The company that owns the North Anna Power Station says it has restored off-site electrical power, which is used to cool the spent fuel and keep it from overheating and melting down. The plant had been running on backup diesel generators after yesterday's earthquake. From a Dominion statement:
As designed, four diesel generators supplied power to the station while the off-site power was unavailable. One of the four generators was taken off-line to repair a generator coolant leak, but a fifth generator at the station was activated to replace it until the offsite power was restored. Repairs are complete to the diesel generator.
The company tells us North Anna is designed for a 6.2 magnitude earthquake, with an unspecified measure of safety built in beyond that. Yesterday's quake measured 5.8. To give you a sense of scale, a 6.0 earthquake would be 10 times more powerful than a 5.0 one.
More: The Hill quotes a different Dominion spokesperson with a lower estimate for the plant's design, of 5.9 to 6.1.