Politics & Government

Engineers Double Checking Nuke Plant Sensor

Too much vibration could cause diesel backup generators to shut down incorrectly, according to an filing submitted to the Nuclear Regulatory Commission from the San Onofre Nuclear Generating Station.

San Onofre Nuclear Generating Station staffers have taken vibration sensors offline to double check they work correctly, according to a plant official.

The sensors are responsible for shutting down emergency diesel backup generators; it trips if the generators vibrate too much, which indicates damage to the internal components, according to a document filed May 23 with the Nuclear Regulatory Commission.

The problem is that it's unclear whether the vibration from an earthquake would have tripped the sensors and caused an inappropriate shutdown of the generators in the event the station lost power at the same time a quake happened, said plant spokeswoman Jennifer Manfre in an email.

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Regulators consider this an "unanalyzed condition" and Southern California Edison engineers are still working to figure out whether an earthquake would trip the sensors of not.

The diesel generators are one of several contingency systems that would activate in the event the station lost power, Manfre said.

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