08/04 TEPCO won't take Chernobyl approach to resolving nuclear power plant crisis （英和）

Tokyo Electric Power Co. (TEPCO) adviser Toshiaki Enomoto is pictured at the company's Tokyo head office. (Mainichi)

It may take 10 years to start removing damaged nuclear fuel from the Fukushima No. 1 Nuclear Power Plant, but the plant's operator is adamant not to bury the damaged reactors while fuel remains in them, a company official has told the Mainichi.

"We will not bury the site while radioactive materials remain. We will definitely remove the fuel," Tokyo Electric Power Co. (TEPCO) adviser Toshiaki Enomoto told the Mainichi in an interview, stressing that the company would not bury the reactors in concrete in a "stone tomb" approach like the one adopted at Chernobyl.

TEPCO chairman Tsunehisa Katsumata has announced plans to decommission the plant's No. 1 through 4 reactors. Normally it takes 20 to 30 years to decommission a reactor, but the process at the Fukushima No. 1 Nuclear Power Plant is expected to take even longer as workers must start by developing specialized equipment to remove damaged fuel.

Enomoto said that for the time being the ongoing process of injecting water into the No. 1, 2 and 3 reactors at the plant was essential.

"There is no other option but to inject water. We want the fuel to stop melting," he said.

The plant's residual heat removal system could take a month to get up and running again, Enomoto said. An additional cooling system will also be constructed but it is expected to take several months before the reactors can be brought to a cold stop.

A facility to purify contaminated water responsible for radioactive leaks to a level where it can be released will be constructed from this month. At the same time measures will proceed to have radioactive material contained within the reactor buildings within a few months, Enomoto said. At this stage, evacuation orders applying to local bodies around the plant are expected to be reviewed.

Enomoto said nuclear fuel at the plant could not be removed using conventional methods for two reasons: The reactor buildings are damaged, and measures are needed to prevent the spread of radiation; and 25 to 70 percent damage has occurred to the fuel rods in the No. 1, 2 and 3 reactors. New methods to remove the fuel must be developed, and it will take 10 years before workers can start removing fuel, he said.

Commenting on TEPCO's response to the disaster, Enomoto said, "Problems that we had not predicted happened one after another. Even inspecting the site has been difficult, and this accumulation of events has been responsible for the work not going as we have hoped."

The U.S. Nuclear Regulatory Commission said that it took five years for workers to be able to open a pressurized container following the Three Mile Island Nuclear Generating Station accident in March 1979, when about 45 percent of the nuclear reactor fuel melted. It was another six years before the removal of nuclear fuel was completed. Dismantling work has still not yet begun.

Enomoto graduated from the University of Tokyo's Faculty of Engineering and entered TEPCO in 1965. He worked at the Fukushima No. 1 Nuclear Power Plant four times, including when the No. 1 reactor was started up on a trial basis in 1970. He resigned as executive vice president and head of the company's nuclear power headquarters in 2002 over the cover-up of nuclear reactor trouble.

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(Mainichi Japan) April 8, 2011

福島第１原発：「燃料棒除去の着手まで１０年」東電顧問


インタビューに答える榎本聡明・東京電力顧問＝東電本店で、山田大輔撮影

　東日本大震災で被災した東京電力福島第１原発について、東電の榎本聡明（としあき）顧問が毎日新聞のインタビューに応じた。原子炉を冷却し、廃炉に不可欠な核燃料の取り出しに着手するまでに約１０年かかるとの見通しを明らかにする一方、「放射性物質を残したまま埋めてしまうことはない。燃料は必ず取り除く」と、住民感情を踏まえ、チェルノブイリ原発のように燃料ごとコンクリートで埋める「石棺方式」は取らないことを強調した。【山田大輔】

　東電の勝俣恒久会長は１～４号機を廃炉にする方針を明らかにしている。通常の廃炉でも２０～３０年かかるとされるが、福島第１の場合、損傷した核燃料を取り出す専用装置開発から始める必要があり、廃炉完了までの期間がさらに長引くことは確実だ。

　榎本顧問は東電本店で取材に応じ、１～３号機で続いている原子炉への注水作業について「水を注入するほかない。燃料がこれ以上溶解するのを食い止めたい」と説明。本来の冷却システム「残留熱除去系」の復旧には少なくとも１カ月かかるとの見通しを示した。予備の冷却システム増設も併せて進め、原子炉内が「冷温停止」と呼ばれる安定な状態になるまでには数カ月かかると述べた。

　放射能漏れにつながっている汚染水の問題については、放射線量を放流できるレベルまで落とす浄化設備を今月中に着工。数カ月後をめどに、放射性物質を原子炉建屋内に閉じ込める対策も並行して進めると述べた。周辺自治体に対する避難・屋内退避指示の解除などは、この段階が検討開始の目安になるとみられる。

　廃炉への課題として榎本顧問は（１）原子炉建屋が損傷しており、まず放射性物質の拡散を防ぐ対策が必要（２）１～３号機の燃料棒が推定で２５～７０％損傷しているため、従来の方法では取り出せない、と指摘。燃料の回収装置を新たに開発し、燃料回収を始めるまでに１０年はかかると述べた。

　事故に対して「我々が予測していなかった問題が次々と出てくる。現場の観察自体が難しく、思うように進まないのが今までの積み重ねだった」と、対応の遅れを振り返った。

　米原子力規制委員会によると、炉心燃料の約４５％が溶融したとされるスリーマイル原発事故（７９年３月）の場合圧力容器のふたが開けられる状態になるまでに５年、さらに燃料取り出し完了までに６年かかった。解体作業はまだ始まっていない。

　榎本顧問は東京大工学部卒、６５年東電入社。福島第１では１号機の試運転（７０年）を含め４回勤務した。副社長・原子力本部長だった０２年、「トラブル隠し」が発覚し引責辞任した。