Did quake effects exceed North Anna design?

Tuesday’s earthquake may have exceeded the design basis for seismic events at the North Anna Power Station in Mineral. That’s according to the Nuclear Regulatory Commission, in an event  report this morning. Tuesday’s earthquake was a 5.8 magnitude quake. The plant was designed to withstand a magnitude 6.2 earthquake. But  monitoring equipment at the plant showed that the quake,  at higher frequencies,  may have exceeded that design.  “Scratch plates” that record ground motion at Unit 1 were sent to a lab for analysis. An NRC spokesman this morning said the agency is  monitoring the post-quake analysis.  The company and the NRC have said there was no damage to critical components of the plant. Meantime, the two reactors at North Anna are shut down as an in-house  evaluation continues. There’s no word on how long the reactors will be shut down.

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