NRC Notifies Nuclear Plant Owners of Seismic Equipment Issues During Earthquake Near North Anna

An investigation by the Nuclear Regulatory Commission found that some seismic equipment briefly stopped working at Virginia's North Anna nuclear plant during an earthquake in 2011.

No damage occurred, reactor safety systems performed as designed, and both units at the Dominion plant shut down automatically during the 5.8 magnitude quake and power outage. But for eight seconds while emergency diesel generators powered up, part of the control room seismic monitoring equipment shut off because it was not connected to an uninterruptible power supply, the NRC reported in an information notice released Tuesday. Operators declared an alert in response to the earthquake, but the NRC reported the equipment outage prevented them from promptly accessing measurements of the shaking. A measurement of the quake's intensity would be used to determine if precautions such as shutting down the reactors were required, had the units not tripped automatically, according to the agency.

Later, information on the peak shaking period was retrieved and analyzed from a battery-powered Kinemetrics tri-axial seismic time history accelerograph. Nonetheless, the NRC issued the information notice to make other plants aware of the power supply issue potentially affecting other seismic equipment. No action on their part is required. The notice also noted that Kinemetrics SMA-3 monitors at the Surry nuclear plant, also in Virginia, did not trigger following the quake near North Anna. According to the NRC, troubleshooting found that all three sensor masses for the Kinemetrics triggering unit were misaligned and could not trigger at the required level of ground movement.

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  • Anonymous
    Anonymous

    Amatuer hour! "But for eight seconds while emergency diesel generators powered up, part of the control room seismic monitoring equipment shut off because it was not connected to an uninterruptible power supply..." But the next part has this gem: "A measurement of the quake's intensity would be used to determine if precautions such as shutting down the reactors were required, had the units not tripped automatically..." Really!? Keep it running unless the earthquake meets some threshold? Hopefully that is significantly under the magnitude 7 they are supposedly designed to withstand. "... the NRC issued the information notice to make other plants aware of the power supply issue potentially affecting other seismic equipment. No action on their part is required." Nice! Leave it up to the bean counters to decide weather or not UPS's should be installed. " The notice also noted that Kinemetrics SMA-3 monitors at the Surry nuclear plant, also in Virginia, did not trigger following the quake near North Anna. According to the NRC, troubleshooting found that all three sensor masses for the Kinemetrics triggering unit were misaligned and could not trigger at the required level of ground movement." Nobody tests these things!? Thank you, NRC, for keeping us safe (SNARK!).

  • Anonymous
    Anonymous

    It sounds like anonymous has no clue how nuclear power plants work.  A classic nuclear power hater.  An uninformed talking head.  I'm curious to know what anonymous does for a living.  Perhaps I could make some irrelevant marks of my own.  Nah, I'd rather keep my mouth shut when I don't know what I'm talking about.