The Nuclear Regulatory Commission has included the Oyster Creek Generating Station on a priority list to conduct an in-depth analysis of updated earthquake risk information.
The NRC reviewed updated earthquake hazard information provided by each plant site in March as part of the NRC's "lessons learned" after the 2011 Fukushima nuclear accident.
“We’ve examined this information to see how a plant’s new quake hazard compares to the ground movement that the plant’s original design process considered,” said Eric Leeds, director of the NRC’s Office of Nuclear Reactor Regulation.
The priority list includes 21 of 59 nuclear plant sites located in the central and eastern United States and one unfinished plant east of the Rocky Mountains.
"The priority grouping is not a risk ranking," NRC spokesman Neil Sheehan said. "The NRC continues to have confidence that plants can operate safely while more analyses are performed. This is based on our understanding of both reactor design and construction, as well as the results of the seismic walkdowns (visual inspections) done at the plants."
The information submitted by the plants showed that their designs are safe for continued operation. If the in-depth analyses show that more "immediate actions" are needed, the NRC will make sure the plants respond appropriately, according to a press release.
“We’re closely following the industry’s response and we’re confident the plants are safe to continue operating," Reed said. If a plant’s new hazard exceeds the original design, the plant has to do a detailed analysis to determine any changes in accident risk from a quake. Plants must also do shorter-term work to see if they should enhance key safety equipment."
It’s important to note that nuclear power plant designs already include a significant margin of safety with respect to the effects of large earthquakes. This margin means the plants can survive stronger ground motion than that used in its seismic design.The priority list considers how a site’s quake hazard transmits energy at frequencies that can affect a plant’s structures, pipes, pumps and related safety systems. A large change between a plant’s original and new hazards at those frequencies was a key consideration in determining a plant’s priority, according to the NRC.
"Oyster Creek has been listed in Priority Group 2," Sheehan said. "The increase in seismic hazard and new ground motion estimates for plants in this category are smaller than Priority Group 1 plants, which must submit a more detailed seismic analysis by June 30, 2017. Priority Group 2 plants will have until Dec. 31, 2019 to submit their more detailed seismic analysis."
Sheehan said the nuclear power plant designs already have a "significant margin" of safety when it comes to large earthquakes.
"This margin means the plants can survive stronger ground motion than that used in its seismic design," he said..