During a previous shutdown at Davis-Besse, technicians work from scaffolding to repair components of the reactor.
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OAK HARBOR, Ohio - FirstEnergy Corp. acted responsibly after learning that Davis-Besse's latest nuclear reactor head was breaking down faster than anyone expected.
But the utility probably should have inspected the device more closely when buying it in 2002 from a mothballed plant in Midland, Mich., owned by Consumers Power, the forerunner to Consumers Energy, according to a Nuclear Regulatory Commission document that served as the basis for a public meeting at Oak Harbor High School Thursday.
The meeting was called to discuss the results of a special NRC inspection team's investigation into the unexpected cracks found in Davis-Besse's latest reactor head, a case which had similarities to the historic near-rupture of the plant's head in 2002.
The difference was that there was no evidence of a cover-up in the latest episode, according to the NRC, which also has made it clear that the amount of acid leaking out of the reactor paled in comparison to what happened eight years ago. The 2002 saga led to a record $34 million in fines against FirstEnergy for withholding information from the government, as well as the conviction of two former employees. Both convictions were upheld by an appeals court in July.
In both the 2002 and latest events, nozzles in the nuclear reactor head had cracks.
The latest event appeared to be simple premature aging of the massive steel lid, exacerbated by the Davis-Besse reactor's unusual heat, the agency has said.
Records show Davis-Besse long has had one of the nation's hottest-operating reactors.
According to the document, Mel Holmberg, a senior NRC metallurgical engineer and the special inspection team's leader, said poor carbide distribution was a "significant contributing cause" which kept the latest reactor head from being as tough as FirstEnergy and the NRC believed it was.
The Akron-based utility and the government agency said in the past they thought it could last 15 years. It began breaking down after only six, being put into service when Davis-Besse emerged from its record two-year outage in 2004. The metal lid had been in storage for 25 years before that.
The latest reactor head, like its predecessor, had nozzles made of an inferior metal alloy called Alloy 600. The nuclear industry is in the process of phasing out that alloy in favor of the more robust Alloy 690.
Among those representing the NRC at Thursday's meeting was the agency's Midwest regional administrator, Mark Satorius.
He said plant safety was not compromised, that FirstEnergy identified hairline cracks and leakage in its early stages "well before structural integrity was challenged."
The problem was found after FirstEnergy shut down Davis-Besse on Feb. 28 for normal refueling and maintenance.
Twenty-four of the existing head's 69 nozzles were found to have flaws on them, some so small they could only be detected with ultrasonic equipment.
Repairs have been made.
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