Engineers knew tsunami could overwhelm plant
Over the past two weeks, Japanese government officials and Tokyo Electric Power executives have repeatedly described the deadly combination of the most powerful quake in Japan’s history and the massive tsunami that followed as soteigai, or beyond expectations.
When Tokyo Electric president Masataka Shimizu apologised to the people of Japan for the continuing crisis at the Fukushima Daiichi nuclear plant he called the double disaster “marvels of nature ... that we have never experienced before”.
But a review of company and regulatory records shows that Japan and its largest utility repeatedly downplayed dangers and ignored warnings—including a 2007 tsunami study from the company’s senior safety engineer.
“We still have the possibilities that the tsunami height exceeds the determined design height due to the uncertainties regarding the tsunami phenomenon,” Tokyo Electric researchers said in a report reviewed by Reuters.
The research paper concluded that there was a roughly 10% chance that a tsunami could test or overrun the defences of the Fukushima Daiichi nuclear power plant within a 50-year span based on the most conservative assumptions.
But Tokyo Electric did nothing to change its safety planning based on that study, which was presented at a nuclear engineering conference in Miami in July 2007.
Meanwhile, Japanese nuclear regulators clung to a model that left crucial safety decisions in the hands of the utility that ran the plant, according to regulatory records, officials and outside experts.
Among examples of the failed opportunities to prepare for disaster, Japanese nuclear regulators never demanded that Tokyo Electric reassess its fundamental assumptions about earthquake and tsunami risk for a nuclear plant built more than four decades ago. In the 1990s, officials urged but did not require that Tokyo Electric and other utilities shore up their system of plant monitoring in the event of a crisis, the record shows.
Even though Japan’s Nuclear and Industrial Safety Agency, (Nisa) one of the three government bodies charged with nuclear safety, catalogued the damage to nuclear plant vent systems from an earlier earthquake, it did not require those to be protected against future disasters or hardened against explosions.
That marked a sharp break with safety practices put in place in the United States in the 1980s after Three Mile Island, even though Japan modelled its regulation on US precedents and even allowed utilities to use American disaster manuals in some cases.
Ultimately, when the wave was crashing in, everything came down to the ability of Tokyo Electric’s front-line workers to carry out disaster plans under intense pressure.
But even in normal operations, the regulatory record shows Tokyo Electric had been cited for more dangerous operator errors over the past five years than any other utility. In a separate 2008 case, it admitted that a 17-year-old worker had been hired illegally as part of a safety inspection at Fukushima Daiichi.
“It’s a bit strange for me that we have officials saying this was outside expectations,” said Hideaki Shiroyama, a professor at the University of Tokyo who has studied nuclear safety policy. “Unexpected things can happen. That’s the world we live in.”
He added: “Both the regulators and Tepco are trying to avoid responsibility.”
Najmedin Meshkati, a professor of civil and environmental engineering at the University of Southern California, said the government’s approach of relying heavily on Tokyo Electric to do the right thing largely on its own had clearly failed.
“The Japanese government is receiving some advice, but they are relying on the already badly stretched resources of Tepco to handle this,” said Meshkati, a researcher of the Chernobyl disaster who has been critical of the company’s safety record before. “Time is not on our side.”
The revelation that Tokyo Electric had put a number to the possibility of a tsunami beyond the designed strength of its Fukushima nuclear plant comes at a time when investor confidence in the utility is in fast retreat.
Shares in the world’s largest private utility have lost almost three-fourth of their value—$30-billion—since the March 11 earthquake pushed the Fukushima Daiichi nuclear plant into crisis. Analysts see a chance the utility will be nationalized by the Japanese government in the face of mounting liability claims and growing public frustration.
‘Extremely low’ risk
The tsunami research presented by a Tokyo Electric team led by Toshiaki Sakai came on the first day of a three-day conference in July 2007 organised by the International Conference on Nuclear Engineering.
It represented the product of several years of work at Japan’s top utility, prompted by the 2004 earthquake off the coast of Sumatra that had shaken the industry’s accepted wisdom. In that disaster, the tsunami that hit Indonesia and a dozen other countries around the Indian Ocean also flooded a nuclear power plant in southern India. That raised concerns in Tokyo about the risk to Japan’s 55 nuclear plants, many exposed to the dangerous coast in order to have quick access to water for cooling.
Tokyo Electric’s Fukushima Daiichi plant, about 240km north-east of Tokyo, was a particular concern.
The 40-year-old nuclear complex was built near a quake zone in the Pacific that had produced earthquakes of magnitude 8 or higher four times in the past 400 years—in 1896, 1793, 1677 and then in 1611, Tokyo Electric researchers had come to understand.
Based on that history, Sakai, a senior safety manager at Tokyo Electric, and his research team applied new science to a simple question: What was the chance that an earthquake-generated wave would hit Fukushima? More pressing, what were the odds that it would be larger than the roughly six metre wall of water the plant had been designed to handle?
The tsunami that crashed through the Fukushima plant on March 11 was 14 meters high.
Sakai’s team determined the Fukushima plant was dead certain to be hit by a tsunami of one or two meters in a 50-year period. They put the risk of a wave of six metres or more at about 10% over the same time span.
In other words, Tokyo Electric scientists realised as early as 2007 that it was quite possible a giant wave would overwhelm the sea walls and other defences at Fukushima by surpassing engineering assumptions behind the plant’s design that date back to the 1960s.
Company vice-president Sakae Muto said the utility had built its Fukushima nuclear power plant “with a margin for error” based on its assessment of the largest waves to hit the site in the past.
That would have included the magnitude 9,5 Chile earthquake in 1960 that killed 140 in Japan and generated a wave estimated at near six metres, roughly in line with the plans for Fukushima Daiichi a decade later.
It’s been pointed out by some that there could be a bigger tsunami than we had planned for, but my understanding of the situation is that there was no consensus among the experts,” Muto said in response to a question from Reuters.
Despite the projection by its own safety engineers that the older assumptions might be mistaken, Tokyo Electric was not breaking any Japanese nuclear safety regulation by its failure to use its new research to fortify Fukushima Daiichi, which was built on the rural Pacific coast to give it quick access to sea water and keep it away from population centers.
“There are no legal requirements to re-evaluate site related [safety] features periodically,” the Japanese government said in a response to questions from the United Nations nuclear watchdog, the International Atomic Energy Agency, in 2008.
In fact, in safety guidelines issued over the past 20 years, Japanese nuclear safety regulators had all but written off the risk of a severe accident that would test the vaunted safety standards of one of their 55 nuclear reactors, a key pillar of the nation’s energy and export policies.
That has left planning for a strategy to head off runaway meltdown in the worst case scenarios to Tokyo Electric in the belief that the utility was best placed to handle any such crisis, according to published regulations.
In December 2010, for example, Japan’s Nuclear Safety Commission said the risk for a severe accident was “extremely low” at reactors like those in operation at Fukushima. The question of how to prepare for those scenarios would be left to utilities, the commission said.
A 1992 policy guideline by the NSC also concluded core damage at one of Japan’s reactors severe enough to release radiation would be an event with a probability of once in 185 years. So with such a limited risk of happening, the best policy, the guidelines say, is to leave emergency response planning to Tokyo electric and other plant operators.
Prevention, not cure
Over the past 20 years, nuclear operators and regulators in Europe and the United States have taken a new approach to managing risk. Rather than simple defenses against failures, researchers have examined worst-case outcomes to test their assumptions, and then required plants to make changes.
They have looked especially at the chance that a single calamity could wipe out an operator’s main defence and its back-up, just as the earthquake and tsunami did when the double disaster took out the main power and back-up electricity to Fukushima Daiichi.
Japanese nuclear safety regulators have been slow to embrace those changes.
Nisa, one of three government bodies with responsibility for safety policy and inspections, had published guidelines in 2005 and 2006 based on the advances in regulation elsewhere but did not insist on their application.
“Since, in Japanese safety regulation, the application of risk information is scarce in experience ... [the] guidelines are in trial use,” Nisa said.
Japanese regulators and Tokyo Electric instead put more emphasis on regular maintenance and programmes designed to catch flaws in the components of their ageing plants.
That was the thinking behind extending the life of the number-one reactor at Fukushima Daiichi, which had been scheduled to go out of commission in February after a 40-year run.
But shutting down the reactor would have made it much more difficult for Japan to reach its target of deriving half of its total generation of electricity from nuclear power by 2030—or almost double its share in 2007.
The Ministry of Economy, Trade and Industry (Meti) figured it could reach the target by building at least 14 new nuclear plants, and running existing plants harder and longer. Fukushima’s number-one reactor was given a 10-year extension after Tokyo Electric submitted a maintenance plan.
Safety regulators, who also belong to Meti, did not require Tokyo Electric to rethink the fundamental safety assumptions behind the plant. The utility only had to insure the reactor’s component parts were not being worn down dangerously, according to a 2009 presentation by the utility’s senior maintenance engineer.
That kind of thinking—looking at potential problems with components without seeing the risk to the overall plant—was evident in the way that Japanese officials responded to trouble with backup generators at a nuclear reactor even before the tsunami.
On four occasions over the past four years, safety inspectors from Japan and the International Atomic Energy Agency (IAEA) were called in to review failures with backup diesel generators at nuclear plants.
In June 2007, an inspector was dispatched to Fukushima’s number-four reactor, where the back-up generator had caught fire after a circuit breaker was installed improperly, according to the inspector’s report.
“There is no need of providing feedback to other plants for the reason that no similar event could occur,” the June 2007 inspection concluded.
The installation had met its safety target. Nothing in that report or any other shows safety inspectors questioned the placement of the generators on low ground near the shore where they proved to be at highest risk for tsunami damage at Fukushima Daiichi.
‘Get out, get out’
Japanese nuclear regulators have handed primary responsibility for dealing with nuclear plant emergencies to the utilities themselves. But that hinges on their ability to carry them out in an actual crisis, and the record shows that working in a nuclear reactor has been a dangerous and stressful job in Japan even under routine conditions.
Inspectors with Japan’s Nuclear Energy Safety Organisation have recorded 18 safety lapses at Tokyo Electric’s 17 nuclear plants since 2005. Ten of them were attributed to mistakes by staff and repairmen.
They included failures to follow established maintenance procedures and failures to perform prescribed safety checks. Even so, Toyko Electric was left on its own to set standards for nuclear plant staff certification, a position some IAEA officials had questioned in 2008.
In March 2004, two workers in Tokyo Electric’s Fukushima Daini plant passed out when the oxygen masks they were using - originally designed for use on an airplane—began leaking and allowed nitrogen to seep into their air supply.
The risks also appear to have made it hard to hire for key positions. In 2008, Toshiba admitted it had illegally used six employees under the age of 18 as part of a series of inspections of nuclear power plants at Tokyo Electric and Tohoku Electric. One of those minors, then aged 17, had participated in an inspection of the Fukushima Daiichi number-five reactor, Tokyo Electric said then.
The magnitude 9,0 quake struck on Friday afternoon of March 11—the most powerful in Japan’s long history of them—pushed workers at the Fukushima plant to the breaking point as injuries mounted and panic took hold.
Hiroyuki Nishi, a subcontractor who had been moving scaffolding inside reactor number three when the quake hit, described a scene of chaos as a massive hook came crashing down next to him. “People were shouting ‘Get out, get out!’” Nishi said. “Everyone was screaming.”
In the pandemonium, workers pleaded to be let out, knowing a tsunami was soon to come. But Tokyo Electric supervisors appealed for calm, saying each worker had to be tested first for radiation exposure. Eventually, the supervisors relented, threw open the doors to the plant and the contractors scrambled for high ground just ahead of the tsunami.
After the wave receded, two employee were missing, apparently washed away while working on unit number four. Two contractors were treated for leg fractures and two others were treated for slight injuries. A ninth worker was being treated for a stroke.
In the chaos of the early response, workers did not notice when the diesel pumps at number two ran out of fuel, allowing water levels to fall and fuel to become exposed and overheat. When the Fukushima plant suffered its second hydrogen blast in three days the following Monday, Tokyo electric executives only notified the prime minister’s office an hour later. Seven workers had been injured in the explosion along with four soldiers.
An enraged Prime Minister Naoto Kan pulled up to Tokyo Electric’s headquarters the next morning before dawn. “What the hell is going on?” reporters outside the closed-door discussion reported hearing Kan demand angrily of senior executives.
Errors of judgement by workers in the hot zone and errors of calculation by plant managers hampered the emergency response a full week later as some 600 soldiers and workers struggled to contain the spread of radiation.
On Thursday, two workers at Fukushima were shuttled to the hospital to be treated for potential radiation burns after wading in water in the turbine building of reactor number three. The workers had ignored their radiation alarms thinking they were broken.
Then Tokyo electric officials pulled workers back from an effort to pump water out of the number-two reactor and reported that radiation readings were 10-million times normal. They later apologised, saying that reading was wrong. The actual reading was still 100 000 times normal, Tokyo Electric said.
The government’s chief spokesperson was withering in his assessment. “The radiation readings are an important part of a number of important steps we’re taking to protect safety,” chief Cabinet secretary Yukio Edano told reporters. “There is no excuse for getting them wrong.”
Vents and gauges
Although US nuclear plant operators were required to install “hardened” vent systems in the 1980s after the Three Mile Island incident, Japan’s Nuclear Safety Commission rejected the need to require such systems in 1992, saying that should be left to the plant operators to decide.
A nuclear power plant’s vent represents one of the last resorts for operators struggling to keep a reactor from pressure that could to blow the building that houses it apart and spread radiation, which is what happened at Chernobyl 25 years ago. A hardened vent in a US plant is designed to behave like the barrel on a rifle, strong enough to withstand an explosive force from within.
The US Nuclear Regulatory Commission concluded in the late 1980s that the General Electric designed Mark I reactors, like those used at Fukushima, required safety modifications.
The risks they flagged, and that Tokyo did not heed, would come back to haunt Japan in the Fukushima crisis.
First, US researchers concluded that a loss of power at one of the nuclear plants would be one of the “dominant contributors” to the most severe accidents. Flooding of the reactor building would worsen the risks. The NRC also required US plants to install “hard pipe” after concluding the sheet-metal ducts used in Japan could make things much worse.
“Venting via a sheet metal duct system could result in a reactor building hydrogen burn,” researchers said in a report published in November 1988.
In the current crisis, the failure of the more vulnerable duct vents in Fukushima’s number one and number-three reactors may have contributed to the hydrogen explosions that blew the roof off the first and left the second a tangled hulk of steel beams in the first three days of the crisis.
The plant vents, which connect to the big smokestack-like towers, appear to have been damaged in the quake or the tsunami, one Nisa official said.
Even without damage, opening the vulnerable vents in the presence of a build-up of hydrogen gas was a known danger. In the case of Fukushima, opening the vents to relieve pressure was like turning on an acetylene torch and then watching the flame “shoot back into the fuel tank”, said one expert with knowledge of Fukushima who asked not to be identified because of his commercial ties in Japan.
Tokyo Electric began venting the number-one reactor on March 12 just after 10am. An hour earlier the pressure in the reactor was twice its designed limit. Six hours later the reactor exploded.
The same pattern held with reactor number three. Venting to relieve a dangerous build-up of pressure in the reactor began on March 13. A day later, the outer building—a concrete and steel shell known as the “secondary containment”—exploded.
Toshiaki Sakai, the Tokyo Electric researcher who worked on tsunami risk, also sat on a panel in 2008 that reviewed the damage to the Kashiwazaki-Kariwa nuclear plant. In that case, Tokyo Electric safely shut down the plant, which survived a quake 2,5 times stronger than it had been designed to handle.
Sakai and the other panelists agreed that despite the successful outcome the way the ground sank and broke underground pipes needed for firefighting equipment had to be considered “a failure to fulfill expected performance”.
Japanese regulators also knew a major earthquake could damage exhaust ducts. A September 2007 review of damage at the same Tokyo Electric nuclear plant by Nisa deputy director Akira Fukushima showed two spots where the exhaust ducts had broken.
No new standard was put in place requiring vents to be shored up against potential damage, records show.
Masashi Goto, a former nuclear engineer who has turned critical of the industry, said he believed Tokyo Electric and regulators wrongly focused on the parts of the plant that performed well in the 2007 quake, rather than the weaknesses it exposed. “I think they drew the wrong lesson,” Goto said.
The March 11 quake not only damaged the vents but also the gauges in the Fukushima Daiichi complex, which meant that Tokyo Electric was without much of the instrumentation it needed to assess the situation on the ground during the crisis.
“The data we’re getting is very sketchy and makes it impossible for us to do the analysis,” said David Lochbaum, a nuclear expert and analyst with the Union of Concerned Scientists. “It’s hard to connect the dots when there are so few dots.”
In fact, Japan’s NSC had concluded in 1992 that it was important for nuclear plant operators to have access to key gauges and instruments even in the kind of crisis that had not happened then. But it left plans on how to implement that policy entirely to the plant operators.
In the Fukushima accident, most meters and gauges were taken out by the loss of power in the early days of the crisis.
That left a pair of workers in a white Prius to race into the plant to get radiation readings with a handheld device in the early days of the crisis, according to Tokyo Electric.
They could have used robots to go in.
Immediately after the tsunami, a French firm with nuclear expertise shipped robots for use in Fukushima, a European nuclear expert said. The robots are built to withstand high radiation.
But Japan, arguably the country with the most advanced robotics industry, stopped them from arriving in Fukishima, saying such help could only come through government channels, said the expert who asked not to be identified so as not to appear critical of Japan in a moment of crisis. - Reuters