Japan in Their Own Words (JITOW)/日本からの意見

Issues on the accident of Fukushima Daiichi nuclear power reactors and the future direction of the nuclear power generation
WATANABE Hiroshi  / Former researcher at the National Institute for Environmental Studies

October 13, 2014
After the Tohoku Earthquake of the magnitude 9.0 on March 11, 2011 and following the accident of Fukushima Daiichi Nuclear Power Reactors, 3.5 years have passed. As I watched the TV at the time of the accident, I thought Japan was completely cursed. There seems to be a slow recovery from the damage caused by the earthquake thanks to the effort of the inhabitants, but the damage caused by the nuclear accident will remain long. In addition to the fission products (F.P.) scattered over a wide area of Tohoku and Kanto, the reactors which suffered from the accident still contain decay heat and huge amount of radioactivity preventing anyone from accessing the inside of the reactor containers.

In the Fukushima Daiichi site, there are 4 reactors in questions, 1F1, 1F2, 1F3 and 1F4, in addition to the 1F5 and 1F6 located in the north and undamaged, and the melt down occurred at 1F1, 1F2 and 1F3. That is, most of the debris of the fuel and F.P. are out of the pressure vessel and some out of the reactor container.

Recently the Japanese government released to the public a huge amount of the records based on the talks by the people involved in this accident. Among the various people's talks, the most striking was the one by Mr. Yoshida, who was the former chief of the Fukushima Daiichi, deceased last year. His talk describes vividly what happened at the Fukushima Daiichi Site, and how "lucky" we were not to have reached a situation where there would have been more serious contamination of the Tohoku and Kanto area. If we had been "unlucky" , we would have faced even more dire consequences.

The damaged nuclear power reactors released various F.P. such as I131, Sr90, Cs134, Cs137 and radioactive rare gases. The F.P.'s, which have relatively shorter half life time and stronger radioactivity such as I131, caused serious contamination damages to the neighborhood of Fukushima. On the other hand, those having longer half life time such as Cs137 still keep the radioactivity in the area surrounding the Fukushima Daiichi. The estimated amount of the released total Cs 137 is estimated 1.5*1016 Bq., which is 2 % of the total Cs 137 generated in the 3 reactors ( 7*1017 Bq, at the time of the accident) based on the official statement. Please note that this released amount of Cs137 is about 150 times of Cs137 released by the atomic bomb of Hiroshima, although slightly less than that from Chernobyl. As for the external dose rate, it was more than 10 µSv/hr at some area of Iitate, located 30 km northwest of Fukushima Daiichi and about 0.15 µSv/hr at Tsukuba where I lived, 200 km south southwest. (Back ground dose rate in Japan is much less than 0.1 µSv/hr.) And the problems of the accident still remain unresolved both inside and outside of the reactors. I believe it is high time we gave up nuclear power generation.

But, Prime minister Abe mentioned on September 7, 2013 at the International Olympic Committee that the Fukushima Daiichi Nuclear Power Reactors are "under control", which helped the decision to host the Olympic Game in Tokyo in 2020. However, even Tokyo Electric Power Company (TEPCO) immediately denied this assertion. What an irresponsible statement our Prime Mister made! Recently, the Japanese Government is going to restart the operation of the nuclear power reactors that has been completely stopped. Against the restart of the Sendai nuclear power reactors, I submitted a public comment, but there was no answer from the Government. Furthermore, the exportation of the nuclear power plants to the Asian countries is planned by the Abe administration.

The world has already experienced three major accidents of nuclear power reactors, Three Mile Island, Chernobyl and Fukushima. Who can deny the possibility of the forth in the near future? And who will be responsible for the safety of nuclear power reactors scattered worldwide?

Hiroshi Watanabe, PhD. in the Nuclear Engineering, Tokyo University, was Aster (Japanese optical senior on board NASA's Terra Satellite) Ground System Project Manager at ERSDAC (Earth Remote Sensing Data Analysis Center) and GOSAT(Greenhouse gases Observing Satellite) Project Office Manager at NIES (National Institute for Environmental Studies).
The English-Speaking Union of Japan

渡辺  宏 / 元国立環境研究所研究員 

2014年 10月 13日



ダメージを受けた原子炉はI131, Sr90, Cs134, Cs137や希ガスなど多種のF.P.を放出した。F.P.のうち、I131のように、比較的短い半減期を持ち、強い放射能を持つものが原子炉周辺に強い汚染被害を与えた。一方、Cs137のように、比較的長い半減期を持つものは福島周辺で現在もまだ放射能を維持している。公式に発表された、推定される全Cs137の放射能は 1.5x1016 ベクレルで、3原子炉中で生成された全Cs137 ( 7 x 1017 ベクレル、事故時に換算)の約2%に当たる。注目して頂きたいのは、福島第一の場合の放出量は、Cs137換算で、チェルノブイリの場合よりは少ないが、1945年の広島の原爆の際の放出量の150倍程度にもなっている、と言う点である。一方、放出された放射能による外部被曝線量率について言えば、福島第一から北西約30kmの所にある飯舘村では、10 µSv/hr(マイクロシーベルト毎時)を超える所もあり、私が住んでいた南南西200km のつくばでも、0.15 µSv/hr程度あった。(いずれも事故当時に換算、日本の平均的な線量率は0.1 µSv/hrより遥かに低い。)つまり、原子炉の中でも外でも事故の問題は未解決のまま残っている。もう我々は、原発による発電をあきらめる時期に来ているのではないか、と思う。



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English Speaking Union of Japan > Japan in Their Own Words (JITOW) > Issues on the accident of Fukushima Daiichi nuclear power reactors and the future direction of the nuclear power generation