Japanese Rules for Nuclear Plants Relied on Old Science
By NORIMITSU ONISHI and JAMES GLANZ
The lack of attention may help explain how, on an island nation surrounded by clashing tectonic plates that commonly produce tsunamis, the protections were so tragically minuscule compared with the nearly 46-foot tsunami that overwhelmed the Fukushima plant on March 11. Offshore breakwaters, designed to guard against typhoons but not tsunamis, succumbed quickly as a first line of defense. The wave grew three times as tall as the bluff on which the plant had been built.
Japanese government and utility officials have repeatedly said that engineers could never have anticipated the magnitude 9.0 earthquake — by far the largest in Japanese history — that caused the sea bottom to shudder and generated the huge tsunami. Even so, seismologists and tsunami experts say that according to readily available data, an earthquake with a magnitude as low as 7.5 — almost garden variety around the Pacific Rim — could have created a tsunami large enough to top the bluff at Fukushima.
After an advisory group issued nonbinding recommendations in 2002, Tokyo Electric Power Company, the plant owner and Japan’s biggest utility, raised its maximum projected tsunami at Fukushima Daiichi to between 17.7 and 18.7 feet — considerably higher than the 13-foot-high bluff. Yet the company appeared to respond only by raising the level of an electric pump near the coast by 8 inches, presumably to protect it from high water, regulators said.
“We can only work on precedent, and there was no precedent,” said Tsuneo Futami, a former
The intensity with which the earthquake shook the ground at Fukushima also exceeded the criteria used in the plant’s design, though by a less significant factor than the tsunami, according to data Tokyo Electric has given the Japan Atomic Industrial Forum, a professional group. Based on what is known now, the tsunami set off the nuclear crisis by flooding the backup generators needed to power the reactor cooling system.
For some experts, the underestimate of the tsunami threat at
“They had years to prepare at that point, after Kashiwazaki, and I am seeing the same thing at Fukushima,” said Peter Yanev, an expert in seismic risk assessment based in California, who has studied Fukushima for the United States Nuclear Regulatory Commission and the Energy Department.
There is no doubt that when Fukushima was designed, seismology and its intersection with the structural engineering of nuclear power plants was in its infancy, said Hiroyuki Aoyama, 78, an expert on the quake resistance of nuclear plants who has served on Japanese government panels. Engineers employed a lot of guesswork, adopting a standard that structures inside nuclear plants should have three times the quake resistance of general buildings.
“There was no basis in deciding on three times,” said Mr. Aoyama, an emeritus professor of structural engineering at the
Evolution of Designs
When Japanese engineers began designing their first nuclear power plants more than four decades ago, they turned to the past for clues on how to protect their investment in the energy of the future. Official archives, some centuries old, contained information on how tsunamis had flooded coastal villages, allowing engineers to surmise their height.
So seawalls were erected higher than the highest tsunamis on record. At Fukushima Daiichi, Japan’s fourth oldest nuclear plant, officials at Tokyo Electric used a contemporary tsunami — a 10.5-foot-high wave caused by a 9.5-magnitude earthquake in Chile in 1960 — as a reference point. The 13-foot-high cliff on which the plant was built would serve as a natural seawall, according to Masaru Kobayashi, an expert on quake resistance at the Nuclear and
Eighteen-foot-high offshore breakwaters were built as part of the company’s anti-tsunami strategy, said Jun Oshima, a spokesman for
Over the decades, preparedness against tsunamis never became a priority for
Engineers took a similar approach with earthquakes. When it came to designing the
“We left it to the experts,” said Masatoshi Toyoda, a retired
Eventually, experts on government committees started pushing for tougher building codes, and by 1981, guidelines included references to earthquakes but not to tsunamis, according to the Nuclear and Industrial Safety Agency. That pressure grew exponentially after the devastating
Mr. Sumita said power companies, which were focused on completing the construction of a dozen reactors, resisted adopting tougher standards, and did not send representatives to meetings on the subject at the Nuclear Safety Commission.
“Others sent people immediately,” Mr. Sumita said, referring to academics and construction industry experts. “But the power companies engaged in foot-dragging and didn’t come.”
Meanwhile, the sciences of seismology and risk assessment advanced around the world. Although the United States Nuclear Regulatory Commission has come under severe criticism for not taking the adoption of those new techniques far enough, the agency did use many of them in new, plant-by-plant reviews, said Greg S. Hardy, a structural engineer at Simpson Gumpertz & Heger who specializes in nuclear plant design and seismic risk.
For whatever reasons — whether cultural, historical or simply financial — Japanese engineers working on nuclear plants continued to predict what they believed were maximum earthquakes based on records.
Those methods, however, did not take into account serious uncertainties like faults that had not been discovered or earthquakes that were gigantic but rare, said Mr. Hardy, who visited Kashiwazaki after the 2007 quake as part of a study sponsored by the Electric Power Research Institute.
“The Japanese fell behind,” Mr. Hardy said. “Once they made the proclamation that this was the maximum earthquake, they had a hard time re-evaluating that as new data came in.”
The Japanese approach, referred to in the field as “deterministic” — as opposed to “probabilistic,” or taking unknowns into account — somehow stuck, said Noboru Nakao, a consultant who was a nuclear engineer at
“Japanese safety rules generally are deterministic because probabilistic methods are too difficult,” Mr. Nakao said, adding that “the
The science of tsunamis also advanced, with far better measurements of their size, vastly expanded statistics as more occurred, and computer calculations that help predict what kinds of tsunamis are produced by earthquakes of various sizes. Two independent draft research papers by leading tsunami experts — Eric Geist of the United States Geological Survey and Costas Synolakis, a professor of civil engineering at the University of Southern California — indicate that earthquakes of a magnitude down to about 7.5 can create tsunamis large enough to go over the 13-foot bluff protecting the Fukushima plant.
Mr. Synolakis called
The first clear reference to tsunamis appeared in new standards for
“The 2006 guidelines referred to tsunamis as an accompanying phenomenon of earthquakes, and urged the power companies to think about that,” said Mr. Aoyama, the structural engineering expert.
The risk had received some attention in 2002, when a government advisory group, the Japan Society of Civil Engineers, published recommended tsunami guidelines for nuclear operators.
A study group at the society, including professors and representatives from utilities like Tokyo Electric, scrutinized data from past tsunamis, as well as fresh research on fault lines and local geography, to come up with the guidelines, according to a member of the study group who spoke on condition of anonymity, citing the sensitivity of the situation.
The same group had recently been discussing revisions to those standards, according to the member. At the group’s last meeting, held just over a week before the recent tsunami, researchers debated the usefulness of three-dimensional simulations to predict the potential damage of tsunamis on nuclear plants, according to minutes from those meetings. “We took into account more than past data,” the member said. “We tried to predict. Our objective was to reduce uncertainties.”
Perhaps the saddest observation by scientists outside
On the hard-hit island of Okushiri, “most of the populated areas worst hit by the tsunami were bounded by tsunami walls” as high as 15 feet, according to a report written by Mr. Yanev. That made the walls a foot or two higher than
But in a harbinger of what would happen 18 years later, the walls on Okushiri, Mr. Yanev, the expert in seismic risk assessment, wrote, “may have moderated the overall tsunami effects but were ineffective for higher waves.”
And even the distant past was yielding new information that could have served as fresh warnings.
Two decades after
Norimitsu Onishi reported from Tokyo, and James Glanz from
"The master class has always declared the wars; the subject class has always fought the battles. The master class has had all to gain and nothing to lose, while the subject class has had nothing to gain and everything to lose--especially their lives." Eugene Victor Debs
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