Japan’s nuclear regulators and the operator of the crippled Fukushima reactors were warned that a tsunami could overwhelm the plant’s defenses and failed to recognize the threat.
The Trade Ministry dismissed evidence two years ago from geologists that the power station’s stretch of coast was overdue for a giant wave, minutes from a government committee show. Tokyo Electric Power Co. engineers also didn’t heed lessons from the 2004 tsunami off Indonesia that swamped a reactor 2,000 kilometers (1,200 miles) away in India, even as they advised the nuclear industry on coping with the dangers.
Tokyo Electric’s Dai-Ichi plant withstood the impact of Japan’s record earthquake March 11, only for a wall of water to knock out generators needed to keep its reactors cool. The cost of the miscalculation mounted as explosions and fires at the plant caused radiation leaks that forced the evacuation of more than 200,000 people and contaminated drinking water.
“The Japanese system underestimated the natural threat from the earthquake and tsunami,” said Pierre Zaleski of University Paris Dauphine and a former French Atomic Energy Commission member. “They really haven’t taken these threats seriously enough, and they haven’t moved fast enough.”
Underscoring the Japanese government’s failure to foresee the risk posed by tsunamis to nuclear power plants is the country’s national report on nuclear safety, filed with the International Atomic Energy Agency in September 2010. The 194-page document discusses detailed earthquake mitigation measures 74 times. Tsunamis are mentioned twice, both times in reference to a working group studying the issue.
Tokyo Electric’s sea-wall defenses for the Dai-Ichi plant were built under the assumption that the coastline on which it sat wasn’t prone to tsunamis higher than 5.5 meters, said Yoshimi Hitosugi, a Tokyo-based company spokesman.
An 8-meter tsunami that hit Japan’s northeast in 869 swept as far as 4 kilometers inland at Sendai Bay, stretching south toward the Dai-Ichi plant, according to at least half a dozen scientific studies spanning more than a decade.
A repeat could occur soon because sediment samples showed the tsunami had a pattern of recurring every 800 to 1,000 years, according to a 2001 report by a research team funded by the government’s Science Ministry.
Minutes of a committee meeting held by the Trade Ministry to assess reactor safety on June 24, 2009, show that Yukinobu Okamura, who heads the government-funded Active Fault and Earthquake Research Center, asked Tokyo Electric why it hadn’t taken on board evidence of the tsunami risk.
“We didn’t think the damage would be that significant,” replied Isao Nishimura, a manager at Tokyo Electric’s nuclear earthquake resistance technology center.
The debate was cut short by an official from the regulator, Nuclear and Industrial Safety Agency, who said the matter needed study. The agency approved the safety report a month later, calling on Tokyo Electric to “take appropriate measures” to adopt lessons from research on tsunami risk.
“The utility bears some responsibility for this, but the regulator didn’t give any guidance,” Okamura said in a March 23 phone interview. “Looking back, I wish I had pressed harder. It’s easy to say after the fact.”
The committee’s focus was on the impact of earthquake vibration and it was turning to tsunamis after, said Yuji Wakamatsu, a spokesman for the nuclear safety agency.
Tokyo Electric engineers were looking at tsunami risk at least as far back as 2005.
The tsunami caused by the December 2004 earthquake off the Indonesian island of Sumatra led to a conference in Tamil Nadu, India, hosted by Kalpakkam nuclear station, which had survived a direct hit.
At the August 2005 forum, Tokyo Electric senior nuclear engineer Toshiaki Sakai delivered a report called “Tsunami Evaluation Method for Nuclear Power Stations in Japan,” according to the IAEA’s website. The company declined to make him available for an interview and Hitosugi said it cannot find the report.
Japan’s delegation gave guidance on coping with tsunami threats and developed a system to evaluate risks and protect reactors, the IAEA said in a report from the conference on its website.
The lesson from the Kalpakkam plant was simple: build high, said S. Krishnamurthy, executive director of operations at Nuclear Power Corp. of India, who was in charge at the time.
“Kalpakkam has been built in such a way that almost all its units, except of course the pump house that pumps sea water, are at an elevation,” he said last week.
Tohoku Electric Power Co.’s Onagawa nuclear power plant was about 75 kilometers closer to the epicenter of the quake, and suffered no critical damage because it was built 15 meters above sea level, spokesman Yoshitake Kanda said.
In both instances, reactors were safely shut down and cooling systems continued to operate.
Tohoku Electric said it’s strengthening preparations against disasters, including keeping a generator car at its nuclear plants at all times in case of power failures, according to a statement yesterday on the utility’s website.
In 2009, Japan’s Nuclear Safety Commission listed the “Seismic Roadmap” as one of its key priorities, with an emergency preparedness program for tsunami as one of the mid-term plans it was working on between 2007 and 2012, according to the commission’s report from February 2009.
Last November, Tokyo Electric hosted the first symposium on seismic safety of nuclear installations at Kashiwazaki, home to the world’s largest nuclear plant which was shut down after a 2007 earthquake caused a fire and spillage of radioactive water. One of four main sessions was on tsunamis, during which IAEA’s Kenta Hibino made a presentation on the global nuclear community’s “work plan for tsunami hazard.”
The IAEA declined to set up an interview with Hibino, saying all its experts were busy dealing with the crisis.
Japan has suffered 195 tsunamis since 400, according to Japan’s Central Research Institute of Electric Power Industry, which produced a report on tsunami threats to nuclear plants on the opposite coast to Dai-Ichi in July 2008. Three in the past three decades had waves of more than 10 meters.
A 7.6-magnitude quake in 1896 off the east coast of Japan created waves as high as 38 meters, while an 8.6-magnitude temblor in 1933 led to a surge as high as 29 meters, according to the U.S. Geological Survey.
Geologist Masanobu Shishikura, a researcher under Okamura who has focused on the 869 tsunami, said he wasn’t surprised historical evidence wasn’t heeded to. When he presented to government officials from two towns on the coast north of Dai-Ichi, the urgency wasn’t clear even to him.
Today, those towns of Higashi Matshushima and Ishinomaki lie in ruins.
“At the time, we thought it was unfortunate they didn’t take us seriously, but we figured it was just a matter of making a better presentation,” Shishikura said. “If only the tsunami had waited a little longer, we might have been ready.”