Progress Energy's Shearon Harris nuclear plant in Wake County was one of a dozen nationwide to declare an unusual event after Tuesday's earthquake, but plant operators barely felt the tremor and found nothing amiss after a thorough inspection.
State and local officials have evacuation plans in place for a major emergency, but the 5.8 magnitude earthquake was not felt by many of the engineers and technicians inside the Shearon Harris plant, said Progress spokeswoman Julia Milstead.
Plant officials declared an "unusual event" at 2:06 p.m. on Monday, following the Nuclear Regulatory Commission's criteria for ranking emergencies. An unusual event is the lowest of four emergency levels, and even so, it met only two of the the NRC's three criteria.
The seismic tremors were not strong enough to trigger the plant's earthquake monitors, even though the temblor was felt by some at the plant's administrative offices and shook up people throughout the Triangle.
Shearon Harris officials conducted an inspection of the plant and found nothing out of the ordinary. The inspection was a "walkdown" by mechanics, engineers, operators and maintenance workers to check conditions of equipment and structural features.
Progress cancelled the unusual event at 5:57, nearly four hours after it had been declared.
Nuclear plants declared unusual events in Pennsylvania, New Jersey, Maryland, Virginia and in Michigan.
Officials at the twin-reactor North Anna plant near the quake's epicenter in Virginia declared an "alert," the second-lowest emergency alert level.
The tremors shut down the North Anna plant and caused a loss of offsite electricity, forcing that plant to rely on emergency backup diesel generators to run emergency cooling and safety equipment.