PG&E Corp. and Edison International are embarking on the most extensive and costly study of earthquake risks ever undertaken for U.S. nuclear power plants using 3-D seismic technology pioneered by the oil industry.
The utilities plan to spend $128 million and use research gathered at sea to acquire a better understanding of seismic hazards at California’s two atomic plants built along the coast in the most earthquake-prone area of any U.S. reactors.
Answers from the studies will help regulators decide if PG&E’s Diablo Canyon plant and Edison’s San Onofre station that together supply 14 percent of the California’s electricity are safe enough to operate through 2042. Three-dimensional imaging scans, rarely used outside of energy surveys, may raise the bar for safety tests in other nations concerned after Japan’s atomic disaster left its taxpayers with a bill exceeding $130 billion.
“Modern geologic thought sees the movement of the earth in much more complex terms than was understood 30 years ago,” when the reactors were built, said Sam Blakeslee, a Republican state Senator and former Exxon Mobil Corp. seismologist, who helped draft a 2006 California law that spurred the seismic reviews.
Today’s supercomputers and sensors visualize seismic faults not as static lines, rather as overlapping, multi-directional fractures that can cause blocks of rock to pop up, rotate and spin, Blakeslee said in an interview at a San Luis Obispo, California, coffee shop about 12 miles from Diablo Canyon.
Reactor Knocked Offline
Concerns that earlier research may have understated hazards for U.S. nuclear plants from temblors escalated with last year’s Fukushima nuclear meltdowns and a 2007 quake that knocked Japan’s largest nuclear station offline for nearly two years, Blakeslee said. The earlier 6.8 magnitude temblor “very significantly exceeded” the level of seismic activity for which the Kashiwazaki-Kariwa nuclear plant was designed, according to an International Atomic Energy Agency report.
The U.S. Nuclear Regulatory Commission is monitoring the proposed 3-D surveys in California as it drafts new industry guidelines for re-evaluating earthquake risk, Scott Burnell, a commission spokesman, said in an e-mail.
The federal regulator has discovered greater-than-expected seismic risks for some plants in the central and eastern U.S. with studies it conducted with the U.S. Department of Energy and the Electric Power Research Institute, a Palo Alto, California-based research center.
Diablo Canyon, California’s largest atomic plant, was built in a coastal fault zone about 160 miles (257 kilometers) northwest of Los Angeles, the most populous city in a state with the largest economy in the U.S. Rival utility Edison operates San Onofre atomic plant 60 miles north of San Diego.
If Diablo Canyon suffered a Fukushima-style accident, winds could carry the radioactive plume 85 miles southeast to Santa Barbara, leaving a swath of California’s central wine country an uninhabitable wasteland, according to simulations by the National Resources Defense Council, the New York City-based environmental activist group.
California regulators in 2009 prodded the companies to re-assess seismic and tsunami risks to help the state determine whether the two plants are safe and cost-effective to relicense through mid-century, said Barbara Byron, nuclear policy adviser for the California Energy Commission.
PG&E shares have lost 6.5 percent since March 11, 2011, when an earthquake and tsunami set off a chain of events that produced meltdowns at the Fukushima Dai-Ichi power station. Edison advanced 13 percent in the period, while the 42-member Standard & Poors 500 Utilities Sector Index rose 7.4 percent.
PG&E rose 1 percent today to $43.20 at the close in New York. Edison rose 0.9 percent to $42.89.
After the Fukushima disaster, and at the urging of a state-appointed board overseeing its study, PG&E proposed to quadruple its spending to $64.2 million and more than double its offshore survey to about 357 square miles. Edison has revealed few details of its plans.
The Japanese government is preparing a $136 billion bailout package for Tokyo Electric Power Co. after the Fukushima disaster forced about 160,000 people to flee their homes.
PG&E is prepared to spend “hundreds of millions” of dollars on safety upgrades for Diablo Canyon if studies show they are warranted, Anthony Earley, chief executive officer of California’s largest utility owner, said in a February interview.
To critics, the latest seismic reviews are tainted by mistrust that the state’s two largest utility owners aren’t looking hard enough for the truth, given the billions of dollars in assets involved, Blakeslee said. State regulators met this week to consider whether PG&E’s seismic study is adequate.
PG&E is committed to a “very transparent and open public process” that includes public meetings and legislative and regulatory reviews of its seismic risk studies and response, said Jearl Strickland, director of nuclear projects at Diablo Canyon for San Francisco-based PG&E.
Edison, of Rosemead, California, considers the study part of the company’s “ongoing commitment to safety,” said Jennifer Manfre, a spokeswoman, in an e-mail.
The NRC agreed in Fukushima’s wake to wait for the seismic study results before determining whether to grant 20-year extensions to Diablo Canyon’s licenses, which expire in 2024 and 2025. Edison has said it plans this year to decide whether to seek a similar extension for San Onofre after its licenses expire in 2022. San Onofre is offline indefinitely as the NRC investigates leaks and excessive wear on its steam generators.
State officials also want a say in the process since the NRC “has consistently excluded” seismic vulnerabilities “that are not related directly to plant aging,” Byron said in an e-mail.
PG&E said it’s confident the study will quash concerns about Diablo Canyon, fortified to withstand a 7.5 magnitude temblor and already subject to the greatest seismic scrutiny of any U.S. atomic reactor. The company has steadfastly maintained the plant’s defenses far exceed any shaking that area faults may produce.
“The plant is adequately designed to be able to withstand any credible earthquake that could occur in our region,” said Strickland, during a tour of the facility.
Diablo Canyon is dug into the Irish Hills along a cliff, sitting on top of (solid) bedrock that extends out beneath the Pacific Ocean. Built 48 miles west of the San Andreas fault, it’s the only U.S. atomic plant with its own seismic department, yet its earthquake risks aren’t fully understood.
Researchers want to know how the Shoreline fault, discovered in 2008 a half-mile from the plant’s reactors, interacts with the more powerful Hosgri fault, 2.5 miles offshore and first charted by Royal Dutch Shell Plc seismologists as construction began in the early 1970s.
PG&E spent $1.4 billion to bolster the plant during construction after the NRC mandated upgrades to withstand a worst-case Hosgri temblor. The repairs cost another $3.12 billion in the early 1980s after PG&E engineers discovered the earthquake reinforcements were improperly installed, according to a California Public Utilities Commission filing.
Improvements include concrete buttresses about three and a half stories (34 feet) high that fortify the airline hanger-sized building housing Diablo’s turbines and electric generators, Strickland said. Thick steel beams were put in place to hold steam pipes that snake into the turbines. Electrical wires threaded through tubes were bolted to walls.
PG&E’s subterranean ultrasound test, slated to begin in September, will mark the first time the tools of the oil trade will be re-purposed to measure seismic hazards at a U.S. nuclear plant, said Byron, the state energy commission adviser.
Oil Explorer Technology
The company is in talks with Columbia University and the National Science Foundation to rent the Marcus G. Langseth, a research vessel, to complete the offshore survey near Diablo Canyon. Edison asked California ratepayers to fund a similar $64 million seismic survey for San Onofre, 60 miles south of Los Angeles, and may also rent the Langseth, Manfre said in a phone interview.
PG&E still faces political and logistical tangles as it prepares to map an ecologically fragile stretch of coast with trucks, ships, airplanes and blasts from air guns. The company needs permits from eight state and federal agencies that are weighing the threat to wildlife, including migrating whales and harbor porpoises.
PG&E’s study will use sound waves fired by air guns to chart folds, fractures and faults lacing rock and sediment as deep as 7.5 miles, where earthquakes are typically generated, according to state filings.
To get the most accurate image below any point on earth, researchers must gather data extending 10 miles in all directions, Chip Gill, president of the International Association of Geophysical Contractors, said in a phone interview. He compared the process to stepping to the side to look under a table.
The San Luis Obispo Mothers For Peace, which has fought Diablo Canyon since the early 1970s, point to PG&E’s San Bruno pipeline explosion in 2010 to question the company’s reliability in evaluating its own risks.
Anti-nuclear activists like the Alliance for Nuclear Responsibility suggest the seismic study is biased since PG&E has already concluded Diablo Canyon is safe.
“How can one conduct a scientific inquiry if you have a pre-conceived conclusion?” asked David Weisman, outreach coordinator for the San Luis Obispo-based Alliance, in a phone interview. “They’re looking in all the wrong places for things they hope not to find.”
Public confidence in PG&E was shaken after federal and state investigators determined poor management and safety practices led to the pipeline explosion in San Bruno, California, a San Francisco suburb, that killed eight and destroyed 38 homes. The power company hired a new CEO after the disaster and vowed to improve its safety record.
PG&E’s study plans are being vetted by a state-appointed peer review board. The data gathered by the Langseth will be shared with scientists for separate analysis, Strickland said.