The Yomiuri Shimbun Apr 17, 2011
This is the sixth and final installment in a series focusing on delays in implementing emergency steps by the government and Tokyo Electric Power Co. to deal with the unprecedented nuclear crisis at the Fukushima No. 1 nuclear power plant.
About 30 minutes after the March 11 earthquake hit, an employee of a Tokyo Electric Power Co. subcontractor working in a building near one of the Fukushima No. 1 nuclear power plant’s reactors heard an ominous roar.
The worker was hearing the giant tsunami that was about to swamp the nuclear plant–an unstoppable wall of water that would easily breach the plant’s breakwater and proceed to wash away the pumps that supplied water to cool the nuclear reactors.
Safe on higher ground, another worker turned to look at the ocean and noticed a huge bowllike object floating out at sea. It was the fuel tank for the emergency diesel generators, he realized.
The Fukushima plant survived the enormous shaking caused by the magnitude-9.0 temblor because of earthquake safety measures put in place long before. Against the tsunami, however, the nuclear power station was almost defenseless.
Most of the power plant sits on ground about 10 meters above sea level. But most of the 13 emergency generators were in the basements of reactor buildings close to the ocean, with only three aboveground. The only generator that survived the tsunami–which are believed to have reached heights of 14 meters or 15 meters–was the one for the No. 6 reactor, which was about 3 meters aboveground.
TEPCO had said in the past that a situation where all the nuclear reactors lost all their power sources would be “unthinkable,” no matter how bad the disaster. On March 11, the unthinkable became reality.
On March 18, TEPCO President Masataka Shimizu issued a statement on the nuclear crisis: “The accident was caused by the violence of nature–a tsunami caused by an unprecedented earthquake–and it is regrettable the crisis has escalated to such an extreme state of affairs.”
The statement effectively shows that TEPCO sees the crisis as due entirely to the massive scale of the natural disaster.
Warnings had been made
Nuclear power specialists had also underestimated the threat posed by tsunami. In February 2007, Haruki Madarame, now chairman of the government’s Nuclear Safety Commission, testified at a lawsuit trying to shut down Chubu Electric Power Co.’s Hamaoka nuclear plant in Shizuoka Prefecture. Madarame, a University of Tokyo professor at the time, was a witness for the defense.
Asked in court why the nuclear plant did not need to prepare for a situation in which all equipment had stopped operating, including emergency power sources, he said: “There needs to be a line drawn somewhere. It’d be impossible to design [a nuclear plant] if engineers had to consider every single possibility.”
However, different experts had warned TEPCO on several occasions about the possibility of a massive tsunami striking the Fukushima No. 1 plant.
Yukinobu Okamura, director of the Active Fault and Earthquake Research Center, harshly criticized TEPCO’s plan to revise its seismic-resistant designs at the Fukushima No. 1 plant at a meeting of an expert panel under the Economy, Trade and Industry Ministry in June 2009. “This plan doesn’t even mention the major tsunami that have happened in the past. I’m not convinced at all,” he said.
About 1,100 years ago, a gigantic earthquake caused tsunami that hit a wide swath of the coast of what is now Miyagi and Fukushima prefectures, according to the National Institute of Advanced Industrial Science and Technology, which oversees the Active Fault and Earthquake Research Center.
Called the Jogan Tsunami, the waves reached about three kilometers or four kilometers inland in the Sendai Plain and other areas, according to the institute, but TEPCO’s new plan made no mention of this historic natural disaster. The expert panel compiled a report the next month, but this also failed to refer to the Jogan Tsunami and concluded it was acceptable to put off making nuclear plants more able to withstand tsunami.
The Diet had also been made aware of the threat. Five years ago, House of Representatives member Hidekatsu Yoshii submitted a written question to the lower house asking whether the government fully grasped the possibility that the nation’s nuclear power plants could lose all power due to an earthquake or tsunami. Yoshii belongs to the Japanese Communist Party.
The response from the government was bureaucratic: “The Economy, Trade and Industry Ministry has inspected the safety of nuclear reactors, and the adequacy of its judgment has been confirmed by the Nuclear Safety Commission.”
Tokai No. 2 fared better
Japan Atomic Power Co.’s Tokai No. 2 plant in Tokaimura, Ibaraki Prefecture, was hit by a 5-meter tsunami on March 11 but the plant’s cooling systems kept functioning.
Learning from the Kashiwazaki-Kariwa nuclear power plant, which was damaged by the 2007 Niigata Prefecture Chuetsu Offshore Earthquake, the firm increased the height of the tsunami the Tokai plant should be prepared for and built a protective wall. The safety measures proved their worth on March 11, protecting two of the plant’s three emergency power sources.
After the March 11 disaster, the government’s Nuclear and Industrial Safety Agency waited about a month before taking any action regarding tsunami. Only on April 9, two days after a magnitude-7.1 aftershock hit the Tohoku region, did the agency instruct power companies to ensure each nuclear plant have at least two emergency generators that would remain functional after a natural disaster.
TEPCO and the government clearly underestimated the warnings that were being sounded over the Fukushima plant’s lack of tsunami-protective measures.
As of Monday, the firm still had the following statement on its Web site: “We have confirmed the safety [of our nuclear plants] by assessing the impact of a tsunami stronger than the largest ever reported using a numerical simulation.”