Shizuoka Newspaper June 5, 2002


By Kiyoo Mogi

(The former professor at Tokyo University, the former chairman of Earthquake Prediction Committee and Coordination Committee for Earthquake Prediction)

Nuclear Power Plant Safety in View of Earthquake

Water leak accident at Hamaoka Unit 2

At a little over 2:00 am on May 25, a radioactive water leak was found in the ECCS system at Hamaoka Unit 2 in Shizuoka prefecture, resulting in the shutdown of the plant.

Hamaoka Unit 1 started its operation in 1976, and Unit 2 in 1978. Last November, the operation of Unit 1 was suspended due to its two accidents-pipe rupture caused by hydrogen explosion and water leak from its reactor vessel. Following these accidents, Unit 2, which has the same structure as Unit 1, had its operation suspended and safety measures were implemented such as installing valves on some pipes.

Since the Unit 1 accident, I have written three editorials, explaining how risky it would be to have Hamaoka nuclear power plants being constructed and operate. Since 1969, the seismologists have been pointing out that a M8 earthquake could occur in Tokai area (200km west of Tokyo). Consequently, the government enacted a bill called Special Countermeasures on the Large Scale Earthquake Act, and has established the Earthquake Prediction Committee. I pointed out the danger of the Tokai Earthquake for the first time in 1969, and since then, I have been working for the mitigation of disasters to be caused by the Tokai Earthquake. I had been a committee member of Earthquake Prediction Committee, and the chairperson of the same committee, and become the chairman of the Coordination Committee for Earthquake Prediction.

However, Hamaoka nuclear power plants are located in the very center of the earthquake source region, and furthermore, the Unit 5 is still under construction. It has been 30 years since the Great Tokai Earthquake issue was announced for the first time. In the latter half of these 30 years, I have been tackling this issue as an executive member. Yet, the Chubu Electric Company has never sought for my opinion regarding the siting or safety of the nuclear power plants even for a single time.

There are many nuclear power plants in the world, and most of them are in advanced nations. The US is on the top, followed by France, Japan, and Germany. However, most nuclear power plants are in western nations. Japan, Korea, etc are exceptions. When we take a look at the earthquakes more than M7 in the world in this 100 years, there have been almost no earthquakes in western nations with a number of nuclear power plants, and thus, we can see that their lands are very stable. Even in Korea, there is almost no prominent earthquake in modern age.

Overall Review is Necessary

Compared to other nations in the world, Japan is unique. Japan has the third largest number of nuclear power plants in the world and at the same time, it has seen a number of M7 or more earthquakes occurring in such a small area. Moreover, there is no nation that has four nuclear power plants on the middle of a region where M8 (30 times more than M7 in energy level) earthquake is predicted. It is simply ghastly.

I hear opinions stating that there is no danger because of measures implemented for earthquake resistance on nuclear power plants. I do not understand why anybody can ensure such a theory. A Nuclear power plant has a complex structure, which contains many weak parts in regard to their strength. In the past, the earthquake resistance standards have been revised each time unexpected things took place. Nuclear power plant safety is no exception.

These are the reasons why I insisted that a drastic review should be conducted on Hamaoka nuclear power plants after the Unit 1 accident. However, Chubu Electric did not listen to such kind of voices, and resumed the Unit 2 operation only within six months after the Unit 1 accident.

Agency for Nuclear and Industry Safety (ANIS) in Ministry of Economy, Industry and Trade (METI) gave the approval on the inspection result of the Unit 2, to which Hamaoka town and Shizuoka prefecture were made to agree. It is not a surprising thing that voices of criticism are gathering to Chubu Electric and ANIS after the accident of Unit 2. In the worst case, an accident in Hamaoka would affect almost all the areas of mainland Japan. I would like to stress repeatedly, that Hamaoka issue needs a drastic review from a wide point of view.