Two local nuclear plants are reassessing their ability to withstand an earthquake.
The U.S. Nuclear Regulatory Commission asked for the review after recent seismic data showed a higher earthquake risk in the region.
Peach Bottom Atomic Power Station and Three Mile Island Nuclear Generating Station are among two dozen nuclear plants nationwide that must issue evaluations and reports to the NRC by the end of the year.
"That doesn't mean the plants are unsafe right now. The risk for earth movement affecting the plants is still a low probability," said Neil Sheehan, NRC spokesman.
Peach Bottom and TMI used computer modeling to "get a better picture of what they might be faced with" in the event of a strong earthquake and determined they would need to take some steps to prevent damage, he said.
Those steps may involve improving equipment and making sure backup equipment is able to handle an earthquake, Sheehan said.
"They need to tell us what their interim measures are by the end of the year. We will set deadlines for other upgrades after further evaluations," he said.
Most nuclear plants were designed in the 1960s and 1970s and were built to withstand earthquakes 200 miles away. New data suggests plants should be prepared for earthquakes 400 miles away, Sheehan said.
"But all plants are designed to automatically shut down when there's an earthquake of a certain magnitude," he said.
The NRC asked for the review in the wake of a seismic risk assessment released in 2008, and the massive earthquake in Japan in 2011 that created a tsunami and caused a nuclear meltdown at the Fukushima Daiichi plant.
"We would expect all nuclear plants in the U.S. to be as prepared as possible in the event of a severe earthquake," Sheehan said.
—Reach Candy Woodall at email@example.com.