(post 8/23 3:41pm- please note information is preliminary)
North Anna Nuclear Power Plant (located very near the epicenter of today’s earthquake) declared an Unusual Event following today’s earthquake. It has been reported that both units (2 unit site) shut off their reactors and disconnected from the grid. While I don’t know the specific cause of their shutdowns, the emergency level (Unusual Event or UE) is a sign that things are a-ok in Central Virginia.
The systems for generating electricity for the grid are not designed to handle earthquake loads. So a shutdown is not a reliable sign of safety problems.
North Anna did lose offsite power, which is also not considered a seismically reliable (“earthquake proof”) component. It makes the response more annoying, but it is not a big safety issue. Land (phone) lines to plant are down, but there are satellite phones on site for safety related backup communications (assuming cells, etc are not working).
All nuclear power plants in the United States are designed for the largest estimated earthquake in the area plus additional margin. While seismic scientists have gotten their share of criticism this year, structural engineers are pretty good at overcompensating by over-designing everything.
Update @ 7:25 pm
North Anna actually declared an ‘Alert’, the second lowest emergency level- my initial report was from unconfirmed media accounts. This declaration is based upon the loss of power from the grid. All the emergency diesels are reported to be operating normally. Several other plants declared procedurally driven ‘Unusual Events,’ but no other plants shut down.
The safety systems at nuclear facilities in the US got tested pretty hard by Mother Nature this year. From tornadoes to floods to earthquakes, we saw impressively safe performance. We aren’t resting on our past success. We make sure we are learning from every event to improve our performance- and to provide you safe and reliable power.