A nuclear reactor where cracks were discovered in the plant's concrete shell nearly two months ago began producing electricity again Tuesday, despite objections from an Ohio congressman who says unanswered questions are lingering about what happened.
FirstEnergy Corp., the operator of the Davis-Besse plant near Toledo, said it should be at full power later this week.
The plant along Lake Erie 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.
More cracks were found soon after leading to closer inspections.
The U.S. Nuclear Regulatory Commission signed off on restarting the plant after FirstEnergy assured them that the cracks don't pose a threat. Regulators said they've done their own checks and reviewed testing already completed by the plant operator.
U.S. Rep. Dennis Kucinich, an Ohio Democrat who has been a longtime opponent of the plant and its owner, criticized the NRC's decision, saying that it's still not known what caused the cracks or whether it's a bigger problem.
The NRC has given Akron-based FirstEnergy until the end of February to find out what caused the cracks.
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 same plant also was shut down from 2002 to 2004 because of an acid leak in a different reactor head.