Visiting Fukushima City (June 1, 2011)

1. Introduction
On Wednesday, June 1, 2001,  I visited Nakate-san, the representative of “Fukushima Network for Saving Children from Radiation”, in Fukushima City to hand two Geiger counters (International Medcom CRM-100 and Inspector Alert) provided by Safecast. This article is about the trip.
2. On Shinkansen
I went to Fukushima by Shinkansen “Tsubasa” from Tokyo. I occasionally measured the radiation level inside the train car. At Utsunomiya Station while the train was stopped, I saw 0.12 micro Sv/h, but when approaching Koriyama, I saw 0.42 micro Sv/h, and at Koriyama Station while the train was stopped, I saw 0.56 micro Sv/h. Between Koriyama and Fukushima, it was 0.51 micro Sv/h.
Discovering that I could measure high radiation level even on board train that was running, I decided to measure more frequently on train on my way back. After I mapped the result of monitoring radiation levels in juvenile welfare institutions in Fukushima by the prefecture ( ), I could infer that the areas with higher radiation levels than the lower limit of what we call radiation control area by Japanese laws have spread across the prefectural boarders, but since we do not have (or I thought we did not have) the similar data outside Fukushima Prefecture, I could not be certain of the extent. I figured that by measuring radiation levels while going south by Shinkansen, I could have a better understanding of the extent to which the radioactivities have spread (the result is shown in 5, Conclusions).
In Fukushima City, I have witnessed a number of surprising facts. The first surprise was that people wore normal clothes when they got off at Fukushima Station. Most of them did not wear facial masks. I was even more surprised to see a man with T-shirt and short pants. I wore a facial mask, a cap, a long-sleeve and smooth wearing so as to prevent radioactive materials to stick.
On the Shinkansen platform of Fukushima Station, I saw 0.58 micro Sv/h even though the platform is at a high location.
3. Measuring on Foot
I was a bit startled to detect a level of radiation comparable with those in radiation control areas, but after starting walking around the city, that sense soon got benumbed, because there was nowhere in the city, at least as far as I walked, where the radiation level was below 0.6 micro Sv/h (which approximates the level for radiation control areas defined by Japanese laws).
The temperature was a little lower than around Tokyo in Fukushima City, but I got soon accustomed with the chilliness. The rain began to fall, and I bought an umbrella at Seven-Eleven near the station. But most people I saw in the city, either walking or riding bicycles, did not use umbrellas or wear facial masks.
I found a group of people, probably college students and their lecturer, moving with heavy weights and goggles. One of them was on a wheelchair. It was perhaps a class to experience the daily life of elderly people. In fact, people in Fukushima City in many respect were spending their daily lives, whether they liked it or not.
At a bus stop on the side of an elementary-school ground, I saw 2.36 micro Sv/h on my Geiger counter. Luckily, at least on that day, no one was in the ground. Usually, I publish my reading on radiation photo map calculated from an average of counts in about 90 seconds. But since precision of lower digits is not that meaningful with this large value, and because each detection of radiation consumes power, I decided that about 30 seconds should be OK.

In front of a gate of a high shool. 2.31 micro Sv/h on average of 32 seconds.
In front of a gate of a high school. 2.31 micro Sv/h on average of 32 seconds.

I saw 2.31 micro Sv/h at the flower garden in front of the gate of a high school. Soil without any efforts of maintenance, I think, tends to make radioactivity stay, and vegetables do absorb radioactivity. Which, I imagine, makes flower gardens and plantings sources of higher radiation levels. But concrete surfaces may also tend to stick fast to radioactive materials, according to findings by Safecast and other measurements.
One of the most surprising events in my trip was that a high school girl was reading something looked like a textbook sitting on a bench near the school without any sort of protection from radiation or the rain. Since I saw the reading on the Geiger counter, it looked to me as if she was there with some sort of tragic resolution. But perhaps the truth was that she simply did not know. After I told her that the place had high level of radiation, she left. (It could be because she thought that she was talked to by a strange middle-aged man.)
On a road facing an elementary school. 1.62 micro Sv/h on average of 34 seconds.
On a road facing an elementary school. 1.62 micro Sv/h on average of 34 seconds. School boys were wearing short pants under the rain.

Near the location, there is an elementary school that is attached to a university. The school boys on their way home were playing, wearing short pants. There could be less radioactive materials in the air because of the rain. But it was certain that they were on the ground. I did not know what to do watching children walking and running with their legs exposed while the radiation level in the air was 1.62 micro Sv/h at that time.
I continued my measurements especially near schools I found on the map in my iPhone, walking down south and crossing a bridge. I was heading at NPO IL Center Fukushima where Nakate-san work.
Flowers on the road side. 2.91 micro Sv/h on average of 31 seconds.
Flowers on the road side. 2.91 micro Sv/h on average of 31 seconds. About 1m high from the ground.

The photograph on left is one I took on my way back after meeting Nakate-san. I saw 2.91 micro Sv/h, which was the highest record in the trip. It was measured at 1m high from the ground, suggesting that even higher values could be measured at lower height, and probably across Fukushima City.
I wrapped my Monitor 4 with vinyl in order to protect the counter from dusts, which turned out to be a good protection from the rain, which suggests that there was no influence of alpha. But some beta may have influenced the readings. If you are concerned, please think in terms of CPM instead of Sv/h. Since Monitor 4 is calibrated to gamma rays from Cesium 137 so that 100CPM nearly equals 1 micro Sv/h (with error of plus-minus 15%), you can figure that, for example, 2.91 micro Sv/h means 291CPM or so. Imagine that this means 4.85 counts per second. Still, the Geiger tube of Monitor 4 is not so sensitive.
At the side of the school ground of a high school. 1.62 micro Sv/h on average of 38 seconds.
At the side of the school ground of a high school. 1.62 micro Sv/h on average of 38 seconds. The baseball club was continuing their practices under the rain.

The photograph on right has been the most controversial among the ones I have published in the album of “Save Children of Fukushima” Facebook page. I saw 1.62 micro Sv/h at the side of a high school ground, where the baseball club was practicing in the rain (the radiation level could be higher on the ground itself). I felt as if something was breaking in my mind when I saw this.
What can we do? I think that what we adults can do is to let those high school students play baseball they love as long as they want in a safe, distant place. The next question is how we can achieve it and what each of us can do to assist that.
A map has been generated to plot the measurements I took on foot ( viewable from ) as shown below.
Radiation Photo Map of Fukushima CIty (June 1, 2011, measured on foot)
Radiation Photo Map of Fukushima City (June 1, 2011, measured on foot)

The red marble indicates where the radiation levels were especially high, being equal to 2.0 micro Sv/h or higher. Although nothing definitive can be said with this small number of samples, the distribution of red marbles seems to have some geographical characteristics. So I made it to show terrains as well.
Radiation Photo Map of Fukushima CIty (June 1, 2011, measured on foot, with terrain)
Radiation Photo Map of Fukushima CIty (June 1, 2011, measured on foot, with terrain)

This is nothing more than a hunch, but hot spots may spread on the foot of mountains (of course, the whole Fukushima City is a hot spot, but those hot spots are where special attentions are required). Perhaps we should check the foot of mountains next time.
4. Talking with Nakate-san
I met Nakate-san, the representative of “Fukushima Network for Saving Children from Radiation”, at NPO IL Center Fukushima.
Nakate-san with an Inspector Alert in his hands.
Nakate-san with an Inspector Alert in his hands.

Nakate-san seemed happy to receive an Inspector Alert, a handheld surface contamination meter. He told me that “Fukushima Network for Saving Children from Radiation” has already had some of these units, but certainly would like to use more of them. When I told him that Safecast would be happy to hand more sensors if people would share the measurements with public, he told me that he liked the idea of encouraging people to measure radiation to help others receiving sensors, because that would fit the current trend in Fukushima for mutual aids.
In Fukushima City, Nakate-san told me, radiation levels higher than 0.6 micro Sv/h can be observed even inside houses, if, for example, the house is wooden. Lots of people want Geiger counters to decide whether they should evacuate their houses by measuring the surrounding radiation levels. I felt once again that it is urgent to deliver as many sensors as possible in such an area.
Nakate-san tells the beginning of Fukushima Network for Saving Children from Radiation.

Nakate-san cited someone’s saying “It’s not only fuel rods that have been exposed by the nuclear power plant accident. The problems and virtues we have had in Japan have also been exposed.” Describing the activities of “Fukushima Network for Saving Children from Radiation”, he said he did not want to easily use the words like “bonds”, but he admitted that it had been goodness in people’s minds and bonds among them, which have been exposed as actions
“People have always been willing to protect their children. But did not act that way from time to time, while they were living ordinary lives,” said Nakate-san. “But they have changed themselves through the incident. They have made actions.”
He told me that Fukushima people have had this tendency to be tolerant, especially in Naka-dori, part of Fukushima Prefecture where Fukushima City and Koriyama City are situated. They had avoided fighting over “trivial” problems… “But this time, it was different,” he said. “They have suddenly started to act and to speak at once. They are now eager to cooperate and to do things together.”
He told me that activities of “Fukushima Network for Saving Children” are region-based. They are helping people to evacuate, to clean up radioactive materials and to measure radiation levels. He emphasized that knowledge is important to protect our children. Therefore sharing knowledge is also an important part of the activities of the network. Currently, the network is using a room in Nakate-san’s house as the office, which was dedicated to his children who are now living with his wife in the west of Japan.
“What makes the situation different from Chernobyl,” Nakate-san said, “is first of all the Internet. Through the Internet, we can access information. We can read articles of foreign media such as New York Times. No one can hide information any longer. Secondly, the NPO activities, which have risen after Hanshin-Awaji Earthquake. Those have empowered us to do this kind of activities.”
I thanked Nakate-san, being a researcher of the Internet for a long time.
5. Conclusions
Roadside Tree. 1.57 micro Sv/h on average of 34 seconds.
Roadside Tree. 1.57 micro Sv/h on average of 34 seconds.

On my way back to the station, I passed many people on their way home from work or children going to “juku” (exam-preparation schools), which looked like an ordinary scene at dusk in Japan. Without knowing about the radiation levels here, no one would think that this place has a too big problem to live. Of course, there are people evacuating or helping others to evacuate such as “Fukushima Network for Saving Children”. But what about the rest of them? How do they feel to be there?
This was a too short stay to suppose what were going on their hearts.
In the Shinkansen on my way back to Tokyo, I continuously measured the radiation levels inside the train in order to have a general idea of the southern extent of high radiation areas that include most of Naka-dori district. Below is the resulted map (viewable from ).
Radiation Photo Map of Tohoku Shinkansen (June 1, 2011, measured on board)
Radiation Photo Map of Tohoku Shinkansen (June 1, 2011, measured on board)

This is just an approximation, as the measurements were taken while the train was rapidly moving, suggesting that each marble represents gamma rays from a wide area, and the counts drastically decreased inside tunnels (the fact that radiation level decreased inside tunnels suggests that the source of radiation was outside, not inside of the train).
This is nothing but a guess, but the high radiation area seemed to extend as far as Okawara City, Tochigi Prefecture, southward (later, this was confirmed by the map created by Prof. Hayakawa of Gunma University).
6. Later in Fukushima City…
The two Geiger counters Safecast provided were put into the test run just two days later. I do not know if they have been successful in sharing and publicizing the sensor readings, but if they have not, I think that we have to question once again, as a design problem, how we can make it easier to share and publicize sensor readings for those people worried daily by radiations and occupied with their struggles of providing safer places for their children or evacuating from where they live.
Day after day, questions have been posted at the mailing list of “Fukushima Network for Saving Children” with respect to the means and conditions for evacuation. Just the other day, consultation on children’s health was provided by a group of doctors visiting Fukushima City. However, those high school students who have been spending their after school outdoors practicing their athletic skills were not present.
Talking about high school students, yet another issue has risen in Fukushima. “Fukushima So-Bun”, the 35th All Japan High School Cultural Festival, which had been investigated whether it was appropriate to be held after the earthquake and nuclear power plant accident, was decided to be held in locations both inside and outside the prefecture for five days from August 3. The venues include those high radiation areas such as Fukushima and Koriyama cities. In this event, more than 6,000 high school students all around Japan will gather in Fukushima Prefecture. I feel as if our knowledge and preparedness are tried in the question whether we can protect the safety of those high school students visiting Fukushima while both aftershocks of the earthquake and the nuclear power plant accident are far from being close to conclusions today.

1. はじめに

2011年6月1日(水)、Safecast から託された 2台のガイガーカウンタ (International Medcom 社 CRM-100 および Inspector Alert) を持って、「子どもたちを放射能から守る福島ネットワーク」の代表を務めていらっしゃる中手さんにお会いするために、福島市を訪ねました。この記事は、その記録です。

2. 新幹線にて

東京から新幹線「つばさ」で福島を目指しながら、参考までにと思い、たまに車内の放射線レベルを測定しました。宇都宮駅 (停車中) では 0.12μSv/h だった放射線レベルが、郡山に近づくと 0.42μSv/h になり、郡山駅 (停車中) では 0.56μSv/h を記録しました。郡山-福島間では 0.51μSv/h でした。

車内で、走行中にも関わらず高い放射線を検出できることが分かったので、帰りには、より細かに測定を行うことにしました。福島県による児童福祉施設等の放射線モニタリング調査結果をマップした際 ( )、県境を越えて放射線管理区域レベル以上の場所が広がっていることは推定できたのですが、福島県外には同様のデータが無いので、どこまで広がっているのか、その境界が分かりません (とそのときは思っていましたが、データはあったようです)。新幹線で南下しながら測定を行うことで、その境界がどこにあるか、当たりが付けられると考えたのです (結果は下の「5. まとめ」に書いています)。


福島駅の新幹線プラットフォームでは、高所にも関わらず 0.58μSv/h が観測されました。

3. 徒歩での放射線測定


いきなり放射線管理区域レベル (3ヶ月で 1.3mSv) 相当の放射線を検出し、いささかうろたえましたが、そんな感覚は、市内を歩き始めて、すぐに麻痺することになります。私が歩いた範囲では、市内で 0.6μSv/h を切ることは無かったからです。




小学校のグラウンドの脇にあるバス亭で雨宿りがてら測定したところ、2.36μSv/h が出ていました。幸いなことに、その小学校では、少なくともその日は、屋外での活動は行われていないようでした。通常、私は、放射線フォトマップ等で測定値を公開する際、約90秒カウントした平均をとっていますが、これだけの大きさの値が出ている場合、細かな桁での正確さにはさほど意味がありませんし、ガイガーカウンタの電池の消耗も考えて 30秒程度で十分とすることにしました。


ある高校の校門の前の花壇では、2.31μSv/h を観測しました。土があって、何の処置も行われていない場合は、放射性物質が溜まりやすいと思いますし、植物にも取り込まれると思います。ですので、花壇や植え込みがある場所では、放射線レベルは高めになると想像しています。かといって、コンクリートの表面にも、放射性物質がこびりつく傾向がありそうなことが、Safecast やその他の測定により、分かってきているようです。

今回、特に驚いたことのひとつは、この高校のそばのベンチに腰掛けて、女子学生が、雨の中、傘も何も使わずに、教科書のようなものを読んでいたことです。私は、ガイガーカウンタの表示を見ていたので、彼女が何かの悲壮な覚悟をもって、そこにいるかのような、ただならぬものを感じたのですが、本人は、単に知らなかっただけかも知れません。高い放射線が出ていることを告げると、そこから居なくなりました (変なおじさんに声をかけられたと思ったのかも知れません)。


近くには大学の付属の小学校があり、そこの男子生徒たちが、半ズボン姿で、仲間たちと戯れていました。雨のため、この日、空気中に放射性物質はあまり舞っていなかったかも知れません。それにしても、地表に放射能があることは明らかでしょう。路上で 1.62μSv/h が観測されている中、こどもが素足を出して歩いている、走っている、ということに対し、どうしたらよいのか、私には分からず、途方に暮れました。

その後、主に学校のある場所を iPhone のマップで探して測定を続けながら、橋を渡って南にある NPO 法人 IL センター福島へと向かっていきました。

道端の花壇。31秒間の平均で2.91μSv/h。高さは地表から 1m ほど。

左の写真は、中手さんにお会いした後の、帰り道に撮ったものです。今回の測定では最大値となる、2.91μSv/h を観測しました。約 1m の高さで測ったものですが、もちろん、もっと低い位置で測れば、もっと大きな値が、福島市の至るところで観測できたと思います。

今回は、塵よけのため、というか結果的には雨よけのために、Monitor 4 にビニール袋を被せて測定をしていたので、α線の影響は無いと思います。ですが β線はそれなりに拾っていると思うので、気になる方は、CPM で考えて頂ければよいと思います。Monitor 4 はセシウム137 のγ線に対して 100CPM ≒ 1μSv/h になるように校正されています (誤差 ±15%) ので、例えば 2.91μSv/h なら、Monitor 4 で 291CPM くらい出ていた、とお考えいただければよいと思います。1秒当たり 4.85 回、カウント音が鳴ることを想像して頂けると、すごさが分かると思いますし、Monitor 4 のガイガー管は、それでも感度が低い部類に入ります。


右の写真は、今回、「福島のこどもたちを守ろう」Facebook ページのアルバムで公開した中でも、最も議論を呼んだ写真です。高校のグラウンドで、雨の中、1.62μSv/h が観測される中 (グラウンドの脇で測ったもので、グラウンド上ではもっと出ている可能性があります)、野球部が練習をしていました。それを見たとき、頭の中が張り裂けそうな感じがしました。


今回、徒歩で測定した結果を地図上にマップしたところ、下のようになりました (このマップは から見られます)。

福島市の放射線フォトマップ (2011年6月1日徒歩での測定分)

赤い丸は、特に放射線レベルが高く、2.0μSv/h 以上の場所を示します。これだけの少ないデータでは、何が言えるわけでもないのですが、ぱっと見た感じで、赤い丸の分布に地理的な特徴があるようにも見えたので、次のように、地形を表示させてみました。

福島市の放射線フォトマップ (2011年6月1日徒歩での測定分、地形を表示)

もちろん、このような少数のデータでは何も確定的には言えませんが、山際にホットスポットが生まれている可能性があると思います (福島市全体がホットスポットであることに間違いないのですが、その中でも、特に注意を要する場所という意味です)。今後は、山際の部分を特に測定して確かめるべきかも知れません。

4. 中手さんとのお話

NPO 法人 IL センター福島にて、「子どもたちを放射能から守る福島ネットワーク」代表の中手さんとお会いしました。

Inspector Alert を手にする中手さん

早速、2台のガイガーカウンタをお渡しすると、中手さんは笑顔で受け取ってくださいました。すでに、Inspector Alert を含む多くのガイガーカウンタを寄付にて取得されているそうですが、Safecast から今後も継続的に測定器が提供されることを期待してくださっているようです。

Safecast では、一般の方々からのデータの投稿を受け付け、マップ上に共有・公開していますが、そうした活動に、「子どもたちを放射能から守る福島ネットワーク」のみなさんの出来る範囲でこ協力いただけると、より多くのガイガーカウンタをお渡しできることに繋がるのではないでしょうか、というお話をさせていただいたところ、「自分たちが測定することで、他の人々もガイガーカウンタを持てるようになる」という考えは、相互扶助の気持ちが特に盛り上がっている今、効果的に働くのではないか、と仰ってくださいました。

福島市では、木造家屋などの場合、屋内でも 0.6μSv/h を超える場所もあるそうです。多くの方々が、自分の身の回りの放射線量を測り、避難すべきかどうかの判断の参考にするために、ガイガーカウンタの使用を希望していらっしゃるそうです。こうした地域に、多くの測定器を届けることは、急務であると改めて感じました。






「チェルノブイリの時と、なんといっても違うのは、インターネットの存在」と、中手さんは言います。誰もが情報へのアクセスを持ち、ニューヨークタイムズといった海外メディアの記事さえも読めるのですから、もはや、情報を隠蔽し続けることは、誰にもできません。また、阪神淡路大震災後から活発になった NPO の活動も大きいといいます。これらふたつが、状況を別なものにしており、そこから希望が生まれるといったお話を、中手さんはしてくださいました。


5. まとめ




帰りの新幹線では、放射線レベルが高い場所がどこまで南に延びているか、おおよその当たりをつけるために、走行中の車内で継続的に測定をしてみました。その結果のマップが下のものになります (このマップは から見られます)。

東北新幹線の放射線フォトマップ (2011年6月1日乗車分) 走行中に測っているため、参考程度の測定ではあります

そもそも、高速で走行中であり、広範囲の場所からのγ線を拾っているだろうこと、トンネル内ではカウントが激減することなどから、正確なデータでは全くありませんが、傾向は見て取れると思います (トンネル内で放射線レベルが下がることは、車内ではなく外部に放射線源があることを示していると思います)。

この結果から、私は、放射線濃度が特に高い場所が、南の方では栃木県大田原市くらいまで延びているのではないか、という感触を得ました (このことは、群馬大学の早川教授により作成された等値線マップにより後に確かめられました)。

6. 後日談

Safecast からの2台のガイガーカウンタは、この 2日後にはテスト運用に回されたといいます。測定値の共有・公開がうまくできているかは分かりませんが、うまくいっていないとしたら、どうしたら、現地で放射能に悩み、こどもたちのために安全な環境を用意したり、安全な場所に避難したいと、そればかり考えている人々にとって、測定値の共有や公開に参加することが容易になるか、改めてシステムの設計上の問いとして考えてみる必要があると思います。


高校生といえば、またひとつ、新たな問題が出てきました。震災や原子力発電所の事故を受け、開催が再検討されていた、「ふくしま総文-第35回全国高等学校総合文化祭-」( ) が福島県内外の各会場で 8月3日から5日間、開催されるといいます。会場の中には、高い放射線が観測されている福島市や郡山市も含まれています。全国から6,000人を越す高校生たちが、福島県に集まるとのことですが、余震も、原子力発電所の事故も、収束に向かっているとは言い難い中、訪れる高校生たちの安全を守ることが果たしてできるのか、私たち大人の見識と覚悟が改めて問われているように感じます。