NRC: Battery Charger Problem Warrants White Finding at Prairie Island 1

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

According to documents from the NRC, battery chargers installed in 1994 were shown to malfunction if incoming power dropped below a certain voltage. In that case, the chargers could be reset manually, and plant owner Xcel Energy argued its operators have long had procedures available to do so. Nonetheless, the NRC, upon discovering the condition last year, recently assigned it a white finding – the agency’s second-lowest adverse finding classification that indicates a low-to-moderate safety concern.
Prairie Island nuclear plant. Source: NRC
The battery packs can keep remotely operated safety equipment running in the event of a loss-of-power emergency. The NRC’s significance determination noted, “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 operator action was not directed by the emergency operating procedures and was not included in any operator training” for the complex scenarios that might precipitate charger malfunction.

The Minneapolis Star Tribune cited switching to backup diesel power as one situation that might reduce voltage to the chargers and cause them to “lock up.” The newspaper quoted Xcel as saying the equipment in question was replaced in May, and that a similar charger in unit 2 will be replaced during its next refueling. Prairie Island operates two Westinghouse pressurized water reactors generating roughly 550 megawatts each 28 miles southeast of Minneapolis, Minn.

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  • Anonymous

    Why not just replace the chargers?  They are old anyway.  I have to wonder why not replace equipment giving trouble before the NRC gets there?

  • Bob,

    Good question. From what I can gather, Xcel judged the potential for charger malfunction to be a negligible concern. Obviously the NRC disagreed.

    In a summary of plant management's meeting with the NRC, Xcel made the case that its operators could identify the problem and fix it within an hour. Among the NRC's arguments, the agency's finding was critical of the fact that resetting the chargers was not part of training exercises that envision complex emergencies that might have caused the chargers to lock up.

    Why the equipment wasn't just replaced is anyone's guess. Xcel self-reported the condition in 2010, so perhaps this represents a disagreement between the utility and the regulator as to what exactly constitutes a low-to-moderate safety concern.

    Thanks for reading.


    Nuclear Street News Team

  • Anonymous

    Thanks for the answer, it does not seem like the chargers would be as expensive as a fine from the NRC (if they give out fines, do they?).  Do these utilities have a hard time ordering parts for these facilities?  That is, are the companies raunchy about parts?  Also, I have to wonder:  They say a nuclear power plant has 500 people.  What do they do all day?  I would think a nuclear plant would need fewer people as they are all automatic.  And yes, I am interested in the industry but I am not an engineer.  I have building maintaince background.  Could there be a job for someone like me?

  • It would be great if we know when every part would fail before it does but we don’t. I am sure you would agree with me being in building maintenance. The plants do have a very extensive preventive maintenance program they follow.

    What do nuclear plant personnel do? You can find the typical positions listed here:  Career information can be found here:  I hope this helps!