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はてなキーワード: Blameとは
結論：大丈夫。
MvK2010
I'm going to copy paste a full blog post of a research scientist at MIT here, who explains the situation at Fukushima much better than anyone else has, his message: no worries.
This post is by Dr Josef Oehmen, a research scientist at MIT, in Boston.
He is a PhD Scientist, whose father has extensive experience in Germany’s nuclear industry. I asked him to write this information to my family in Australia, who were being made sick with worry by the media reports coming from Japan. I am republishing it with his permission.
It is a few hours old, so if any information is out of date, blame me for the delay in getting it published.
This is his text in full and unedited. It is very long, so get comfy.
I am writing this text (Mar 12) to give you some peace of mind regarding some of the troubles in Japan, that is the safety of Japan’s nuclear reactors. Up front, the situation is serious, but under control. And this text is long! But you will know more about nuclear power plants after reading it than all journalists on this planet put together.
There was and will *not* be any significant release of radioactivity.
By “significant” I mean a level of radiation of more than what you would receive on – say – a long distance flight, or drinking a glass of beer that comes from certain areas with high levels of natural background radiation.
I have been reading every news release on the incident since the earthquake. There has not been one single (!) report that was accurate and free of errors (and part of that problem is also a weakness in the Japanese crisis communication). By “not free of errors” I do not refer to tendentious anti-nuclear journalism – that is quite normal these days. By “not free of errors” I mean blatant errors regarding physics and natural law, as well as gross misinterpretation of facts, due to an obvious lack of fundamental and basic understanding of the way nuclear reactors are build and operated. I have read a 3 page report on CNN where every single paragraph contained an error.
We will have to cover some fundamentals, before we get into what is going on.
Construction of the Fukushima nuclear power plants
The plants at Fukushima are so called Boiling Water Reactors, or BWR for short. Boiling Water Reactors are similar to a pressure cooker. The nuclear fuel heats water, the water boils and creates steam, the steam then drives turbines that create the electricity, and the steam is then cooled and condensed back to water, and the water send back to be heated by the nuclear fuel. The pressure cooker operates at about 250 °C.
The nuclear fuel is uranium oxide. Uranium oxide is a ceramic with a very high melting point of about 3000 °C. The fuel is manufactured in pellets (think little cylinders the size of Lego bricks). Those pieces are then put into a long tube made of Zircaloy with a melting point of 2200 °C, and sealed tight. The assembly is called a fuel rod. These fuel rods are then put together to form larger packages, and a number of these packages are then put into the reactor. All these packages together are referred to as “the core”.
The Zircaloy casing is the first containment. It separates the radioactive fuel from the rest of the world.
The core is then placed in the “pressure vessels”. That is the pressure cooker we talked about before. The pressure vessels is the second containment. This is one sturdy piece of a pot, designed to safely contain the core for temperatures several hundred °C. That covers the scenarios where cooling can be restored at some point.
The entire “hardware” of the nuclear reactor – the pressure vessel and all pipes, pumps, coolant (water) reserves, are then encased in the third containment. The third containment is a hermetically (air tight) sealed, very thick bubble of the strongest steel. The third containment is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. For that purpose, a large and thick concrete basin is cast under the pressure vessel (the second containment), which is filled with graphite, all inside the third containment. This is the so-called “core catcher”. If the core melts and the pressure vessel bursts (and eventually melts), it will catch the molten fuel and everything else. It is built in such a way that the nuclear fuel will be spread out, so it can cool down.
This third containment is then surrounded by the reactor building. The reactor building is an outer shell that is supposed to keep the weather out, but nothing in. (this is the part that was damaged in the explosion, but more to that later).
Fundamentals of nuclear reactions
The uranium fuel generates heat by nuclear fission. Big uranium atoms are split into smaller atoms. That generates heat plus neutrons (one of the particles that forms an atom). When the neutron hits another uranium atom, that splits, generating more neutrons and so on. That is called the nuclear chain reaction.
Now, just packing a lot of fuel rods next to each other would quickly lead to overheating and after about 45 minutes to a melting of the fuel rods. It is worth mentioning at this point that the nuclear fuel in a reactor can *never* cause a nuclear explosion the type of a nuclear bomb. Building a nuclear bomb is actually quite difficult (ask Iran). In Chernobyl, the explosion was caused by excessive pressure buildup, hydrogen explosion and rupture of all containments, propelling molten core material into the environment (a “dirty bomb”). Why that did not and will not happen in Japan, further below.
In order to control the nuclear chain reaction, the reactor operators use so-called “moderator rods”. The moderator rods absorb the neutrons and kill the chain reaction instantaneously. A nuclear reactor is built in such a way, that when operating normally, you take out all the moderator rods. The coolant water then takes away the heat (and converts it into steam and electricity) at the same rate as the core produces it. And you have a lot of leeway around the standard operating point of 250°C.
The challenge is that after inserting the rods and stopping the chain reaction, the core still keeps producing heat. The uranium “stopped” the chain reaction. But a number of intermediate radioactive elements are created by the uranium during its fission process, most notably Cesium and Iodine isotopes, i.e. radioactive versions of these elements that will eventually split up into smaller atoms and not be radioactive anymore. Those elements keep decaying and producing heat. Because they are not regenerated any longer from the uranium (the uranium stopped decaying after the moderator rods were put in), they get less and less, and so the core cools down over a matter of days, until those intermediate radioactive elements are used up.
This residual heat is causing the headaches right now.
So the first “type” of radioactive material is the uranium in the fuel rods, plus the intermediate radioactive elements that the uranium splits into, also inside the fuel rod (Cesium and Iodine).
There is a second type of radioactive material created, outside the fuel rods. The big main difference up front: Those radioactive materials have a very short half-life, that means that they decay very fast and split into non-radioactive materials. By fast I mean seconds. So if these radioactive materials are released into the environment, yes, radioactivity was released, but no, it is not dangerous, at all. Why? By the time you spelled “R-A-D-I-O-N-U-C-L-I-D-E”, they will be harmless, because they will have split up into non radioactive elements. Those radioactive elements are N-16, the radioactive isotope (or version) of nitrogen (air). The others are noble gases such as Xenon. But where do they come from? When the uranium splits, it generates a neutron (see above). Most of these neutrons will hit other uranium atoms and keep the nuclear chain reaction going. But some will leave the fuel rod and hit the water molecules, or the air that is in the water. Then, a non-radioactive element can “capture” the neutron. It becomes radioactive. As described above, it will quickly (seconds) get rid again of the neutron to return to its former beautiful self.
This second “type” of radiation is very important when we talk about the radioactivity being released into the environment later on.
I will try to summarize the main facts. The earthquake that hit Japan was 7 times more powerful than the worst earthquake the nuclear power plant was built for (the Richter scale works logarithmically; the difference between the 8.2 that the plants were built for and the 8.9 that happened is 7 times, not 0.7). So the first hooray for Japanese engineering, everything held up.
When the earthquake hit with 8.9, the nuclear reactors all went into automatic shutdown. Within seconds after the earthquake started, the moderator rods had been inserted into the core and nuclear chain reaction of the uranium stopped. Now, the cooling system has to carry away the residual heat. The residual heat load is about 3% of the heat load under normal operating conditions.
The earthquake destroyed the external power supply of the nuclear reactor. That is one of the most serious accidents for a nuclear power plant, and accordingly, a “plant black out” receives a lot of attention when designing backup systems. The power is needed to keep the coolant pumps working. Since the power plant had been shut down, it cannot produce any electricity by itself any more.
Things were going well for an hour. One set of multiple sets of emergency Diesel power generators kicked in and provided the electricity that was needed. Then the Tsunami came, much bigger than people had expected when building the power plant (see above, factor 7). The tsunami took out all multiple sets of backup Diesel generators.
When designing a nuclear power plant, engineers follow a philosophy called “Defense of Depth”. That means that you first build everything to withstand the worst catastrophe you can imagine, and then design the plant in such a way that it can still handle one system failure (that you thought could never happen) after the other. A tsunami taking out all backup power in one swift strike is such a scenario. The last line of defense is putting everything into the third containment (see above), that will keep everything, whatever the mess, moderator rods in our out, core molten or not, inside the reactor.
http://anond.hatelabo.jp/20110314030613
へ続く
http://anond.hatelabo.jp/20100621194920
Firstly let me congratulate your acquisition of a PhD. You have done something that most of us never can.
Considering how successful you are in academia, I believe some people were jealous and picked on your Japanese accents and unsociable sides. I can't blame them, however, to think how daring your feat seemed to them. Let alone receiving a PhD, a good number of us can't even hope to receive a bachelor's degree, not even in our dreams.
And doing so in a foreign country? In a foreign language? That's beyond our imagination.
You have climbed a peak that many others have failed.
If you are still unsure about your sense of humor and accents, maybe you should spend some time traveling and having fun: Normally dry sober days of studying does not improve your communication skills much.
Just have some fun with friends and you will pick up their accents eventually. The rest will be easy.
現実問題として語学の習得に掛かる時間は相当なものでしょうね。
大体人間が普段使う単語数は２５ｋ前後と聞きましたが、教養のある人はこれが４０K以上になる筈です。一単語につき意味は一つではありませんから、一つの言語の完璧な習得に必要な時間は、莫大なものとなります。
私の体感では、才能のない人が大人成ってから始めれば、フルタイムで８年から１２年でしょうか（音楽なんかやってる人は早いみたいですよ。あと話し好きの方）？
英語は確かに必要なんですが、習得に必要とされるリソースの量に対して、リターンが微妙なのは事実です。私は勉強しなかった方ですが、それでも「今まで英語に使ったリソースを全て他の分野に投資出来ていたら、人生ここまで酷く成ってないかなぁ～」と思うことは多々有ります。
一部の人達の間に英語学習を万能薬のように扱う傾向があるようですが、現実に十分な量のリソースを学習に使えない（金銭的、時間的、環境的、或いは精神的理由から）私達の様な人間にとって「英語は勉強しても（自分の英語力が）リターンが発生する閾値に到達しないので、時間とお金の無駄」なんですよね・・・。
子供は６歳前後から[b]ある一定以上の時間、品質の良い英語教育[/b]を施せば、おそらくは違和感なくバイリンガルになるでしょうが、現実には費用と人材の欠如が深刻で、日本でその様な教育を受けられる子供は殆どいません。またそのような教育制度の導入に必要な金額、現在教職についておられる方々の抵抗を考えるに、公立の学校でのサービスの提供は不可能でしょう。
グローバル化に適応するためには英語は確かに絶対必要なんですが、「明らかに習得が（諸々の事情から）出来ないであろう人達に英語学習を勧めるのは国の長期戦略としては正しくでも、短期的には彼らをWORKING POOR ならぬ LEARNING TO BE POORしてしまう可能性は十分あるので、もっと英語学習を勧めるだけではなく、リスクの説明がなされるべきなのかもしれません。
http://anond.hatelabo.jp/20090121152543
（M）イスラム世界との関係では、互いの利益と互いの敬意を基本として共に歩む方法を探す。
（A）イスラム世界に対して、私たちは、共通の利益と相互の尊敬に基づき、新たな道を模索する。
（Y）イスラム世界よ、我々は、相互理解と尊敬に基づき、新しく進む道を模索する。
（M）対立をあおったり、国内の社会問題が生じた責任を西側世界に押しつけようとする指導者たちよ、何を壊すかでなく、何を築けるかで、国民に評価されることを知るべきだ。
（A）紛争の種をまき、自分の社会の問題を西洋のせいにする国々の指導者に対しては、国民は、破壊するものではなく、築き上げるものであなたたちを判断することを知るべきだと言いたい。
（Y）紛争の種をまいたり、自分たちの社会の問題を西洋のせいにしたりする世界各地の指導者よ、国民は、あなた方が何を築けるかで判断するのであって、何を破壊するかで判断するのではないことを知るべきだ。
（M）腐敗、策略、口封じで権力にしがみつく指導者たちは、大きな歴史の過ちを犯していることを知るべきだ。
（A）腐敗と謀略、反対者の抑圧によって権力にしがみついている者たちは、歴史の誤った側にいることに気づくべきだ。
（Y）腐敗や欺き、さらには異議を唱える人を黙らせることで、権力にしがみつく者よ、あなたたちは、歴史の誤った側にいる。
（M）しかし、その握りこぶしをほどくならば、我々も手を差し伸べる。
（A）そして、握りしめたそのこぶしを開くのなら、私たちが手をさしのべることを知るべきだ。
（Y）握ったこぶしを開くなら、我々は手をさしのべよう。
（M）貧しい国々の人々には、我々が一緒に汗を流すことを約束する。農地が豊かになり、きれいな水が流れるようにし、空腹を満たすとともに、飢えた心も満たす。
（A）貧しい国の人々に対しては、農場を豊かにし、清潔な水が流れるようにし、飢えた体と心をいやすためにあなた方とともに働くことを約束する。
（Y）貧しい国の人々よ、我々は誓う。農場に作物が実り、きれいな水が流れ、飢えた体に栄養を与え、乾いた心を満たすため、ともに取り組むことを。
（M）そして我々のように比較的豊かな国々は、国外での苦しみに無関心でいたり、影響を気にとめずに、地球の資源を浪費はできない。
（A）そして、米国同様に比較的豊かな国には、私たちはもはや国外の苦難に無関心でいることは許されないし、また影響を考えずに世界の資源を消費することも許されない、と言わなければならない。
（Y）我々と同じように比較的満たされた国々よ、我々が国境の向こう側の苦悩にもはや無関心でなく、影響を考慮せず世界の資源を消費することもないと言おう。
（M）世界は既に変革しており、我々もそれに合わせて変わらなければならない。
（A）世界が変わったのだから、それに伴って私たちも変わらなければならない。
（Y）世界は変わった。だから、我々も世界と共に変わらなければならない。
（M）我々は進む道を熟慮しながらも、今まさに、遠く離れた砂漠や山々で警戒に当たる勇敢なアメリカ人たちへ謙虚に、そして感謝の念を持ち、思いをはせる。
（A）私たちの目の前に伸びる道を考えるとき、つつましい感謝の気持ちとともに、いまこの瞬間にもはるかな砂漠や山々をパトロールしている勇敢な米軍人たちのことを思い起こす。
（Y）我々の前に広がる道について考える時、今この瞬間にもはるかかなたの砂漠や遠くの山々をパトロールしている勇敢な米国人たちに、心からの感謝をもって思いをはせる。
（M）彼らは今日、我々に教訓を与えてくれる。アーリントン国立墓地に眠る英雄たちと同じように。
（A）アーリントン国立墓地に眠る戦死した英雄たちの、時代を超えたささやきと同じように、彼らには、私たちに語りたいことがあるはずだ
（Y）彼らは、アーリントン（国立墓地）に横たわる亡くなった英雄たちが、時代を超えてささやくように、我々に語りかけてくる。
（M）彼らが自由の守護者だからだけでなく、彼らは奉仕の精神を体現し、自分たち自身よりも偉大なものが存在し、それに意味を見いだす人たちだからこそ、たたえる。
（A）私たちが彼らに敬意を表するのは、彼らが私たちの自由の守護者だからというだけでなく、彼らが奉仕の精神の体現者、つまり自分自身より大切なものに意味を見いだそうとしているからだ。
（Y）我々は彼らを誇りに思う。それは、彼らが我々の自由を守ってくれているからだけではなく、奉仕の精神、つまり、自分自身よりも大きい何かの中に進んで意味を見いだす意思を体現しているからだ。
（M）そして、この歴史的な瞬間に、まさにこの精神を我々がみな共有しなければいけない。
（A）そして今、一つの時代が形作られようとしている今、私たちすべてが抱かなければならないのがこの精神だ。
（Y）これこそが時代を決するこの時に、我々すべてが持たねばならない精神だ。
（M）政府の能力や義務は、究極的には米国民の信念と決意が決定する。
（A）なぜなら、政府はできること、しなければならないことをするにせよ、この国が依存するのは、究極的には米国人の信頼と決意であるからだ。
（Y）政府はやれること、やらなければならないことをやるが、詰まるところ、わが国がよって立つのは国民の信念と決意である。
（M）それは、堤防が決壊した時に見知らぬ人をも招き入れる親切や、友人が仕事を失うことになるよりも、自分の労働時間を削ってでも仕事を分け合おうという労働者たちの無私無欲のおかげで、最も暗い時を切り抜けることができる。
（A）最も難しい局面を乗り切るのは、堤防が決壊した時に見知らぬ人を招き入れる親切心であり、友人が仕事を失うのを傍観するよりは自分の就業時間を削減する労働者の無私の心だ。
（Y）堤防が決壊した時、見知らぬ人をも助ける親切心であり、暗黒の時に友人が職を失うのを傍観するより、自らの労働時間を削る無私の心である。
（M）煙に満ちた階段を駆け上がる消防士の勇気や、子どもを育てる親たちの意志が、最終的に我々の運命を決定付ける。
（A）煙が充満した階段に突っ込んでいく消防士の勇気、子どもを育てる親の献身の気持ちが、私たちの運命を最終的に決める。
