在「實驗精神」下設計的福島核電一廠

在「實驗精神」下設計的福島核電一廠

2011年4月7日 日本朝日新聞

原文位置：http://www.asahi.com/english/TKY201104060126.html

雖然福島核電二廠的安全性有所提高，但是人們對核電廠安全的過份自信、自滿和高成本的考慮，卻是妨礙改善現在我們看到經已殘破不堪的福島核電一廠之安全問題。

為何災難總不斷出現在福島核電一廠，而距離核電一廠南面幾公里遠的福島核電二廠，在311日本東北大地震和海嘯其間幾乎未受破壞？其主要原由是因為福島核電一廠——日本最老的核電廠——，和福島核電二廠是分別使用了不同的安全設計。

在新潟縣，東京電力公司的柏崎刈羽核電廠的工作人員，為這兩個福島核電廠的安全設計進行了差異分析。

根據他們的分析和東電的資料顯示，這兩個核電廠在設備的安全設計有著明顯的差別，當中包括：電源設備（如後備柴油發電機）、反應爐爐芯的變壓器、以及以注入海水方式來冷卻爐芯過熱的海水泵浦。

東電的文件指出，福島核電一廠渦輪廠房內的後備柴油發電機，除了6號反應爐的外，其餘的後備柴油發電機全都被海嘯淹沒而無法使用。這使得冷卻裝置無法運作。

福島核電一廠失去電力後，反應爐爐芯的反應就變得更難控制，並接二連三的出現了很多嚴重的問題，這還包括反應爐發生氫爆導致一些廠房受到破壞。

而且，隨著反應爐的損毀，不同的放射性物質也被釋放出來。

但福島核電二廠卻沒有發現這樣的問題。

福島核電二廠的後備發電機，是擺放在反應爐爐心的廠房裡。由於反應爐廠房的氣密性較高，所以在海嘯襲擊後，福島核電二廠的後備發電機依然可以繼續運作。

而柏崎刈羽核電廠的，跟福島核電二廠的設計類同，它們也是把後備發電機放置在密閉的反應爐爐心廠房內。

當問及有關福島核電一廠和核電二廠的安全設計差異之問題時，東電總部的人員回應說：「這並不意味我們必須承認這個存在的問題。我們將會進行更詳細的研究來找出問題的所在。」

福島核電一廠是在六十年代至七十年代進行興建。而有關加強廠房防震的工程，則在七十年代至八十年代期間進行。

一位以前時常為東電工作，並參與了這些改善工程的核能工程師向我們表示，東電沒有未考慮過有關後備柴油發電機或海水泵浦的置放位置之問題。

他說：「首先，我們都應為反應爐爐心廠房是建築在一個安全的地方。因為廠房必須能夠抵禦任何預計會衝擊廠房的海嘯高度。」「可是，若他們希望把後備發電機移到廠房內的話，反應爐廠房內根本沒有空間可以讓他們置放這些後備發電機。所以，這意味著他們需要大範圍的修改他們的設計。」

這位工程師說：「當時，沒有任何人認為有必要作這樣的更改。」

在這次大地震而引發的海嘯中，福島核電一廠和二廠都受到14米以上的巨浪衝擊，這是遠超過其安全設計標準的5.2米至5.7米之上限。

由於福島核電一廠的泵浦並未置放在一個密封的建築物內，這些泵浦在受到海嘯衝擊後便無法使用。

儘管福島核電二廠的泵浦都是置放在建築物內，但海嘯仍然摧毀了一號、二號和四號反應爐建築物內的泵浦。只有在三號反應爐的泵浦，可以在海嘯衝擊後繼續冷卻反應爐爐心的溫度。

談到海水泵浦安裝在建築物內部的可能性時，這位前東電工程師表示：「這將會是一個大範圍的修改項目，因為很多管道是藏在這些泵浦的下面，所以牽一髮即動全身。」

一位東電的中層員工還表示，資金是一個很重要問題；這使東電沒有對福島核電一廠進行各種維修和改善的工程。

這名員工說：「福島核電一廠反應爐爐心的設計藍圖，是東芝公司向通用汽車公司（GE）「原封不動」地買過來的。所以，當時東電首先是按照他們的反應爐設計藍圖來進行興建的。」

但在福島核電一廠興建期間，日本又向美國引入新的技術，並向這個擁有更多更先進核能的國家學習相關知識。

所以，福島核電一廠其實是東電的一個「實驗品」。

一位前東電行政人員說：「福島核電一廠是東芝和日立公司不斷摸索GE設計的實驗課程。」

福島核電一廠除六號反應爐外，其他五個號反應爐都是使用由GE開發的Mark I形號之沸水式反應爐。

據消息人士透露，福島核電一廠擺放後備發電機的位置和海水泵浦的構造，也是按GE的設計來放置和製造的。

但核電一廠的六號反應爐卻剛剛相反，它是使用Mark II形號之反應爐。而且，在七十年代中期至九十年代興建的福島核電二廠和柏崎刈羽核電廠，已改用已被改良和較安全的Mark II形號之反應爐。

東芝和日立在後核電一廠得到了有關興建核電廠的經驗後，他們其後便把後備發電機和海水泵浦置放在其他核電廠的廠房裡。

但是，東電依然從未為福島核電一廠進行相關的安全設計改善工程。

其他東電的員工表示，若東電改變核電廠內禦防海嘯的設計，或移動後備發電機的位置的話，這表示東電必須要承認他們過去所做的決定是不夠完善的。

一位技術評論員Kiyoshi Sakurai說，福島核電一廠如此依賴GE的設計，是對福島核電一廠非常危險的。因為美國的設計師們不會跟日本人一樣如斯重視防震和防海嘯的工作。

polly譯。

這篇英文不容易譯，主要是很多名詞我都不懂。若有錯漏，請各位朋友幫忙修訂。謝謝。

Fukushima No. 1 plant designed on 'trial-and-error' basis

2011/04/07 ASAHI.COM

While changes improved safety at the Fukushima No. 2 nuclear power plant, overconfidence, complacency and high costs stymied such action at the now-crippled Fukushima No. 1 plant, according to people familiar with the situation.

The difference in the safety designs was the main reason why the crisis continues to unfold at the Fukushima No. 1 plant--one of the oldest in Japan--while the No. 2 plant a few kilometers south remains relatively unscathed by the March 11 Great East Japan Earthquake and tsunami.

Officials at another Tokyo Electric Power Co. nuclear plant in Kashiwazaki-Kariwa, Niigata Prefecture, analyzed the differences in safety designs at the two Fukushima plants.

According to their analysis and TEPCO sources, there are clear differences in safety levels between the two plants concerning power source equipment, such as emergency diesel generators and transformers at the reactor cores, and pumps used to bring in seawater to remove residual heat from the cores.

TEPCO documents show that the emergency diesel generators located in the turbine buildings at the Fukushima No. 1 plant were flooded by the tsunami and rendered inoperable, except for the one at the No. 6 reactor. This effectively disabled the cooling mechanisms.

After the No. 1 plant lost its power sources, the reactor cores became much more difficult to control, leading to serious problems, including hydrogen explosions that damaged the housing of the reactors.

Radioactive materials have also been emitted from the damaged reactors.

No such problems have been encountered at the No. 2 plant.

The emergency generators at the No. 2 plant were in buildings housing the reactor cores. Because the reactor buildings are much more airtight, the generators at the No. 2 plant continued to function after the tsunami struck.

Emergency generators are also located within the airtight reactor core buildings at the Kashiwazaki-Kariwa plant, which has similar design features to the Fukushima No. 2 plant.

When asked about the differences in the safety designs between the No. 1 and No. 2 plants, an official at TEPCO headquarters said: "This does not mean we have admitted that a problem exists. We will conduct further detailed studies to identify the problems."

The No. 1 plant was built in the 1960s and 1970s. Improvement work was conducted in the 1970s and 1980s to strengthen its resistance to earthquakes.

A nuclear engineer who used to work for TEPCO and was involved in those improvements said no consideration was paid to the location of the emergency diesel generators or the seawater pumps.

"First of all, there was the judgment that the reactor core buildings were in a safe location in relation to the expected height of any tsunami that might strike the plant," the engineer said. "However, even if they wanted to move the generators, there was no space within the reactor building, so that would have meant a major revision in design.

"At the time, no one considered making such changes," the engineer said.

Both the No. 1 and No. 2 nuclear plants were hit by waves more than 14 meters high, well above the expected limits of 5.7 to 5.2 meters estimated in safety designs.

The tsunami rendered inoperable all of the No. 1 plant's pumps, which were also not located within a sealed structure.

Although the pumps at the No. 2 plant were inside buildings, the tsunami crippled the ones to the No. 1, No. 2 and No. 4 reactors. But the pump at the No. 3 reactor continued to cool the reactor core.

Referring to the possibility of installing the seawater pumps inside buildings, the former TEPCO engineer said, "It would have been a major project because various pipes are laid out under the pumps, and so all of that would also have had to be moved."

A midlevel TEPCO official also said money was a big reason why repairs and changes to the No. 1 plant were not made.

"The blueprints for the reactor cores at the No. 1 plant were bought 'as is' by Toshiba Corp. from General Electric Co., so the priority at that time was on constructing the reactors according to those blueprints," the official said.

When the Fukushima No. 1 plant was being built, Japan was importing technology from the United States and learning from a more advanced nuclear power nation.

The No. 1 plant was considered a "learning experience."

A former TEPCO executive said, "The Fukushima No. 1 plant was a practice course for Toshiba and Hitachi Ltd. to learn about GE's design on a trial-and-error basis."

With the exception of the No. 6 reactor, the other five reactors at the Fukushima No. 1 plant are Mark I boiling-water reactors developed by GE.

According to sources, the locations of emergency generators and the seawater pump structure were also based on a GE design.

In contrast, the No. 6 reactor is a Mark II reactor. Moreover, the Fukushima No. 2 plant and Kashiwazaki-Kariwa plant, which were constructed from the mid-1970s to the 1990s, used an improved and safer version of the Mark II reactor.

After Toshiba and Hitachi gained experience in constructing nuclear plants, they located emergency generators and seawater pumps within buildings.

Yet those safety improvements were never reflected in changes at the Fukushima No. 1 plant.

Other TEPCO officials said that changing the anti-tsunami design or moving the location of the emergency generators would have been an acknowledgment that previous decisions were insufficient.

Kiyoshi Sakurai, a commentator on technology issues, said that relying on a GE design also put the Fukushima No. 1 plant at a disadvantage because U.S. designers were not as cautious about earthquakes and tsunami as those working in Japan.