Article 2012.4.2 (Mainichi): 風知草:宙に浮く燃料プール=山田孝男 – In light of further nuclear risks, economic growth should not be priority

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風知草:宙に浮く燃料プール=山田孝男

 大震災以来のおびただしい批判、検証、反省もむなしく、原発の安全をチェックする行政は後退し続けている。

その証拠に、今週から原子力安全・保安院と原子力安全委員会の予算はゼロ。取って代わるはずの「原子力規制庁」は法案が国会に滞留し、発足できない。つまり、監督官庁の存在感がさらに薄らいだ。

予算は「その目的の実質に従い、執行できる」(予算総則14条2)から、暫定存続の旧組織は新組織の予算を流用できるとはいえ、士気は上がらない。各府省のもたれ合い、与野党の不決断、何ごとも東京電力任せの実態は相変わらずだ。

福島第1原発4号機の核燃料貯蔵プールが崩壊する可能性について考えてみる。震災直後から国内外の専門家が注視してきたポイントである。

東電は大丈夫だというが、在野の専門家のみならず、政府関係者も「やはり怖い」と打ち明ける。どう怖いか。

4号機は建屋内のプールに合計1535本、460トンもの核燃料がある。建屋は崩れかけた7階建てビル。プールは3、4階部分にかろうじて残り、天井は吹っ飛んでいる。

プールが壊れて水がなくなれば、核燃料は過熱、崩壊して莫大(ばくだい)な放射性物質が飛び散る。アメリカの原子力規制委員会もフランスの原子力企業アレバ社もこの点を強く意識した。

「福島原発事故独立検証委員会」(いわゆる民間事故調)報告書は、原発事故の「並行連鎖型危機」の中でも4号機プールが「もっとも『弱い環』であ ることを露呈させた」と書く。政府がまとめた最悪シナリオ(同報告書に収録)も4号機プール崩壊を予測。さらに各号機の使用済み燃料も崩壊し、首都圏住民 も避難を迫られるというのが最悪シナリオだ。

震災直後、原発事故担当の首相補佐官に起用された馬淵澄夫元国土交通相(51)は、4号機の地下からプールの底までコンクリートを注入し、チェル ノブイリの「石棺」のように固めようとした。が、プール底部の調査で「強度十分」と見た東電の判断で見送られ、支柱の耐震補強工事にとどめた。

当時の事情を知る政府関係者に聞くと、こう答えた。

「海水を注入しており、部材の健全性(コンクリートの腐食、劣化)が問題。耐震強度の計算にも疑問がある。応急補強の間にプールから核燃料を抜く というけど、3年かかる。それまでもつか。(石棺は)ダムを一つ造るようなもので高くつく。株主総会(昨年6月)前だったから、決算対策で出費を抑えよう としたと思います」

原発推進は国策だが、運営は私企業が担う。政府は東電を責め、東電は「国策だから」と開き直る。「国策民営」の無責任体制は変わらない。

民間事故調の報告書は市販開始3週間で9万5000部出たそうだ。1冊1575円もするというのに。体面や営利に左右されない体系的説明に対する国民の飢えを感じる。

東北・関東で震度5級の地震が続いている。最悪の事態を恐れる者を「感情的」と見くだす不見識を受け入れることはできない。リスク軽視で経済発展を夢想する者こそ「現実的」という非常識に付き合うわけにはいかない。(毎週月曜日掲載)

In light of further nuclear risks, economic growth should not be priority

The government continues to take regressive steps in spite of the torrent of criticism it has received and the lessons that should have been learned since the Great East Japan Earthquake and tsunami triggered a nuclear disaster.

This is evidenced in the fact that starting this week, which marks the beginning of a new fiscal year, the Nuclear and Industrial Safety Agency (NISA) and the Nuclear Safety Commission of Japan (NSC) have no budget. The new nuclear regulatory agency that was supposed to begin operations on April 1 in NISA’s stead is now floundering amid resistance in the Diet from opposition parties. In other words, government agencies overseeing nuclear power now have an even more diminished presence.

According to Japan’s general budget provisions, funds for a new government organization can be diverted to existing government organizations if the money is being used for its original purpose. The situation doesn’t do much for morale, however. Back-scratching relationships between government ministries, the indecision of both the ruling and opposition parties, and the unchanging fact that much of the current crisis is still left in the hands of plant operator Tokyo Electric Power Co. (TEPCO) remains the same.

One of the biggest issues that we face is the possibility that the spent nuclear fuel pool of the No. 4 reactor at the stricken Fukushima No. 1 Nuclear Power Plant will collapse. This is something that experts from both within and outside Japan have pointed out since the massive quake struck. TEPCO, meanwhile, says that the situation is under control. However, not only independent experts, but also sources within the government say that it’s a grave concern.

The storage pool in the No. 4 reactor building has a total of 1,535 fuel rods, or 460 tons of nuclear fuel, in it. The 7-story building itself has suffered great damage, with the storage pool barely intact on the building’s third and fourth floors. The roof has been blown away. If the storage pool breaks and runs dry, the nuclear fuel inside will overheat and explode, causing a massive amount of radioactive substances to spread over a wide area. Both the U.S. Nuclear Regulatory Commission (NRC) and French nuclear energy company Areva have warned about this risk.

A report released in February by the Independent Investigation Commission on the Fukushima Daiichi Nuclear Accident stated that the storage pool of the plant’s No. 4 reactor has clearly been shown to be “the weakest link” in the parallel, chain-reaction crises of the nuclear disaster. The worse-case scenario drawn up by the government includes not only the collapse of the No. 4 reactor pool, but the disintegration of spent fuel rods from all the plant’s other reactors. If this were to happen, residents in the Tokyo metropolitan area would be forced to evacuate.

Former Minister of Land, Infrastructure, Transport and Tourism Sumio Mabuchi, who was appointed to the post of then Prime Minister Naoto Kan’s advisor on the nuclear disaster immediately after its outbreak, proposed the injection of concrete from below the No. 4 reactor to the bottom of the storage pool, Chernobyl-style. An inspection of the pool floor, however, led TEPCO to conclude that the pool was strong enough without additional concrete. The plans were scrapped, and antiseismic reinforcements were made to the reactor building instead.

“Because sea water was being pumped into the reactor, the soundness of the structure (concrete corrosion and deterioration) was questionable. There also were doubts about the calculations made on earthquake resistance as well,” said one government source familiar with what took place at the time. “It’s been suggested that the building would be reinforced, and spent fuel rods would be removed from the pool under those conditions. But fuel rod removal will take three years. Will the structure remain standing for that long? Burying the reactor in a concrete grave is like building a dam, and therefore expensive. I think that it was because TEPCO’s general shareholders’ meeting was coming up (in June 2011) that the company tried to keep expenses low.”

Promotion of nuclear power is a national policy, and yet the operation of nuclear reactors lies in the hands of private corporations. The government pushes the blame on TEPCO, while TEPCO dodges responsibility with the excuse that nuclear energy promotion is a government policy. This system of irresponsibility hasn’t changed.

In the three weeks after the Independent Investigation Commission on the Fukushima Daiichi Nuclear Accident’s report became available to the public, 95,000 copies had been sold; this, despite the fact that they run 1,575 yen a piece. It’s a testament to the public’s thirst for a systematic explanation that is not affected by appearances or interests.

Earthquakes in the neighborhood of level-5 on the seismic intensity scale continue to occur even now in the Tohoku and Kanto regions. We cannot accept the absurd condescension of those who fear the worse-case scenario, labeling them as “overreacting.” We have no time to humor the senseless thinking that instead, those who downplay the risks for the sake of economic growth are “realistic.” (By Takao Yamada, Expert Senior Writer)

(Mainichi Japan) April 2, 2012

 

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