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PROJECT

University Student Union Network
International School Network

In writing this book, I started and run Intlschool in June 2006 with my two daughters and my wife. In order to think about world peace, my mission is to interview ambassadors to Japan, interview UN agencies, and publish articles on the website and newspapers. During the interview, I found that improving the literacy rate in emerging countries would be a clue to eliminate poverty. We called on ambassadors to Japan and people from UN agencies to raise the literacy rate. A pdf booklet showing the contents is posted on the website. It is a program that teaches children in developed countries to read and write directly to children in emerging countries.
I thought that it would lead to world peace if children who are not yet very particular about race, ethnicity, religion 7, tradition, and culture come into direct contact with each other and become friends. And I think that if we educate children in emerging countries and get them to work in better conditions, not only their own lives but also society will be stable. However, inequality at the national level cannot be resolved by literacy rates. It is meaningless unless every country has a stable environment where people can live other lives and has the same standard of living as the world. Currently, IT is sweeping the world and SNS is driving the world economy. The scholarship that forms the basis of this is physical electricity. Therefore, I made a book that can be learned in an easy-to-understand manner to help students who are interested in electricity, and completed it in December 2020. 
We hope that this book will help students in emerging countries. And I hope that it will be useful for adults who are already working. Life expectancy at this point is said to be one year. I would like to use the remaining time to reach those who need this book. This book is sold in Japanese Yen for 800 Yen. In the case of US dollars, it will be sold for 7 dollars. There will be a separate shipping cost. To apply, please email Intlschoolnet.

 仁科研(横浜の焼却灰埋め立て) 2011年9月11日

こんにちは

今回の横浜の焼却灰埋め立てで不安を取り除くために基本的なことから簡単に分かりやすく説明いたします。

ご存じのように水力発電所は水、火力発電所はオイルで発電します。

原子力発電所はウランを燃料に発電をしているのです。

ウランという大きな原子に人工的に中性子というものをぶつけ、ウランを壊します。(核分裂)このウランが壊れ新しい複数の原子に分かれたとき膨大な熱エネルギーと放射線を出します。この熱で水を蒸気にかえ発電機を回し電気を得ます。このとき二つに壊れた原子の中にヨウ素131や、セシウム134があります。3月に原子炉建屋の爆発があった際そのヨウ素131やセシウム134が大量に空気中に放出されてしまいました。このヨウ素131やセシウム134は無理やり作られたものなのでとても不安定です。不安定なこれらの原子は自ら壊れ安定な原子になろうとします。このときに放射線や熱を出すのです。この放射線が今問題となっています。しかしこの放射線は水を通り抜けることが苦手です。燃料棒を水の中に入れておく、コンクリートの壁で覆うという理由もそこにあります。(コンクリートには水分が多く含まれています。)

ここで単位の確認をしておきましょう。

放射性物質(ヨウ素131・セシウム134等)が放射線を出す能力を表す単位を「ベクレル(Bq)」放射線による人体への影響度合いを表す単位を「シーベルト(Sv)」、といいます。

もう少し具体的に説明します。

不安定なヨウ素131やセシウム134が1秒間に放射線を何回出しながら安定な方向に壊れていくか数えた数字が「ベクレル(Bq)」です。比較しやすくするために測る物の重さを1kgに統一しています。たとえば「焼却灰が6400ベクレル」とは灰1kgから1秒間に出てくる放射線の数が6400と言うことです。

この放射線が我々生物に与えるダメージを、シーベルト[Sv]という単位で表しています。「ベクレル(Bq)」にある数字を掛けるとシーベルト[Sv]になります。ある数字のことを係数(放射線荷重係数)と呼んでいます。

なぜヨウ素131とセシウム134が問題になるのでしょうか。

ウランが壊れたとき他の原子になる確率よりもセシウム134やヨウ素131になる確率が高いということ、また体内に入りやすいということが問題です。体内には口から食べ物として入る経口摂取と呼吸により体内に取り込まれる吸入摂取があります。

放射線はいつまで出続けるのでしょうか。

ヨウ素131の半減期は8日です。8日でヨウ素131の半分の原子が放射線(ガンマ線)を出しながら安定なキセノンという別の物質に変わります。更に8日でその半分と減っていきます。その繰り返しでどんどん減っていきます。原子炉建屋の爆発が180日前ですからヨウ素131はほとんどなくなってしまいます。安定なセシウムに比べ勢いよくヨウ素そのものが存在しなくなります。その意味では今回の横浜に来る焼却灰にヨウ素131が含まれているという心配はありません。

原子炉建屋の爆発が起きた当時は事情が異なりヨウ素131が心配でした。

ヨウ素131は、水や食べ物を通し体内へ(経口摂取)、同時に空気中から呼吸により吸入摂取されてしまいます。ヨウ素そのものは、人体に必要な元素で、甲状腺に蓄積される性質があります。ヨウ素131も摂取されると、甲状腺に集まり、そこで局所被曝を起こします。半減期が8日と短いことは摂取してしまうと勢いよく放射線を出し内部被曝してしまうということです。特に、子どもは細胞分裂が盛んに行われているので、DNAに障害が発生するとその影響も早く出てしまいます。(細胞分裂をする際、二重らせん遺伝子がほぐれダメージを受けやすい構造となります。広島の原爆のとき細胞分裂が盛んな頭髪が抜けた理由はここにあります。)

セシウム134の半減期は2.06年です。ヨウ素131に比べるとゆっくりと安定した物質に変わっていくことが分かります。原子炉建屋の爆発から半年が経過していますので1割から2割は安定な物質に変わっています。しかし8割以上のセシウム134が残っています。セシウム134は気体となり風によって運ばれ吸入摂取されてしまいます。主に筋肉、骨に蓄積されます。今回の焼却灰埋め立ての議論の焦点はこのセシウム134の安全性にかかっています。

さて

横浜焼の焼却灰は観測時の最大値を撮り6400ベクレル(実際にはこれより小さい値です)としています。しかし原子炉建屋の爆発から半年が経過していますので概ね5000ベクレル/㎏に減っています。

半減期が約2年、半年経っているということは概ね25%分の年月が過ぎた計算です。

セシウム134のベクレルをシーベルトになおす吸入係数は、1億分の2(シーベルト/ベクレル)です。

したがって5100×1/10×2.0/100000000 = 0.00001シーベルト/kg = 10 マイクロシーベルト/㎏

1㎏の焼却灰をすべて吸い込んだ場合10マイクロシーベルトの放射線被ばくになります。現実には灰を1g吸い込むこともできませんが仮に1g吸入摂取すると1/1000の00.1マイクロシーベルトになります。

1年間では365日×24時間分の8760倍、すなわち年間0.0876ミリシーベルトとなります。

IAEAの厳しい基準(年間1ミリシーベルト以内)もクリアしています。

尚、原発事故以前に日常生活で自然界より受けていた放射線量は年間約2.5ミリシーベルトでした。

私は今回の焼却灰埋め立てに関し何の科学的問題もないと思います。焼却灰の処理について福島県をはじめとする東北の方々にすべて負担して頂くのではなく、横浜市民も東京電力から電気を利用している享受者としてその責任の一端を負うべきであると考えます。

いずれにしても放射性物質(ヨウ素131・セシウム134等)は時間とともに安定な物質に変わり放射線を出さなくなります。化学物質の汚染(例えば、水銀・鉛・クロムなど)と異なり食物連鎖により蓄積濃縮されることはありません。時がたてば魚も野菜も安心して食せるようになります。

仁科雅之

 

I am here to explain to you all the questions you have in mind, about all you need to know, in an easy and understandable language about the ash burial in Yokohama. As you know, in hydroelectricity we use water, and in heat energy we use oil.

In nuclear energy, we use uranium.

Uranium is a big atom that if you artificially put a Neutron, then breaks up the uranium. And as the uranium breaks into lots of new atoms, they produce huge heat energy and radiation. From this heat, the water changes into vapor and the vapor moves the generator and the generator produces electricity.

Inside the broken uranium atom, there are iodine 131 and cesium 134, etc. In March, when the nuclear power plant exploded, the iodine 131 and cesium 134 were radiated into the air.

Iodine 131 and cesium 134 are made artificially, so they are unstable. These unstable atoms try to break into something, to become stable. So what they do is, give out radiation and heat. This radiation is what has now, created very a troublesome deal. That radiation, however, cannot go through water very well. It is why concrete, having a fuel rod inside it, was used to make the walls. (Concrete has lots of water in it.)

Making sure of the measurements

The number of radioactive substances (iodine 131 and cesium 134) is measured by becquerel (Bq) and the amount of damage and affection to people from the radiation is measured by sievert (Sv).

Here is a more detailed explanation.

The amount of iodine 131 and cesium 134 break up (to become stable) per second is measured, becquerel (Bq). To make it easy to compare, we say the item's weight is 1 kg. So for example, if the radioactive substance is 6400 becquerel, then that means that 1kg of burned ash gives out 6400 radiation per 1 second.

We measure the damage from the radiation affecting us, people, and animals, sievert (Sv). When multiplying the amount of becquerel (Bq) by a certain number, you can get the amount of sievert (Sv). We call that certain number, Radiation Weighting Factor.

Why are iodine 131 and cesium 134 such a big problem?

When uranium breaks up to become a stable atom, there is a high percentage of it becoming to be iodine 131 and cesium 134 instead of a different atom. And iodine 131 and cesium 134 are easy to get into your body. They can get into your body when you eat through your mouth and when you breathe and inhale.

When will the radiation continue?

Half of all the iodine131 will finish in 8 days. So in those 8 days, half of the iodine131 will become a safety substance called xenon as it gives out gamma rays. And by the next 8 more days, half of what is left will lessen. They will lessen by half every 8 days and so then about 180 days after the plant exploded, iodine131 will be almost completely gone. So this means that there will be no worries that there are any iodine131 in the burned ash that has arrived in Yokohama.

So as the power plant exploded, iodine 131 was a problem, but now, it is not a problem anymore, so there is no need to worry.

Iodine131 can get into your body from what you eat and drink, and (not anymore, only soon after the explosion), from the air. Iodine itself is something the human body requires to take in, and it accumulated in the thyroid gland. But if you take in iodine131, then it will concentrate onto the thyroid gland and local exposure will occur. When you take in iodine131 before 8 days have passed after the plant had exploded, then you will rapidly intake radiation and you will have internal exposure. Small children especially can get worse damage because they have more cell division than adults, meaning that they can damage their DNA much faster. (The double helix structure of the DNA gets loose when the cell divides. It is the reason why people’s hair (a part of prosperous cell division) in Hiroshima came out when the atomic bomb exploded in Hiroshima.)

Cesium 134 will lessen by half in 2.06 years. Cesium 134 changes (to become more stable) much slower than iodine131. It has been about half a year after the explosion, so about 10 to 20 percent of the cesium 134 has been changed into a safety substance, so about 80 percent of the cesium 134 is still left. Cesium 134 becomes liquid as it goes into the winds and it gets into your body by breathing. It gets into your muscles and your bones. This time’s ash burial’s worries are due to the safety of the cesium 134.

So, the ash burial in Yokohama (during March) is 6400-becquerel maximum. Its number is much smaller, so we are overestimating. Half a year had passed so the number had lessened to about 5000becquerel.

The possibility of taking in the cesium 134 is about two in one hundred million. So if we calculate it to this time’s burial, then it will be 5100×1/10×2.0/100000000 = 0.00001sievert/kg = 10 microsievert/kg. If you suppose you breathed in the whole 1kg of the ash, you will exposure 10 microsievert radiation. In real life, you wouldn’t be able to breathe in 1 gram, but if you did, then it would be one out of one thousand so you will exposure 00.1micro sievert radiation.

A year has 365 days × 24 hours so it is 8760 times larger, so in one year you will take in 0.0876 millisieverts. According to the Safety Standards of IAEA, the maximum radiation you are allowed to take in per year is one millisievert. Hence, the amount from the ash burial in Yokohama is within the Safety Standards. The amount of radiation before the Fukushima nuclear power plant exploded was 2.5 millisievert.

I, Masayuki Nishina believe that the ash burial in Yokohama creates no troubles scientifically. I also see that it is Yokohama and Tokyo’s responsibility to deal with the ash, for we use electricity from the Tokyo Electric Power Company, and we cannot let Fukushima and the rest of the Tohoku Area down.

September 19, 2011

Masayuki Nishina

Electricity introductory guide

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