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Published: Monday, 3/15/2010

Davis-Besse having problems with current reactor head

BY TOM HENRY
BLADE STAFF WRITER

OAK HARBOR, Ohio - Only six years after putting Davis-Besse back in service, FirstEnergy Corp. is having problems with the reactor head it brought down from a mothballed nuclear plant in Midland, Mich., to replace the damaged lid that had led to a worldwide probe of nuclear operations, including reforms nationally.

The replacement device, which had sat idle in Midland for more than 25 years, is made of an alloy being phased out in the nuclear industry. Even so, officials from FirstEnergy and the U.S. Nuclear Regulatory Commission said when it was installed in 2002 that they expected at least 10-15 years of worry-free operation. Davis-Besse got 25 years out of its original reactor head, although investigators learned problems may have been ignored or undetected for at least the last six years that device was used.

An ultrasonic examination of the device on Friday showed several of the 69 control-rod drive mechanism nozzles jutting out of the top of the reactor head to either have cracks or showing signs of potential cracks.

The U.S. Nuclear Regulatory Commission, in a report posted online Monday morning, identified four nozzles with confirmed cracks, two of which appeared to be showing signs of leaking boric acid from the reactor. FirstEnergy stated in a press release that as many as 12 nozzles showed signs of possible cracks, with tests not yet completed on 20 of the 69 nozzles.

Unlike the 2002 discovery of such cracks, though, FirstEnergy appears to have caught the problem in its early stages. The utility said it appears the cracks can be repaired by its France-based contractor, AREVA, one of the world's largest manufacturers of major nuclear plant parts.

"Safety is our number-one goal, and we are committed to ensuring the structural integrity of the equipment before restarting the plant," Barry Allen, Davis-Besse site vice president, said in a prepared statement. "We have begun a comprehensive investigation to determine the underlying cause, and have secured nuclear contractor AREVA to make the repairs."

No danger exists to the public unless Davis-Besse is put back into operation in substandard condition, a violation of federal NRC rules. That's what happened in 2000 and possibly in earlier restarts, according to a joint investigation by the NRC and the U.S. Department of Justice which resulted in a record $33.5 million in fines being assessed against the utility and sanctions being taken against two former workers, as well as an in-house investigation that resulted in numerous firings.

That event has been described by federal officials as one of the greatest cover-ups in nuclear history. It led to changes in how plants are regulated nationally, and assessments by numerous countries overseas.

FirstEnergy, charged multiple times by the NRC for withholding information from the government in that case, has vowed to never have a repeat of that incident. The utility said it made good on that promise by reporting the latest problem at the first sign of trouble.

Indeed, the NRC has lauded FirstEnergy for safely operating Davis-Besse since the regulator allowed the utility to put the plant back into operation six years ago this month. That restart came following a record two-year outage which included not only technical fixes, but evidence that FirstEnergy executives had improved the plant's workplace atmosphere, or safety culture, so that employees and contractors would have a greater sense of assurance they would be taken seriously if they identified problems they saw.

Davis-Besse has been offline since Feb. 28 for normal refueling and maintenance. Although FirstEnergy did not reveal the length of the outage, they typically last four to six weeks.

Nuclear reactors must be refueled once every 18 months to two years, depending on the type of uranium in their fuel. During those outages, thousands of inspections and repairs are done - mostly ones, such as ultrasonic testing of the reactor head and its nozzles - which cannot be performed while the plant is in service.

One of the most significant aspects of the latest problem isn't just the existence of cracks, but the type of them.

Officials are trying to determine if any of the nozzles have circular-shaped - known as circumferential - cracks in them. Those follow a 360-degree pattern and make nuclear reactors more susceptible to releasing radioactive steam, because they compromise the integrity of the nozzles so much they can pop off like champagne corks when a plant is operating.

Those type of cracks were first discovered in France in the 1980s. They were found for the first time in the United States in 2001 at the Oconee nuclear plant in South Carolina, then at Davis-Besse in 2002.

Officials have said the massive degradation of Davis-Besse's old reactor head probably would have never been discovered if a search hadn't been underway for those type of cracks. Before the Davis-Besse incident of 2002, few utilities - including FirstEnergy - did bare-metal inspections of their reactor heads at each outage.

When FirstEnergy peeled back the insulation off its old reactor head in April of 2002, it discovered a problem never before seen in the nuclear industry. Enough acid from the reactor had escaped through nozzle cracks to pool up on the steel reactor head and burn a pineapple-shaped cavity through six inches of metal. The NRC knew at the time that acid occasionally leaked through nozzles, but the assumption had always been that it vaporized upon contact with the steel reactor heads. Davis-Besse's reactor had been operating at 605 degrees prior to the 2002 shutdown, hotter than any other commercial reactor and 20 degrees hotter than the industry average.

No such damage has been identified as a result of the latest cracks.



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