Nuclear power plant safety promises sit on shaky ground
Earthquake prediction is fraught with uncertainty. Ever since the March 2011 Great East Japan Earthquake that crippled the Fukushima No. 1 nuclear plant, researchers have underscored the difficulties in predicting temblors, saying there's no telling just how big an earthquake will be and maintaining that science has its limits.
Prime Minister Yoshihiko Noda gave the go-ahead for the resumption of operations at Kansai Electric Power Co.'s Oi nuclear plant, but both the government and power companies lack regard for this factor of uncertainty in quake prediction. They should admit that situations beyond their expectations can occur, and pour effort into devising disaster prevention measures for a major accident, such as creating evacuation plans.
Before 3.11, the government's Headquarters for Earthquake Research Promotion had predicted a magnitude-7.5 earthquake in the area where the Great East Japan Earthquake struck. But the devastating quake had a magnitude of 9.0 -- 180 times more powerful than this. University of Tokyo professor Robert Geller compares this to predicting light rain but getting hit by a massive typhoon.
Kazuki Koketsu, a professor in the Earthquake Research Institute at the University of Tokyo, commented that the disaster highlighted the "limits of science" in predicting major earthquakes. He pointed out the miscalculated intensity in a publication last year, and stepped down as chief examiner of a government panel discussing quake-resistance measures at nuclear power plants.
After the massive earthquake, the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency (NISA) started focusing more on the prospect of several faults moving in unison to trigger a huge earthquake. But Hiroyuki Fujiwara of the National Research Institute for Earth Science and Disaster Prevention says this development alone is insufficient.
"There are many elements that influence the scale of an earthquake besides joint (fault) movement, and each of them is variable," he says. "A change of just one element can double the scale of an earthquake. There has been an unspoken agreement (among specialists) to take a hard look at just one element without subjecting the second one onwards to the same stringent tests. But presumptions made for the sake of convenience won't cut it. There are faults we don't yet know about. If we don't discuss the uncertainties, we could again overlook something."
Since September last year, Fujiwara has presented such views at hearings held by NISA, but the government's response has been lackluster.
"It leaves you feeling empty," he says.
In a collection of essays released online by the Seismological Society of Japan in May, Tohoku University professor Toru Matsuzawa points out: "There is a great danger of making mistakes when predicting types of earthquakes we have not experienced."
Uncertainties also surround tsunami predictions. Kansai University professor Yoshiaki Kawata made calculations on a theoretical tsunami hitting the lower reaches of the Yodogawa River in Osaka as a result of the next Nankai Earthquake, which seismologists expect to be around magnitude-8.4, and published the results in the March issue of Iwanami Shoten's journal "Kagaku" (Science). Altering seven factors such as the angle at which faults could move, he calculated 20,000 scenarios, and found that in 20 of them, the height of the tsunami would top eight meters. In one case, the tsunami would reach a height of 10 meters. Previously, the largest predicted wave had been 2.5 meters high.
"Each factor is governed by coincidence. Though the rate is low, large figures are conceivable. The height of levees and the like should be decided through public consensus. Measures to reduce the extent of damage when a tsunami breaks the banks of a levee are also vital," Kawata says.
Masaru Kobayashi, head of NISA's Seismic Safety Office, comments, "Views on the uncertainties associated with inland earthquakes were presented at a hearing at the end of May and are being discussed, but the timing of discussion on ocean trench earthquakes has still not been decided."
Delays have also been seen in preparations for future major disasters. Haruki Madarame, chairman of Japan's Nuclear Safety Commission (NSC), told a Diet committee investigating the disaster at the Fukushima nuclear plant in February, "The IAEA (International Atomic Energy Agency) and other bodies are telling us to think about disaster prevention (in the event of a major accident). Our country had stopped doing that."
In March the NSC indicated that in the event of another major nuclear power plant disaster, immediate evacuation would apply to area within "about 5 kilometers of the nuclear plant," while areas within "about 30 kilometers" of the plant would be evacuated in stages. But the exact demarcations for each plant remain unclear. My home is about 7 kilometers away from the Kashiwazaki-Kariwa nuclear plant, but it's unclear whether the area I'm in would be subject to "immediate" or "gradual" evacuation.
Reviews of offsite centers serving as bases for government officials in the event of a nuclear accident have also faced delays. It's feared that these centers could be rendered useless in the event of another major accident because they are too close to the plants.
Against this backdrop, electric power companies have been reluctant to make preparations. In October last year, Kansai Electric Power Co. submitted the results of its "stress test," or safety evaluation, of the No. 3 reactor at its Oi nuclear plant. The first item in the evaluation is how many hours it would take for the plant's nuclear fuel to be damaged in the event of a total blackout. The power company concluded it would take "16 days" -- on the grounds that earthquakes and tsunamis were not part of its considerations. But after NISA pointed out that it was only natural to take earthquake and tsunami into consideration, the utility revised the time down to "one week." With no reinforcements, the time it would take for fuel to be damaged would drop further to just "a few days."
Other power companies submitting the results of stress tests to NISA are also eliminating earthquakes and tsunamis from their calculation on the time it would take for fuel to be damaged. But the whole reason the government imposed stress tests on nuclear power plants in the first place was because of the Fukushima nuclear crisis -- an event triggered by an earthquake disaster. The current stance of power companies casts significant doubt on whether they are seriously considering a major accident.
"They talk about the maximum possible scale of an earthquake, but if we knew that, we would have no difficulties," points out Kenji Satake of the University of Tokyo's Earthquake Research Institute.
If officials admitted the uncertainties in earthquake prediction, then surely they could no longer declare that any countermeasures are "perfect." The government and electric power companies must face this hard reality and work out the level of disaster countermeasures needed to win public understanding. ("As I see it" by Shogo Takagi, Kashiwazaki Bureau)
July 15, 2012(Mainichi Japan)