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Mr. TANAKA, Mitsuhiko (former technical expert of nuclear reactor) wrote the same in magazines, Sekai and Kagaku in April. Regarding the No.1 Reactor, strong quakes might have damaged some pipelines, which lead to loss of coolant. In other words, cooling ability was lost. It is assumed that this loss of coolant caused melt down. Tanaka’s discussion is based on thorough checks of data such as open data by TEPCO, water level in pressure vessel, pressure and pressure within containment. It is highly possible that suppression pool was damaged by strong earthquake shocks in the No.2 Reactor. So this means the loss of function to shut. Mr. Tanaka wrote that this might have lead to leaks of radioactivity and hydrogen, hence hydrogen explosion in the No.2 Reactor. I am a seismologist. Loss of coolant is quite possible from seismological point of view. Shakes at the bottom of the foundation board in the nuclear reactor building, as reported by TEPCO, exceeds shakes presumed by earthquake-resistant structure in NO.2, NO.3 and NO.5 reactors in east-west direction shakes.
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I should like to call your attention, in the Fukushima case, to the fact that duration of shakes was very long. Duration caused by underground seismic waves at magnitude 9.0 level was about 3 minutes. This is very long. Likewise, Fukushima Daiichi was affected by these waves and shakes were long. Therefore, it is possible that lasting and repeated weighting might have caused damages.
On the other hand, it is very important to know that safety against earthquakes of Fukushima Daiichi nuclear power plant was confirmed by the National and Industrial Safety Agency and Atomic Energy Commission in 2009. In other words, it was recognized that stopping, cooling and shutting functions were equipped. But this accident implies that confirmation on safety against earthquakes was wrong.
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The very fact about excess beyond presumed shakes means problems in the guidelines to check on earthquake-resistant structure, revised in 2006. Furthermore, if we assume that this serious accident occurred because of earthquake shakes, then the whole process of deliberations, related results and reliance would be lost. Since 2006/ 2007, back checks have been conducted in all nuclear power plants in Japan. We may have to re-do the whole process all over again.
2）On 30th March, Nuclear and Industrial Safety Agency instructed electric power companies to take emergency safety measures against tsunami with regard to all the nuclear power plants in Japan.
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Measures have been taken but left at least ２ big problems. The afore-mentioned point in ① was disregarded. Measures against tsunami alone do not guarantee safety. Guidelines to check on earthquake resistant structures should be reviewed. Back-checks must be undertaken again. The second problem is that Nuclear and Industrial Safety Agency instructed all the nuclear power plants in Japan to assume big tsunami and loss of all the power sources. This assumption itself is not in accordance with guidelines to review location of nuclear power plants.
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Basic thinking contained in guidelines to review location of nuclear power plants, in particular, conditions of location basically goes as follows: in order to be prepared for an unlikely accident and to secure public safety, basic conditions of location are necessary: location where no past events with incitement to bring big accidents took place, where such events would never occur in future and where events to maximize disasters may be few. It is clearly stated in the guidelines that such basic conditions of location are necessary. But now they urge to assume that big tsunami and related loss of all power sources may cause accidents in all the nuclear power plants in Japan. This is surprising as it is clearly against conditions of location. Based on human common sense and conscience, I think it is crazy to operate nuclear power plants where big tsunami may occur.
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In short, it is only nuclear power plants, just electric power plant, so they say. There is no need, I think, to operate such a dangerous structure where big tsunami may come if its purpose is only to generate electricity.
3）To my regrets, Nuclear and Industrial Safety Agency and Nuclear Safety Commission are now supporting nuclear power plants. I get similar impressions following 3.11 Fukushima Daiichi nuclear power plant’s accident. May I refer to a case I was directory involved? In 2007, Kashiwazaki-Kariwa nuclear power plants were damaged by Chuestu Offshore Earthquakes in Niigata Prefecture and all the 7 reactors stopped. At that time, I participated in discussions of the Niigata Prefecture Sub-Committee as its member. Several researchers pointed out that there existed submarine active fault off the coast of Kashiwazaki-Kariwa nuclear power plants. Nevertheless, TEPCO ignored this very huge submarine active fault. TEPCO picked only a part of the 36km fault and assumed earthquakes at the magnitude 7.0 level to take place there. In case of nuclear power plant, we must consider naturally such issues with safety first in mind, but TEPCO did not respect it.
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4）The Japanese Islands are most unsuitable on earth to build nuclear power plants.
Earthquake plots of the world show that earthquakes occur either on lines or belts. Therefore, the whole Japan is completely covered with belts of earthquake activities. The total area of Japanese territories, territorial waters and exclusive economic zone add up to a little less than 0.3% of the surface of the earth. And about 10% of the total earthquakes concentrate within the same area. Nuclear power plants should not be built on such places. It is a common sense in Europe and the United States of America, as you can see in conditions to restrict nuclear reactors in Germany and the USA and the fact that certain nuclear power plants were shut down due to small active faults which might be treated like a trash in Japan. It is so common that French and German people in Japan would never build nuclear power plants in such places like Japan. I think Japan is not normal.
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Nuclear power plants all over the world have fundamental common problems. Mr. KOIDE Hiroaki (born in 1949 Assistant Professor of Kyoto University Research Reactor Institute) and Mr. GOTO Masashi (Visiting Lecturer, Shibaura Institute of Technology) have pointed out serious problems. But as a realistic seismologist, I think that Japanese nuclear power plants are different from those in France and Germany. What is the difference? Japanese nuclear power plants always come with earthquakes.
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5）For a while we must live with nuclear power plants. Stopping them does not guarantee safety. Spent nuclear fuel is stored in nuclear power plants. This fuel must be kept safely under control for years to come. And earthquakes may occur. Therefore, the Nuclear Power Disaster Counter-Relief Act, Guidelines to Prevent Nuclear Power Plants Disasters and areas covered by EPZ (Emergency Planning Zone) must be revised as soon as possible.
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