Sunday, April 26, 2009

Braidwood nuclear reactor shut down, malfuction repaired

April 26, 2009

A malfunctioning cooling system control at Exelon Nuclear's Braidwood Generating Station that triggered an automatic shutdown of one of the plant's two nuclear reactors Friday evening has been repaired.

Braidwood Generating Station communications manager Paul Dempsey said repairs were completed at 7:30 p.m. on Saturday, when the reactor was placed back in service. The incident caused no environmental impact, injuries or any disruption of service, and the Nuclear Regulatory Commission was notified of the malfunction, Dempsey said.

The automatic shutdown was triggered when two of four of the electronic panels that monitor temperatures for the cooling system were disabled. The cooling system helps regulate the nuclear reaction in the reaction chamber to make sure uranium fuel rods don't get too hot -- which in the most severe case could cause a meltdown.

Dempsey said one of the electric panels malfunctioned while another was down for regular maintenance. The automatic shutdown slows down the nuclear reaction so the fuel rods cool quickly. It is triggered when two of the four panels are not operating.

The second nuclear reactor at the station continued to operate normally while repairs were made on the reactor that shut down, Dempsey said. Exelon had finished major maintenance and refueling of the operating reactor just last Sunday. Dempsey said "that one is 100 percent."

The last automatic shutdown at Braidwood Generating Station was triggered on Dec. 27, 2008 when an electrical fault in a non-nuclear section of the generating station triggered a shut down, Dempsey said.

-- Jon Krenek and Bill Byrns

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