Thursday, March 17, 2011
Two years before an immense coastal earthquake plunged Japan into a nuclear crisis, a geologic fault was discovered about a half-mile from a California seaside reactor — alarming regulators who say not enough has been done to gauge the threat to the nation’s most-populous state.
The situation of the Diablo Canyon plant is not unique. Across the country, a spider’s web of faults in the Earth’s crust raises questions about earthquakes and safety at aging nuclear plants, amplified by horrific images from Japan, where nuclear reactors were crippled by a tsunami caused by a 9-magnitude quake.
The Indian Point Energy Center, for example, lies near a fault line 35 miles north of Manhattan; on Wednesday, New York Gov. Andrew Cuomo ordered a safety review at the plant.
But none of the questions are more pressing than in quake-prone California, where about 10 powerful shakers — stronger than magnitude 7 — have hit since 1900.
At issue at Diablo Canyon is not what is known, but what is not.
Preliminary research at the site, which sits on a wave-washed bluff above the Pacific, found its twin reactors could withstand a potential earthquake generated by the recently identified Shoreline Fault, just off the coast.
But that hasn’t satisfied California regulators. Since late 2008, when the undersea crack was identified, they have pressed plant owner Pacific Gas & Electric Co. to conduct sophisticated, independently reviewed studies that they say are needed to fully assess the danger at a site within 200 miles of Los Angeles.
The recently discovered fault is close to, and might intersect with a bigger crack three miles offshore, and the fear is the two faults could begin shaking in tandem, creating a larger quake than either fault would be capable of producing on its own.
“We don’t yet have a firm idea of the hazard posed by the Shoreline Fault,” says Thomas Brocher, director of the Earthquake Science Center at the U.S. Geological Survey in Menlo Park, Calif., who led the team that discovered the fault.
State Sen. Sam Blakeslee, a Republican who has a doctorate in earthquake studies, wants PG&E to pull back an application to extend the plant’s operating license for 20 years until more is known.
“Aging nuclear power plants and large, active fault systems should not be in close proximity. This isn’t exactly rocket science,” Blakeslee says.
The U.S. Nuclear Regulatory Commission and PG&E say the plant is safe and built to withstand a magnitude 7.5 earthquake, the maximum considered possible for the site.
Damage from a Japan-like tsunami is unlikely, because the reactors sit on an 85-foot cliff above the ocean, and fault structure in the area differs from the Pacific Rim.
Critics say the government has moved too slowly to assess possible threats from earthquakes.