Not a few members of the government panel looking into the accident at the Fukushima No. 1 nuclear power plant are skeptical about Tokyo Electric Power Co. pointing the finger of blame at an unprecedented tsunami.
"The claim that tsunami alone caused the accident is nothing but a hypothesis," said panel member Hitoshi Yoshioka, vice president at Kyushu University, who has written a book about the social history of nuclear energy.
"I feel a majority of panel members feel this way. It is close to a common understanding that it would not be good to trust as is TEPCO's analysis that tsunami was the cause of the accident."
The conclusion reached by the panel could have ground-shaking ramifications for other nuclear power plants in Japan.
If the March 11 earthquake is viewed as the main culprit behind the Fukushima nuclear accident, that would mean that other nuclear plants are also vulnerable to large earthquakes.
Such a possibility is not small since about 10 percent of the world's earthquakes occur in Japan.
The government panel is chaired by Yotaro Hatamura, a professor emeritus at the University of Tokyo noted for his work on the "science of failure." The Hatamura panel is scheduled to release its interim report on Dec. 26.
Sources said that report would likely cast strong doubts on TEPCO's repeated claims until now that tsunami was the main cause of the Fukushima nuclear accident.
Panel members apparently feel there is a need to also consider the possibility that major piping at the Fukushima nuclear plant was damaged by the quake even before any tsunami hit the plant.
Such a theory would severely hinder plans by other electric power companies to resume operations at their nuclear power plants after implementing measures to deal with the possibility of a major tsunami. For example, Chubu Electric Power Co. plans to resume operations at the Hamaoka nuclear plant after construction of a coastal levee.
Many questions, however, remain about the relationship between the quake and the subsequent accident at the Fukushima nuclear plant.
For one thing, the only shaking on March 11 that exceeded government anti-quake standards was the east-west shaking at the No. 2 and No. 3 reactors. All the shaking at the No. 1 reactor was within anti-quake standards. Still, the No. 1 reactor was the first where a hydrogen explosion occurred, spewing radioactive materials into the atmosphere.
For that reason, if the Hatamura panel were to take into consideration the possibility that the quake was the main cause of the Fukushima nuclear accident, that would call into question the inspection guidelines for anti-quake design that were revised in 2006 for all nuclear plants in Japan. Such doubts would make even more difficult resumption of operations at those plants.
That possibility is one reason TEPCO and others in the electric power industry are insisting that only the tsunami was to blame for the Fukushima nuclear accident.
According to Hatamura panel member Yoshioka, there is no way of knowing if the quake actually damaged the major piping at the Fukushima plant without conducting an on-site inspection.
That is one reason there is no member of the Hatamura panel who supports without qualification the theory that the quake was the main cause of the accident.
At the same time, there is little support for TEPCO's argument that if a tsunami had not hit, a major accident would not have occurred and that there would be no safety issue at Japan's nuclear plants as long as measures were strengthened against tsunami.
"There are many important weak points in the safety of Japan's nuclear plants so it is implausible that everything would be all right as long as tsunami measures were implemented," said Yoshioka, whose specialty is the history of science. "I feel this is the common understanding of panel members."
There are 10 members of the Hatamura panel and two others who serve as technical advisers.
According to one panel member, between six to eight of the 12 members have doubts about TEPCO's claim that tsunami was the main cause.
Some members, such as Kazuo Oike, the director of the International Institute for Advanced Studies, have said, "The accident would have been unthinkable without the tsunami. Isn't the tsunami the cause of the accident?"
However, at least half of the panel members are taking TEPCO's arguments with a grain of salt.
A major reason for that doubt is an article by Mitsuhiko Tanaka in the September edition of Kagaku (Science) magazine, published by Iwanami Shoten. Tanaka is a former nuclear plant design engineer who was involved in the design of the pressure vessel of the No. 4 reactor at the Fukushima plant.
Copies of the article were distributed to all Hatamura panel members and quite a few read it.
Tanaka's article criticized the computer simulation analysis conducted by TEPCO, which was attached to the Japanese government's report submitted to the International Atomic Energy Agency. He also surmises that piping at the Fukushima plant was damaged by the quake before the tsunami struck, which led to a loss of cooling water to the reactors.
The major defect in the TEPCO analysis in Tanaka's view is that the times used in the computer simulation for the changes in water levels within the core pressure vessel and the changes in pressure within the containment vessel were clearly different from the actual times measured when the accident was unfolding.
The result of the TEPCO analysis is that after the tsunami struck, electric power sources were lost and a hole was burned in the pressure vessel by a meltdown of the nuclear fuel.
However, the times used in that simulation were vastly different from the actual measured times.
In fact, the actual times measured for the changes in water level and pressure as well as the various notes left by workers at the plant indicate a high possibility that some of the major piping in the plant may have been damaged by the quake before the tsunami struck.
Tanaka's views will likely obtain a wider audience because he has been picked to serve on a Diet panel to look into the Fukushima nuclear accident. That Diet panel will be chaired by Kiyoshi Kurokawa, the former president of the Science Council of Japan.
The views of the Hatamura panel will be closely followed by other electric power companies.
Of the 54 nuclear reactors in Japan, only nine are currently operating. Thirty reactors have stopped operations for periodic inspections.
TEPCO and the Federation of Electric Power Companies of Japan have laid out plans to resume operations at those reactors after conducting two stress tests through computer simulation.
The stress tests will show the extent to which the reactors can withstand effects from quakes and tsunami before they are damaged.
On Oct. 28, Kansai Electric Power Co. submitted the first stress test evaluation for the No. 3 reactor at the Oi nuclear plant to the Nuclear and Industrial Safety Agency. The evaluation showed that the reactor would be able to withstand a quake that was 1.8 times stronger than anti-quake standards.
However, in the case of the Fukushima plant, a hydrogen explosion occurred even though the shaking was within the limits of those anti-quake standards.
If there is the possibility that the Fukushima accident was caused by the quake, not only would that call into question the anti-quake standards, but it would also totally destroy the electric power industry's plans to resume operations after conducting stress tests.
Experts have already raised questions about using the stress test as a condition for deciding to resume operations.
On Nov. 14, experts were allowed to express their views in response to the stress test evaluation for the Oi No. 3 reactor.
Hiromitsu Ino, a professor emeritus at the University of Tokyo who specializes in metal materials, said, "It is wrong to link stress tests with the resumption of operations. The Fukushima nuclear accident demonstrates there were defects in safety inspections until now. If stress tests are conducted without revising those procedures first it would lead to confusion in making safety evaluations."
Ino had a further suggestion.
"In order to verify the effectiveness of stress tests, a stress test should be conducted at the Fukushima No. 1 plant where the accident occurred," he said.
In the background to the strong doubts about TEPCO's claim that tsunami was the main cause of the Fukushima accident is the belief that something is wrong about logic that allows for resumption of operations at nuclear plants based on armchair calculations, when no one knows what the real cause of the Fukushima accident was.
At the first meeting of his panel on June 7, Hatamura said, "(The conclusions of this panel) will be able to withstand an evaluation 100 years from now because it will think about future generations."
- « Prev
- Next »