Safe shutdown achieved at Dominion's North Anna site following 5.8 magnitude earthquake

The epicenter was reported the U.S. Geological Survey to be near Mineral, VA, (map) about 15 miles from the plant at a depth of about four miles below the surface.  An aftershock was reported in the area at a magnitude of 2.8 on the Richter scale  soon after.

Dominion reported its reactors shut down safely as a result of a loss of off-site power.  The utility declared an "unusual event" to the NRC.  The Wall Street Journal reported that the power loss was caused by problems in the reactor's switch yard.

"Jim Norvelle, director of media relations for Dominion Resources Inc., operator of the North Anna plant, said its workers inspected the switch yard, through which electricity enters and leaves the installation, and believe problems there caused the nuclear plant to lose access to grid power. When the plant lost access to grid power, it automatically shut down."

"We did lose on-site power, but all the diesel generators are up and running," Dominion spokesman Richard Zuercher said 30 minutes after the quake. "Everything appears to be operating just fine."  Dominion is providing real time updates via its Twitter feed. @DomVAPower  The first official press release from Dominion repeats this information.

NBC Nightly News reported at 18:45 HRs that one of the four emergency diesel generators did not start.  Bloomberg Wire service reported one of the four diesel generators stopped working after startup, David McIntyre, a spokesman for the U.S. Nuclear Regulatory Commission, said in an e-mail.

Zuercher said North Anna's operators were preparing to manually shut down the units after the quake when the power station's operating system automatically powered down both units.

Zuercher told local reporters that diesel generators started as expected to maintain cooling. Dominion's two-unit Surry nuclear power plant, also in the region, was not affected and continues to operate. Reuters reports that Dominion's two reactors at its Surry plant in Gravel, VA, continue to operate normally.

Twelve other reactors in the northeast that measured earthquake effects also reported them to the NRC, but none of them shut down. None of them reactors reported any damage from the earthquake.

Nuclear Regulatory Commission spokesman Roger Hannah told wire services the agency was not immediately aware of any damage at nuclear power plants in the southeast.  The NRC reported that all other nuclear reactors in the northeast continued to operate normally.

The North Anna site is composed of two Westinghouse PWR units that generate approximately 1,800 MW of power.

Unit 1 began commercial operation in June, 1978 and Unit 2 followed in December 1980.

NRC Press Release 2011 08 23; issued 16:45 HRS eastern time, updated at 17:57 HRs

NRC MONITORING ALERT AT NORTH ANNA

FOLLOWING VIRGINIA EARTHQUAKE

No. 11-153

August 23, 2011

The U.S. Nuclear Regulatory Commission headquarters in Rockville, Md., is monitoring an Alert at the North Anna nuclear power plant in Virginia, following today's earthquake in central Virginia. The NRC is also monitoring Unusual Events, the lowest emergency classification, declared at several other Eastern U.S. nuclear power plants. In accordance with agency procedures, the NRC's regional offices in King of Prussia, Pa., and Atlanta have activated their incident response centers. NRC resident inspectors at the affected nuclear power plants will continue to monitor conditions for the duration of the event.

North Anna declared its Alert, the second-lowest of the NRC's four emergency classifications, when the plant lost electricity from the grid following the quake just before 2 p.m. Tuesday. Power is being provided by onsite diesel generators and the plant's safety systems are operating normally. Plant personnel and NRC resident inspectors are continuing to examine plant conditions.

NRC staff in the Maryland headquarters felt the quake and immediately began checking with U.S. nuclear power plants. The NRC is in direct communications with North Anna and is coordinating its response with other federal agencies.

Nuclear power plants are built to withstand environmental hazards, including earthquakes. Even those plants that are located outside of areas with extensive seismic activity are designed for safety in the event of such a natural disaster. The NRC requires that safety-significant structures, systems, and components be designed to take into account the most severe natural phenomena historically reported for the site and surrounding area.

Plants declaring Unusual Events, which indicate a potential decrease in plant safety, include Peach Bottom, Three Mile Island, Susquehanna and Limerick in Pennsylvania; Salem, Hope Creek and Oyster Creek in New Jersey, Calvert Cliffs in Maryland, Surry in Virginia, Shearon Harris in North Carolina and D.C. Cook and Palisades in Michigan. All these plants continue to operate while plant personnel examine their sites.

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