Nuke Back Up after 3 Shutdowns

Wednesday, June 8, 2011 @ 09:06 AM gHale

Unplanned downtime is a nightmare for any manufacturer, but when you have three unplanned nuclear reactor shutdowns in a week, it brings an entirely new level of interest.

Three days after its third unplanned nuclear reactor shut-down, Exelon’s Limerick Generating Station has two working reactors again.

Friday morning, the plant’s Unit 1 generator shut itself down unexpectedly less than a day after the plant’s other reactor, Unit 2, returned to service after two consecutive un-planned shut downs of its own.

Monday morning, Exelon issued a press release announcing that Unit 1 was also back on line, generating electricity.

“Limerick operators and maintenance technicians worked around the clock performing numerous tests to identify the cause of the problem associated with the turbine coming offline and to ensure corrective measures were implemented to prevent recurrence,” Exelon officials said.

It was 5:02 a.m. May 29, when the plant’s other reactor, Unit 2, shut down for the first time.

One day later, while completing testing on the system that controls the opening and closing of turbine valves, the turbine tripped offline again, at 11:50 a.m. May 30.

In February, the same reactor, Unit 2, shut down unexpectedly due to problems with systems related to re-circulating pumps. That shutdown lasted for more than two days.

Unit 2 went back online Thursday, June 2.

The NRC tracks scrams based on the number of times they happen per 7,000 hours of online operation.

“The shutdown would count as a ‘hit on Limerick Unit 1’s Performance Indicator for Unplanned Scrams per 7,000 Hours of Online Operation. As of the end of the first quarter of 2011, that indicator stood at 0.8,” said Neil Sheehan, a spokesman for the Nuclear Regulatory Commission.

“A plant has to have more than three unplanned scrams during that 7,000-hour period to receive increased NRC oversight,” Sheehan said.



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