty preliminary to say what exactly we've got," he said Tuesday. "At this point we don't know until we get the second nozzle out."
The holes were discovered while the nuclear plant, which is along Lake Erie and about 25 miles east of Toledo, was shut down for normal refueling and maintenance.
The damage to the reactor's steel cap will keep the plant shut down until at least May.
Trace amounts of boric acid, a byproduct of the nuclear fission process inside the reactor, are believed to have dribbled onto the cap from at least two of the reactor's 69 control rods.
Plant officials discovered the corrosion during repairs to five control rod nozzles after cracks were found earlier during the shutdown.
FirstEnergy plans to install a new reactor head during the plant's next refueling shutdown in 2004, Wilkins said. The company said a new reactor cannot be installed now because it will take months to build.