Amid all the finger-pointing over the crisis that engulfed the Fukushima No. 1 nuclear power plant, one poor example of decision-making stands out.
Tokyo Electric Power Co., the plant's operator, chose not to consider advances in tsunami research when considering safety measures.
As far back as 20 years or so ago, experts realized that a giant tsunami could pound the region where the nuclear plant is located.
The central government was also slow to mount new inspections of older nuclear plants, partly because it bent to pressure from the business sector which feared higher costs.
The tsunami that hit the Fukushima plant after the March 11 Great East Japan Earthquake was more than 14 meters high, close to three times the 5.4-meter tsunami that TEPCO officials had forecast in considering safety measures.
Plant facilities near the ocean were wrecked. Officials of the Nuclear and Industrial Safety Agency (NISA) said fuel tanks for emergency in-house power generators were destroyed.
In sharp contrast, the Onagawa nuclear power plant, situated about 120 kilometers to the north and operated by Tohoku Electric Power Co., was built to withstand a 9.1-meter tsunami. As a result, it did not sustain major damage.
The Fukushima No. 1 plant lost its outside power source when steel towers carrying transmission lines toppled. Without the backup of emergency generators, the plant went into what is known as blackout condition.
That meant the multilayered safety system, including the emergency core cooling system, did not work, triggering the crisis that has raged ever since.
At a March 13 news conference, TEPCO President Masataka Shimizu said, "The tsunami greatly exceeded our estimates."
However, experts had repeatedly said that TEPCO's estimates were way too low.
Experts attending a June 2009 meeting at the Ministry of Economy, Trade and Industry to discuss a re-evaluation of quake standards for old nuclear plants, got disquieting news.
Yukinobu Okamura, who heads the Active Fault and Earthquake Research Center at the National Institute of Advanced Industrial Science and Technology (AIST), told the gathering, "We have discovered that an incredibly huge (tsunami) that goes way beyond (TEPCO's estimates) has already hit the region."
Okamura said there was a possibility that another giant tsunami could strike the region.
He noted repeatedly that TEPCO's estimates never weighed the possibility that a hugely powerful tsunami could strike again.
Even a NISA safety inspector admitted that TEPCO's estimates were inadequate and would have to be reviewed.
The incredibly huge tsunami that Okamura mentioned hit in 869. Documents from the period suggest it claimed at least 1,000 lives. Researchers have found sand carried by the tsunami in the Sendai plain, which is several kilometers inland.
When the Fukushima No. 1 plant was being designed, little was known about the 869 tsunami.
However, a study by Tohoku Electric Power found that waves as high as 3 meters traveled 3 kilometers inland. A report of that study was submitted in 1990. Subsequent research led to an estimated magnitude of 8.4 for the earthquake that caused the tsunami. That was about six times the energy of the magnitude-7.9 earthquake that TEPCO predicted would hit off the coast where the Fukushima plant is located.
A research team at AIST also uncovered traces of a huge tsunami that hit a wide area stretching from the Tohoku region to the Kanto region in about 1500.
Kunihiko Shimazaki, professor emeritus at the University of Tokyo, said the government's Earthquake Research Committee has begun to assess the likelihood of more giant tsunami pounding coastal areas in the future.
With regard to the tsunami that struck in 869 and 1500, experts do not know whether they were caused by the same type of earthquake that occurred March 11. They say the tsunami triggered by the Great East Japan Earthquake may in fact have been much larger.
That said, a large tsunami hitting the plant was not something totally unexpected.
"Safety inspections must reflect the latest scientific research results," said Yasuhiro Suzuki, a professor at Nagoya University whose specialty is active faults. "Rather than pushing it off into the future, the issue of major tsunami should have been evaluated."
If a reactor core cannot be cooled after it has stopped operations because of an earthquake, the fuel rods will melt, triggering a core meltdown. That increases the chances of hydrogen explosions, which have occurred at the Fukushima plant.
A report in 1997 by Katsuhiko Ishibashi, professor emeritus of seismology at Kobe University, included a passage that eerily echoes what is happening at the Fukushima plant today.
Ishibashi warned of a nuclear accident caused by an earthquake in which damage and radiation contamination would interfere with relief activities.
Ishibashi was concerned that the latest seismology research was not being utilized in any review of the safety of nuclear plants constructed years ago.
For example, the Fukushima plant was designed more than 40 years ago when the existence of a plate boundary off the coast that caused the March 11 earthquake was not yet known.
In the 1990s, government officials began to review anti-quake guidelines for older nuclear plants as well as to ensure that newly constructed nuclear plants could withstand powerful earthquakes.
However, according to Kenji Sumita, professor emeritus of nuclear engineering at Osaka University who once served as acting chairman of the Nuclear Safety Commission of Japan, construction of new nuclear plants went ahead at that time without taking plans for revised safety standards into account.
"There was pressure from the business sector not to change the guidelines until construction plans were completed to a certain degree," Sumita said.
The business sector was concerned that the revision of the guidelines would force electric power companies to scrap or improve existing reactors and review new construction plans, incurring huge costs for them.
"For that reason, a political decision was made to shelve the review into the future," Sumita said.
A thorough review of the anti-quake guidelines was finally made in 2006, 28 years after the old guidelines were first drawn up. A re-inspection of older nuclear plants only began after the new guidelines were in place.
(This article was written by Shunsuke Kimura, Keisuke Katori and Shigeko Segawa.)
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