NC Nuke Shut for Cracking

Monday, May 20, 2013 @ 06:05 PM gHale

Shearon Harris’ reactor vessel, which holds the plant’s nuclear fuel and contains the nuclear reaction, shut down after workers found early indications of corrosion and cracking.

The Nuclear Regulatory Commission (NRC) reported Thursday morning that plant officials made the discovery at the Wake County, NC, nuclear plant during a review of ultrasonic data recorded in spring 2012.

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The year-old data, taken by plant owner, Duke Energy Progress, showed a one-quarter-inch flaw in the reactor vessel head, the term for the lid bolted on top of the vessel to maintain superheated water under high pressure.

It’s not clear why it took Progress a year to discover the corrosion, a question the NRC will attempt to answer in its review of the incident. General concerns about vessel head corrosion increased after the discovery in 2002 of a grapefruit-size cavity in the reactor vessel of the Davis-Besse Nuclear Power Station in Ohio, owned by FirstEnergy Corp.

The Davis-Besse incident, considered one of the most serious safety lapses in U.S. nuclear history, resulted in a two-year shutdown, more than $50 million in fines and penalties, and indictments against several utility employees and a contractor.

Conversely, officials caught the Shearon Harris defect early and it did not penetrate the vessel wall, a protective barrier made of carbon steel and measuring about six inches thick. There is no indication radioactive water leaked out of the vessel, the NRC said.

“The reactor is shut down, and our repair plans are in progress,” Progress spokeswoman Kim Crawford said. “There is no impact to public health or safety as a result of this issue.”

Progress had no information on its repair schedule Thursday, but the work is likely to take at least several weeks. Additional information could be available at a public meeting the NRC scheduled at the Holly Springs Cultural Center to present an overview of Shearon Harris’ safety record.

The public meeting was to review the nuclear plant’s 2012 performance; however, NRC staff will be ready to answer questions about the vessel head corrosion and ensuing plant shutdown, NRC spokesman Roger Hannah said.

Because the vessel head repairs will take place in a highly radioactive area, the work will require using remotely operated robotics, Hannah said. He said repairs will involve scraping out corroded material and welding the area, not unlike filling a dental cavity, and technical specialists brought in from an outside engineering company will perform the tasks.

“I’m sure they’ll try to do the repairs as quickly as they can because as long as the plant is shut down they are not making electricity,” Hannah said.

The nuclear plant, which has been generating electricity since 1987, is less than 25 miles from downtown Raleigh.

Duke Energy Progress, formerly known as Progress Energy, is the Raleigh-based subsidiary of Charlotte-based Duke Energy. Duke acquired Progress in July 2012, and Duke officials have since been publicly critical of Progress’ nuclear plant performance during the run-up to the merger.

In February, Duke decided to shut down Progress’ Crystal River plant in Florida after concluding it would have been too expensive to repair. That facility shut down in 2009, never to restart again after the containment building wall repeatedly cracked during a botched attempt to replace two steam generators.

The Shearon Harris vessel head corrosion was in a welded section where a nozzle allows the insertion of a mechanism used to control neutron-absorbing rods inside the reactor.

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