NRC Sees White at Prairie Island

Friday, August 19, 2011 @ 01:08 PM gHale

Prairie Island’s unit 1 reactor faces additional scrutiny from federal regulators following a Nuclear Regulatory Commission (NRC) finding related to backup batteries that would not recharge under certain conditions.

Battery chargers installed in 1994 will malfunction if incoming power dropped below a certain voltage, according to NRC documents.

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In that case, they could reset the chargers manually, and plant owner Xcel Energy said its operators have long had procedures available to do so. The NRC, however, upon discovering the condition last year, assigned it a white finding – the agency’s second-lowest adverse finding classification that indicates a low-to-moderate safety concern.

The battery packs can keep remotely operated safety equipment running in the event of a loss-of-power emergency.

“Prior to the NRC identifying the issue in 2010, the need for operator action to diagnose and restore a failed charger had not been identified as a time-critical operator action,” the NRC’s significance determination said. “The operator action was not directed by the emergency operating procedures and was not included in any operator training.”

Prairie Island’s unit 1 reactor in Red Wing, MN, faces additional scrutiny from federal regulators.

Prairie Island’s unit 1 reactor in Red Wing, MN, faces additional scrutiny from federal regulators.

Switching to backup diesel power is one situation that could reduce voltage to the chargers and cause them to “lock up.”

Xcel said they replaced the equipment in question in May, and they will replace a similar charger in unit 2 during its next refueling. Prairie Island operates two Westinghouse pressurized water reactors generating roughly 550 megawatts each 28 miles southeast of Minneapolis, MN.



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