Federal inspectors are convinced that a nuclear reactor along Lake Erie is safe to operate even though they said Thursday it is not clear why small cracks appeared in a concrete shell that protects the plant.
Tests on the concrete have not given inspectors any reason to keep the plant shut down, said Cynthia Pederson, a regional director with the U.S. Nuclear Regulatory Commission who oversees plants in the Midwest.
"We have a very vigorous inspection we did and it's still ongoing," Pederson told concerned citizens during a public meeting near the Davis-Besse nuclear plant, which is just outside Toledo. "There is a high-level of assurance the containment building is safe."
The NRC allowed the Davis-Besse nuclear plant to begin producing electricity again in early December, less than two months after the first cracks were found.
The plant was shut down for maintenance in October when crews discovered a 30-foot hairline crack in the outer concrete wall that's designed to protect the reactor from anything that might hit it from outside, such as storm debris or an airplane. More cracks were found soon after near the bottom of the 224-foot tall shield structure, leading to closer inspections that found cracks close to the top of the wall.
The commission signed off on restarting the plant following several tests and after its owner, FirstEnergy Corp., assured it that the cracks don't pose a threat.
The commission has given Akron-based FirstEnergy until the end of February to find out what caused the cracks.
Until the cause is known, there's no reason to order closer inspections at other plants with similar concrete shields, Pederson said.
It's possible that the cracks have been around for a while, she said. "Concrete has a tendency to crack," she said.
U.S. Rep. Dennis Kucinich, an Ohio Democrat who has been a longtime opponent of the plant and its owner, has criticized the NRC's decision to allow the plant to reopen until more is known.
He also said FirstEnergy downplayed the scope of the cracks and waited too long to tell the public about where they were found. "This is the first time we've heard FirstEnergy admit this," Kucinich said Thursday.
FirstEnergy officials said they didn't want to release a full report until their investigation was complete.
Howard Whitcomb, who lives in Oak Harbor a few miles from the plant, questioned how regulators could assure anyone the concrete shell is safe without knowing the cause.
"You don't know," he said.
At full power, the plant makes enough electricity for around 750,000 customers, primarily in Ohio. The company's electric system has 4.5 million customers in Ohio, Pennsylvania and New Jersey.
Davis-Besse was shut down this fall to replace an 82-ton reactor head, a steel lid that sits atop the reactor vessel.
FirstEnergy said the new reactor head is made of better material than the former reactor lid that had cracks in its nozzles. The plant was shut down for four months in 2010 for repairs to those cracks that the NRC said were discovered before they could do damage.
The plant also was shut down from 2002 to 2004 because of an acid leak in a different reactor head.
Regulators fined FirstEnergy $5.45 million and the company agreed to $28 million in civil penalties following what the NRC said was the most extensive corrosion found at a U.S. nuclear reactor. The NRC said FirstEnergy misled the agency by providing incomplete and inaccurate information about the acid leak.