【東日本大震災/発生から10日目】<更新12>原発への対応進む Japan makes progress at nuclear plant







Second explosion at Fukushima nuclear plant

Update 0815 GMT 14 March 2011
The site causing greatest concern is reactor No. 3 at Fukushima-Daiichi, whose plutonium-uranium fuel mix poses a greater radiological risk than that of reactor no. 1. Chief cabinet secretary Yukio Edano said at 8 pm local time on Sunday that water levels within the pressure vessel could no longer be confirmed to be increasing and that there was a "high possibility" that a valve used to vent steam was malfunctioning. Earlier in the day, Tepco had warned that an explosion like that at reactor No. 1 was possible.


1300 GMT, 13 March 2011
As fears grow of an explosion at the number 3 reactor in the Fukushima-Daiichi nuclear power plant, Japanese prime minister Naoto Kan said in a press conference that the disaster was the worst since the atomic bombing of Hiroshima and Nagasaki in the second world war.

Unlike the uranium-based Fukushima number 1, the number 3 reactor uses a mixture of plutonium oxide and uranium oxide. In the event of a meltdown, plutonium is considered more dangerous than uranium alone because of its increased volatility and its reactive, "neutronic" effects.

Michael Bluck, a nuclear engineer at Imperial College London, told New Scientist that plutonium is used because it increases the efficiency of power generation. "It improves the burn up, so you get more energy out of the fuel than if you just use uranium dioxide (UO2). Plutonium dioxide enhances burn up in normal situations in a controlled reactor, so it may result in even greater heat generation in the event of a meltdown than is the case with UO2 alone. It's why plutonium is used in nuclear weapons, because it is more reactive and produces more energy."
Inperial London Collegeで原子力エンジニアのMichael Bluck氏はNewScientistの取材に応え、以下のように述べた。プルトニウムは自発的中性子放射率が高いことから、原発で利用されている。プルトニウムは燃焼を進め、酸化ウランを利用する場合よりも、より多くのエネルギーを取り出すことができる。酸化プルトニウムは、制御下の炉内では通常燃焼を促進するため、炉心が溶解した状況においても、酸化ウランのみを利用する場合よりも、より多くの熱量を生み出してしまうと思われる。

Bluck notes that plutonium is produced anyway in a "UO2 only" reactor, as part of the fission process. Adding plutonium at the beginning just gives us more.

The danger is that in the event of a meltdown there would be even greater generation of heat, with the additional demands of cooling. Metallic plutonium is a serious fire hazard, Bluck added, further complicating the situation.



福島第1原発事故 避難範囲、なぜ国内外で違うのか 


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The Evacuation Zones Around the Fukushima Daiichi Nuclear Plant

Estimates of Potential Exposure Define U.S. Evacuation Zone

The American Embassy recommended on Wednesday that Americans within 50 miles of the Fukushima reactors evacuate, based on an analysis by the Nuclear Regulatory Commission. The recommendation was based on a model that predicts potential radiation levels depending on whether the containment vessels remain intact, weather patterns, and other factors. Here are the results of the model on March 16.
Japanese and American Evacuation Zones
About 2 million people live within 50 miles of the plant. This is a much larger area than that established by the Japanese, who have told everyone within 12 miles to evacuate and those between 12 and 19 miles to take shelter.





Workers at the Fukushima Daiichi nuclear plant say they are close to restoring electricity to the stricken facility. Meanwhile low levels of radioactive contamination have been detected in some food products from the Fukushima prefecture. Japanese authorities say they are considering a ban. 



Alexander Ananenkov, boss of Russian energy firm Gazprom, says supplying Europe with 60m cubic metres of pipeline gas will free up 40,000 tonnes of LNG. Reuters quoted him as saying: "It is possible to do immediately, right now. Such large scale swap operation between Russia and the European Union will provide real help for Japan."

Food Contamination Fears Could Harm Japanese Brands

TOKYO — Japan’s list of casualties, already long, could soon include two of the country’s iconic brands: sushi and Kobe beef.
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The Japanese Health Ministry said Saturday that it had detected elevated levels of radiation in spinach and milk at farms up to 90 miles from Japan’s crippled nuclear reactors. The ministry did not make reference to any contaminated farm animals, seafood or fishing grounds in Japan. And no food exports from Japan have failed quality tests being done by other countries.












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