The Nuclear Regulatory Commission has issued a rare “For the Record” statement intended to assuage public fears about nuclear plant safety in the aftermath of the March 11 earthquake and nuclear disaster in Fukushima, Japan.
The 21⁄2-page statement repeatedly mentions California’s two nuclear power plants and contains assurances that the agency believes Diablo Canyon and San Onofre nuclear plants are safe.
“The Diablo Canyon and San Onofre plants are located in a region that experiences higher levels of seismic activity than most of the United States and are designed accordingly,” the statement reads. “The NRC does not believe the seismic hazards associated with the Diablo Canyon and San Onofre plants can be directly compared to events at Fukushima.”
Such statements are unusual and are used when the agency wants to set the record straight, said Lara Uselding, NRC spokeswoman. It was prompted by thousands of messages, many of them nearly identical, that the NRC received questioning the ability of nuclear plants to withstand severe natural events and asking for “immediate inspections.”
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While the statement focuses on the two California plants, the Pilgrim plant in Massachusetts and the Indian Point plant near New York are also mentioned as targets of the messages. The NRC would not disclose the exact number of messages and which plants they mention.
Diablo Canyon and San Onofre are designed to withstand quakes of 7.5 and 7.0 magnitude respectively. The Pilgrim and Indian Point plants are in less seismically active areas and are designed to withstand 6.0 magnitude quakes but are located close to large population centers.
The main difference between the plant in Japan and the California plants is the fact that the Japanese plant is near a subduction zone, a type of earthquake fault that produces the biggest quakes and large tsunamis, the statement said. The faults around Diablo Canyon are of the strike-slip variety.
Subduction faults are one tectonic plate being pushed under another. Strike-slip faults are where plates slide horizontally past one another.
The Japanese disaster was caused by a 9.0-magnitude quake followed by a tsunami that inundated the plant and knocked out its primary and backup power sources. The NRC statement described this as a combination of highly unlikely natural disasters.
“The NRC believes that it is highly unlikely that a similar combination of events such as those which occurred in Japan could ever occur in the United States, including at the Diablo Canyon and San Onofre nuclear plants,” the statement reads.
The possibility of a combination of disasters, each compounding the other, striking Diablo Canyon was a common concern expressed by the public June 15 at an NRC public hearing in San Luis Obispo. Multiple speakers told NRC officials that the Japanese disaster shows that such an unforeseen disaster is possible.
The NRC statement also outlined the agency’s response since the March 11 disaster. This included inspections of plants’ emergency procedures and resources. An inspection at Diablo Canyon found more than 20 problems, including a cooling pump that did not start, that have since been corrected.
The NRC has also established a senior level task force that will look for lessons to be learned from the Japanese disaster. A report from the task force is due in July.