Unplanned Shutdown at SC Nuke

Monday, October 3, 2011 @ 03:10 PM gHale

A faulty electrical relay caused an unplanned reactor shutdown at the H.B. Robinson Nuclear Plant near Hartsville, SC, early last week.

“We had an automatic plant trip,” said Progress Energy spokesperson Jessica Lambert, who said a faulty electrical relay caused the shutdown. Progress Energy owns and operates the plant. Progress Energy and the Nuclear Regulatory Commission (NRC) are investigating.

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The incident happened at about 11:45 a.m., Lambert said. She said the shutdown occurred when the system that monitors the flow of coolant through the reactor’s coolant system indicated a low flow of coolant in the system.

Plant officials have now determined the incident resulted from a failed electrical relay in the reactor protection system and not from a problem in the coolant system, Lambert said.

The reactor was still down on Wednesday, and Lambert said plant personnel were working to make the needed repairs to bring it back into service soon.

“Of course, the NRC has on-site inspectors here, and we are working very closely with them,” Lambert said.

“It was an automatic shutdown,” said NRC Region II spokesman Roger Hannah. “There was nothing complicated about it.”

Hannah said the reactor system should shut down automatically in the event of a low coolant flow signal. “Everything worked like it was supposed to,” he said.

“We’re following up with our resident inspectors on site.”

The shutdown occurred just days before the NRC was to close a final deficiency finding related to performance at Robinson and problems resulting in unplanned shutdowns occurring in 2009 and 2010 that resulted in heightened oversight of the Robinson facility by the regulatory agency. That finding was to close this past Friday unless additional findings occurred before then.

“That’s something we’ll evaluate,” Hannah said. “It won’t affect what happens on Friday. If we do something, it’ll be after Friday. We’ll review it and look at how it fits into our overall regulatory oversight.”

The NRC said in February it would increase oversight at Robinson in the wake of unplanned reactor shutdowns that occurred on Nov. 6, 2009, and on March 28, Sept. 9 and Oct. 7, 2010.

Those incidents included two electrical fires that occurred on March 28, 2010 that damaged the plant’s electrical system and other equipment. The NRC also cited problems with an emergency diesel generator.

The NRC said poor operator training, failure to follow required procedures and inadequate maintenance all contributed to the plant’s problems.

Plant officials say they have taken significant steps to correct the problems identified by the NRC. Those include changes in leadership, improved training, equipment upgrades and improving workplace behavior.

The Robinson Steam Electric Plant operates one pressurized-water reactor known as Robinson Unit 2. The reactor went into service in March of 1971 and has been producing electricity ever since. The 719-megawatt Robinson facility was the first commercial nuclear reactor in the southeast.

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