セシウム新基準 乳児用区別に誤解と不安

2012/02/24 10:12

Ｉｚａ！ｚａＫ

　厚生労働省が４月から適用を予定している放射性セシウムの新基準値では、新たに「乳児用食品」の基準が設定され、一般食品（１キロ当たり１００ベクレル）の半分の同５０ベクレルとした。厚労省は「子供が放射性物質の影響を受けやすいとされる点に配慮した」と説明する。

• 食品の新基準値案を了承　放射線審、生…
• 【よくわかるニュース解説】食品中のセ…

　これに対し、消費者団体「フード・コミュニケーション・コンパス」事務局長の森田満樹さんは「乳児用食品だけ別に基準を設けることで、『一般食品を子供に食べさせるのは危ない』と思った人もいるのではないか。実際は一般食品の基準でも十分安全に配慮したものなのに、その説明はほとんどなされず、消費者の不安は解消されないままだ」と指摘する。

30/09 Tsunami survivor won't return home near the sea

BY YOICHIRO KODERA STAFF WRITER

2011/09/30

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Toshiko Matsumoto, 65, far right, prays in front of her home in Okuma, Fukushima Prefecture, less than 2 kilometers from the crippled Fukushima No. 1 nuclear plant, on a brief return on Sept. 1. The bodies of her husband, Shuhei, and grandson, Eiji, were discovered near their home in late May. (Hiroshi Kawai)

Wearing protective clothes, caps, masks and gloves, Toshiko Matsumoto looked from her home where cedar trees were swept away in the March 11 tsunami. With little left to block her view, she could now see the sea.

"I don't like looking at the sea from here," Matsumoto, 65, said, and turned her eyes.

A transceiver dangling from her neck announced that an hour had passed since Matsumoto and other residents returned to their homes in Okuma, Fukushima Prefecture, for the first time on Sept. 1. They were forced to evacuate because they lived within a 3-kilometer radius of the Fukushima No. 1 nuclear power plant.

Matsumoto's dosimeter showed radiation levels above 30 microsieverts, the accumulated total of her radiation exposure since she returned to Okuma. She called the minibus that had taken them to the town, even though she still had 40 minutes left in the two-hour visit to collect belongings. She waited patiently for the bus to take her away from Okuma, perhaps for the last time.

Her brief visit to Okuma allowed Matsumoto to try to bring a sense of closure to all the misery she suffered in the aftermath of the March 11 Great East Japan Earthquake, tsunami and nuclear crisis. But it also gave her painful reminders of all she had lost and the current torment she suffers.

After the bus arrived in Okuma, Matsumoto headed to her home, which is uphill and a 10-minute walk from the coast. It was also less than 2 kilometers from the nuclear plant.

She had trouble walking through the knee-high grass and weeds that had grown after the town was abandoned soon after the quake.

When she finally reached the front of her home, she pulled out a bundle of incense sticks and burned them for her husband, Shuhei, 68, and her 4-year-old grandson, Eiji. They were swallowed up by the tsunami when they fled to the garden after the magnitude 9-0 earthquake struck.

Matsumoto only learned in late May that their bodies had been found. At that time, she was taking refuge at a relative's house in Chiba Prefecture. She and her sons could not search for the bodies because the nuclear accident had forced them to stay away from Okuma.

After lighting the incense in front of the house, she gave offerings for the two--a can of sweet coffee for Shuhei, which was his favorite drink, and a red miniature car for Eiji.

"It must have been lonely to be left in a place like this for three months," Matsumoto said, while putting her glove-covered hands together to pray.

She was cleaning up the mess in her house caused by the earthquake when she heard a roar around 3:30 p.m. She raced upstairs and saw a wall of water pour over the cedar trees, the height of a four-story house, that surrounded her home. She called out to Shuhei and Eiji, but received no reply. The tsunami struck the house, throwing broken trees and electricity poles into the first floor.

March 11 was Matsumoto's birthday. Shuhei was the kind of person who would realize it was her birthday usually a couple of days after the date. But on that day, he remembered it correctly and took her out for lunch at a revolving sushi bar. She said it was a real treat for her.

"(You died in the tsunami) because you did something you usually didn't do," she had said to her husband's remains, now in her apartment in Aizuwakamatsu in the prefecture. "But why did you take Eiji with you?"

It was something that kept bothering her.

But in August, Matsumoto learned what actually happened when her sister-in-law asked for details from the Self-Defense Forces member who had discovered the bodies.

The sister-in-law called Matsumoto to inform her that Shuhei was found holding his grandson. Matsumoto burst into tears.

"You tried to protect him to the end," she said to the remains. She felt slightly relieved.

When Matsumoto returned to her home on Sept. 1, she was accompanied by her oldest son, the father of Eiji.

"Fifty-five microsieverts (per hour)," her son, holding a dosimeter, shouted upstairs. "It is impossible to take out clothes (due to high radiation levels)."

When the quake hit, her son was working at the Fukushima No. 1 nuclear power plant. Despite the disappearance of his father and son, he has continued to work on a schedule of four days on and two days off since the nuclear disaster started.

In late August, he told his mother that he was being transferred to a section handling clerical work. He would not tell her why.

Matsumoto wanted to ask her son many things, like how much radiation he had been exposed to at the plant, and if he was getting enough sleep.

But he would never talk about the nuclear disaster. And Matsumoto said she has never seen tears in the eyes of her son, despite the loss of his child and father. He often appeared absent-minded.

He sat silent for a while in front of the remains of his father and son.

"I sometimes get disoriented and cannot tell where I am," he whispered.

Matsumoto did not know what to say to her son.

She followed him upstairs, where she spotted a black leather wrist watch, a gift her two sons and a daughter-in-law had given her on her 60th birthday.

She also found her diary. The last entry was on March 10.

The two items were under collapsed drawers. She hesitated for a bit due to the high radiation readings. But she retrieved them and put them in a plastic bag.

The last item she took from her home was a photo album kept in an upper closet. On the first page of the album was a message: "Be happy ever after." When she turned another page, she found a photo of her and Shuhei on their wedding ceremony.

Before she boarded the bus, Matsumoto looked around at what had become of her home and showed little emotion.

"I will never feel like building a home here again," she said. "I am afraid this is it."

She had never said such things when I interviewed her in late March.

29/09 Ministry sets radiation levels requiring decontamination

BY HARUFUMI MORI STAFF WRITER

2011/09/29

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Workers decontaminate soil with high-pressure water nozzles in Minami-Soma in Fukushima Prefecture. (Asahi Shimbun file photo)

The Environment Ministry will decontaminate areas with an estimated annual dose of 5 millisieverts or more from the accident at the Fukushima No. 1 nuclear plant, which the government will shoulder as its burden in cleaning up the mess.

All the areas recording 5 millisieverts or more are in Fukushima Prefecture and encompass 1,778 square kilometers, or 13 percent of the prefecture's area.

Five millisieverts in an annual dose is equivalent to about 1 microsievert per hour based on the assumption that people spend eight hours outdoors and the rest of the time indoors.

The latest standards are translated into an exposure of about 1 microsievert of radiation per hour.

The cleanup work is aimed at removing soil up to about 5 centimeters down from the ground surface, a point where cesium is concentrated.

The decontamination will also clean up so-called "hot spots" in urban areas where unusually high levels of radioactive substances were measured, such as side ditches and gutters, if the projected annual reading is 1 millisievert or more.

The ministry set decontamination standards for hot spots taking into account the impact on the livelihood of residents in the neighborhood.

As for cleanup of forests, it has decided to remove radioactive materials by scooping up fallen leaves rather than scraping off the topsoil.

The maximum amount of soil, fallen leaves and other debris to be removed under the decontamination plan is set at 29 million cubic meters, the equivalent of 23 Tokyo Domes, according to the ministry's calculation.

But critics said no matter how much the government emphasizes the legitimacy of the latest figure, setting the government standards will be meaningless unless municipalities and residents are convinced of their safety.

Most of the decontamination operations are expected to get under way next year.

The ministry presented results of its estimate for decontamination work to a meeting of experts on Sept. 27.

Hisaki Mori, executive managing director at the Radioactive Waste Management and Nuclear Facility Decomissioning Technology Center and one of the experts sitting in the ministry meeting, called for the government to explain its radiation standards to help ease public concern.

"The government is accountable (for the standards)," Mori said.

The government said in its provisional policy for decontamination released in August that it aims to bring the projected annual dose of radiation to 1 millisievert in the long run.

But the environment ministry decided on the 5 millisieverts a year level for now based on a projection that the cleanup operation would not generate a significant effect in areas with a reading of lower radiation levels even if the work was carried out.

A senior ministry official said the ministry's conclusion was arrived at weighing the pros and cons of cleanup and labor costs against the predicted results.

"It would be ideal to set it at 1 millisievert, but we would not be able to complete decontamination if we insisted on that," the official said.

The ministry expects to eventually bring down radiation exposure levels to 1 millisievert in part as some of the radioactive cesium will have a half-life of two years.

But such cleanup work will not be done in forests.

The environment ministry said instead retrieving fallen leaves and trimming tree branches would suffice, citing a study by the education ministry.

Environment ministry officials said that the removal of leaves and branches would reduce the quantity to be eliminated by one-fifth or one-sixth, compared with the amount of soil that would need to be scraped off in the comparable area.

Another advantage of ridding leaves and branches instead of soil, the ministry said, is to allow officials to further reduce the volume of tainted materials through incineration.

Forests account for about 70 percent of the areas to be covered in the government's decontamination operation.

As for hot spots in urban areas, the government will need to decontaminate about 640 square kilometers in Fukushima and four neighboring prefectures alone.

Officials are expected to use high-pressure water nozzles and other methods to clean up those areas.

About 400,000 cubic meters of soil are expected to be removed as a result.

While the government sets its standards for radiation levels requiring decontamination work, municipalities will likely decide on their own figures.

If they seek to carry out cleanup in areas with radiation levels lower than the government standards, they are required to pick up the tab for the decontamination work.

Meanwhile, the Fukushima city government announced its decontamination plan on Sept. 27, covering all the 110,000 housing units, schools, parks, roads and public facilities in the city.

Its goal is to lower radiation levels in the air to 1 microsievert per hour or lower in all areas where residents live, by the end of fiscal 2012.

It will start the work next month, beginning with areas with a reading of about 3 microsieverts per hour.

09/07 Phát hiện phóng xạ bất thường trong thịt bò Nhật

 09/07/2011 | 17:53:00

Từ khóa : Fukushima, Thịt bò, Phóng xạ, Thịt hộp, Điện hạt hận

Ảnh chỉ có tính minh họa. (Nguồn: Internet)

Theo một thông cáo chính thức từ chính quyền thủ đô Tokyo ngày 9/7, nhà chức trách Nhật Bản đã phát hiện lượng phóng xạ Ceasium cao gấp sáu lần mức cho phép trong thịt bò nuôi tại tỉnh Fukushima, nơi đang phải hứng chịu cuộc khủng hoảng hạt nhân do thảm họa động đất sóng thần hồi tháng Ba gây ra.

Thông cáo trên cho biết, lượng phóng xạ Ceasium được phát hiện trong mẫu thịt của 11 con bò cái được chuyển từ một nông trại ở thành phố Minamisoma, tỉnh Fukushima, gần nhà máy điện hạt nhân Fukushima số 1, tới một nhà máy sản xuất thịt hộp tại thủ đô Tokyo.

Thông cáo nêu rõ mẫu thịt lấy từ 11 con bò này đều cho thấy đã bị nhiễm phóng xạ Ceasium ở mức cao, từ 1.530-3.200 becquerels (Bq)/1kg, vượt xa mức cho phép là 500 Bq/1kg.

Đây là lần đầu tiên chất phóng xạ Ceasium vượt quá mức quy định được phát hiện trong thịt gia súc. Nhà chức trách Nhật Bản cho biết thêm tất cả số thịt bò này đang được lưu giữ trong phòng thí nghiệm và không được phép tung ra thị trường. Tuy nhiên, các nhà chức trách cũng đang rất lo ngại khi có thông tin cho biết, có năm con bò trong đàn bò ở cùng nông trại trên đã được bán ra thị trường Tokyo từ ngày 30/5-30/6.

Ngay sau khi có thông tin khẳng định lượng Ceasium có trong thịt bò, các nhà chức trách chính quyền tỉnh Fukushima đã yêu cầu thành phố Minamisoma kiểm soát chặt chẽ những con bò xuất chuồng, đồng thời kiểm tra mức độ nhiễm xạ trên da của toàn bộ súc vật nuôi tại những khu vực gần nhà máy điện hạt nhân này.

Thành phố Minamisoma nằm ở ngoại ô khu vực nhà máy điện hạt nhân Fukushima, vốn đã bị rò rỉ chất phóng xạ vào môi trường sau vụ động đất và sóng thần hôm 11/3. Số bò nói trên được chuyển tới Tokyo từ một nông trại nằm không xa khu vực cấm vào rộng 20km quanh nhà máy trên./.

(TTXVN/Vietnam+)

26/03 体に影響する被ばく線量の目安

体に影響する被ばく線量の目安（2011年3月26日付夕刊）

Vài phương pháp tìm bài bạn muốn đọc:

Q1. Bạn muốn xem tin tức về tinh trạng phóng xạ tai các nơi?
A: Bạn chọn từ khoá "monitoring" hay "data-colection" tại mục labels

Q2. Bạn muốn đọc các bài của các nhà nghiên cứu, chuyên gia có tính cách hàn lâm (academic)?
A: Bạn chọn từ khoá "Techinical Report" hay "speciallits"

Q3. Bạn muốn xem các bài nhật ký?
A: bạn chọn từ hoá "diary" hay tên tác giả

Q4: Bạn muốn biết về các phóng xạ, tình hinh phóng xạ?
A: Bạn chọn từ khoá "Radiation" "Radiation hazard" "iodin" v.v...

Q5: Bạn muốn tìm xem về các hợp tác quốc tế?
A: Bạn tìm từ khoá "International cooperation" v.v...

Q6: Bạn muốn xem các bài bình luận của các báo, chuyên gia?
A; Bạn tìm từ khoá "editorial"

Chú 1: mục từ khoá với cái tựa là Labels, nằm dưới mục "blog archive", "My Blog List", "my favorit links", để xếp cái bài (rất nhiều) trong "blog archive", bạn click dấu tam giác▼ để dấu ấy thành ► bên đầu list các bài đã post, thì các tin sẽ thu lại ►

Chú 2: về các từ khoá thí dụ ở trên, các bạn có thể tìm thử ngay tại mục labels (từ khóa) trong bài này bên dưới

SCIENTISTS WORK ON ANTI-RADIATION VACCINE

===================================================

SCIENTISTS WORK ON ANTI-RADIATION VACCINE

Nuclear danger in Japan threatens world public, as the world of science celebrates an important innovation.

Russian scientists developed a vaccine protecting against radiation.

The vaccine, developed by joint work of the Russian Academy of Sciences and NASA, proved to be successful on animals which exposed to the radiation level, with which they could live no longer than seven days.

The anti-raditation vaccine made positive effect also on human cells. A Russian researcher in the project said they succeeded even in the situations where the radiation level was ten thousand times higher than normal.

It may take years to complete some necessary testing and the vaccine is not available for clinical use for the time being.

======================================================

HOW MUCH RADIATION IS DANGEROUS?

Here are some facts about radiation and the health dangers it poses:

* Radiation is measured using the unit sievert, which quantifies the amount absorbed by human tissues. One sievert is 1,000 millisieverts and 1 million microsieverts.

* People are constantly exposed to some level of natural radiation. They also get exposed to tiny amounts through sitting in airplanes, routine chest or dental x-rays, and larger amounts through medical tests such as CT-scans and MRIs. A single-organ CT scan, for example, gives a radiation dose of about 6,900 microsieverts.

* On Sunday afternoon, radiation levels in central Tokyo were around 0.16 microsieverts per hour. That is a level experts describe as minimal, and just below the global average of naturally occurring background radiation of 0.17-0.39 per hour, a range given by the World Nuclear Association. It is also significantly lower than the cosmic radiation of up to 7 microsieverts per hour experienced on a Tokyo-New York flight.

Below are different levels of massive radiation exposure in a single dose -- all measured in millisieverts -- and their likely effects on humans, as published by the U.S. Environmental Protection Agency:

- 50-100: changes in blood chemistry

- 500: nausea, within hours

- 700: vomiting

- 750: hair loss, within 2-3 weeks

- 900: diarrhea

- 1,000: hemorrhage

- 4,000: possible death within 2 months, if no treatment

- 10,000: destruction of intestinal lining, internal bleeding and death within 1-2 weeks

- 20,000: damage to the central nervous system and loss of consciousness within minutes, and death within hours or days

Sources: Reuters, Taiwan Atomic Energy Council, World Nuclear Association, US Department of Transportation, US Environmental Protection Agency

=======================================================

Radiats Biol Radioecol. 2007 May-Jun;47(3):286-91.

Mechanisms of action for an anti-radiation vaccine in reducing the biological impact of high dose and dose-rate, low-linear energy transfer radiation exposure.

Maliev V, Popov D, Casey RC, Jones JA.

Vladicaucasian Scientific Center, Russian Academy of Sciences, Biotechnology Departament, Russia.

Abstract

The development of an anti-radiation vaccine could be very useful in reducing acute radiation syndromes. Existing principles for the treatment of acute radiation syndromes are based on the amelioration of progressive pathophysiological changes, using the concept of replacement therapy. Active immunization by small quantities of the essential radiation-induced systemic toxins of what we call the Specific Radiation Determinant (SRD) before irradiation increased duration of life among animals that were irradiated by lethal or sub-lethal doses of gamma-radiation. The SRD toxins possess antigenic properties that are specific to different forms of acute radiation sickness. Intramuscular injection of larger quantities of the SRD toxins induce signs and symptoms in irradiated naive animals similar to those observed in acute radiation syndromes, including death. Providing passive immunization, at variable periods of time following radiation, with preparations of immune-globulins directed at the SRD molecules, can confer some protection in the development of clinical sequelae in irradiated animals. Improved survival rates and times were observed in animals that received lower, sublethal doses of the same SRDs prior to irradiation. Therefore, active immunization can be induced by SRD molecules as a prophylaxis. The protective effects of the immunization begin to manifest 15-35 days after an injection of a biologically active SDR preparation. The SRD molecules are a group of radiation toxins with antigenic properties that correlate specifically with different forms of radiation disease. The SRD molecules are composed of glycoproteins and lipoproteins that accumulate in the lymphatic system of mammals in the first hours after irradiation, and preliminary analysis suggests that they may originate from cellular membrane components. The molecular weight of the SRD group ranges from 200-250 kDa. The SRD molecules were isolated from the lymphatic systems of laboratory animals that were irradiated with doses known to induce the development of cerebral (SRD-1), non-specific toxic effects (SRD-2), gastrointestinal (SRD-3) and hematological (bone marrow) (SRD-4) syndromes. Our results suggest that an anti-radiation vaccine can be developed for prophylactic use against radiation damage induced by acute exposure to significant doses of low Linear Energy Transfer (LET) radiation for humans, including nuclear power workers, commercial and military pilots, cosmonauts/astronauts, nuclear-powered engine vessel operators and possibly even the civilian population in the case of a nuclear terrorism event.

PMID: 17867496 [PubMed - indexed for MEDLINE]

30/03 Cellphone Radiation May Alter Your Brain. Let’s Talk.

March 30, 2011
By KATE MURPHY

In a culture where people cradle their cellphones next to their heads with the same constancy and affection that toddlers hold their security blankets, it was unsettling last month when a study published in The Journal of the American Medical Association indicated that doing so could alter brain activity.

The report said it was unclear whether the changes in the brain — an increase in glucose metabolism after using the phone for less than an hour — had any negative health or behavioral effects. But it has many people wondering what they can do to protect themselves short of (gasp) using a landline.

“Cellphones are fantastic and have done much to increase productivity,” said Dr. Nora Volkow, the lead investigator of the study and director of the National Institute of Drug Abuse at the National Institutes of Health. “I’d never tell people to stop using them entirely.”

Yet, in light of her findings, she advises users to keep cellphones at a distance by putting them on speaker mode or using a wired headset whenever possible. The next best option is a wireless Bluetooth headset or earpiece, which emit radiation at far lower levels. If a headset isn’t feasible, holding your phone just slightly away from your ear can make a big difference; the intensity of radiation diminishes sharply with distance. “Every millimeter counts,” said Louis Slesin, editor of Microwave News, an online newsletter covering health and safety issues related to exposure to electromagnetic radiation.

So crushing your cellphone into your ear to hear better in a crowded bar is probably a bad idea. Go outside if you have to take or make a call. And you might not want to put your cellphone in your breast or pants pocket either, because that also puts it right up against your body. Carry it in a purse or briefcase or get a nonmetallic belt clip that orients it away from your body.

Some studies have suggested a link between cellphone use and cancer, lower bone density and infertility in men. But other studies show no effect at all. Given the mixed messages and continuing research, Robert Kenny, a Federal Communications Commission spokesman, said in an e-mail, “As always, we will continue to study this issue and coordinate with our federal partners.”

The phone used in Dr. Volkow’s study was a Samsung Knack, model SCH-U310, a flip phone that was in wide use when she began planning her experiments two and half years ago. But today’s ubiquitous smartphones emit even more radiation as they transmit more, and more complex, data.

You can get an idea of the relative amounts of radiation various cellphone models emit by looking at their SAR, or Specific Absorption Rate. This number indicates how much radiation is absorbed by the body when using the handset at maximum power. A cellphone cannot be sold in the United States unless an F.C.C.-approved laboratory says its SAR is below 1.6 watts per kilogram. In Europe, the maximum is 2 watts per kilogram.

The SAR number is not displayed when you compare cellphones at your local wireless store, and trying to find it in the fine print of your user manual is an exercise in frustration. The F.C.C. maintains that SAR values “do not provide sufficient information” to reliably compare cellphone radiation emissions because certain phones might rarely operate at maximum power. Still, the Environmental Working Group, a nonprofit organization, has a comprehensive list of the SAR values for most cellphones available from major carriers on its Web site. (For instance, the Apple iPhone 4 is listed at 1.17 watts per kilogram, the Motorola Droid at 1.5 and the LG Quantum at 0.35.)

But more important than looking for a low-SAR phone is how you use it. Many cellphones emit the most radiation when they initially establish contact with the cell tower, making their “digital handshake.” To reduce exposure it’s best to wait until after your call has been connected to put your cellphone next to your ear.

During the ensuing conversation, it’s advisable to tilt the phone away from your ear when you are talking and only bring it in close to your ear when you are listening. That bit of teeter-totter works because the emission of radiation is “significantly less when a cellphone is receiving signals than when it is transmitting,” said Lin Zhong, assistant professor of electrical and computer engineering at Rice University in Houston.

Moreover, your cellphone emits less when you are stationary because when you are moving rapidly — say, in a car or train — it must repeatedly issue little bursts of radiation to make digital handshakes with different towers as it moves in and out of range. (More cause to hang up when you buckle up.)

Want another reason to complain about your carrier’s poor coverage? Any situation where your cellphone has a weak signal indicates it has to work harder and thus will emit more radiation. “Fewer bars means more radiation,” said Om Gandhi, professor of electrical engineering at the University of Utah in Salt Lake City. Inside buildings and elevators, in rural areas, the Grand Canyon — these are not good places to make a call if you’re trying to reduce your exposure to radiation.

Of course, parents using their iPhones to pacify cranky kids might want to reconsider rattles. Children’s developing brains and tissues are thought to be most vulnerable to cellphone radiation. Health authorities in Britain, France, Germany and Russia have all issued warnings against allowing small children to use cellphones for extended periods, if at all.

There are cellphone attachments that purport to shield users from radiation, and most are “hoaxes,” said Mr. Gandhi. Beware of pendants that sellers claim snatch radiation from the air. Pong Research offers a cellphone case for iPhones and BlackBerrys that it says has been shown by an F.C.C.-approved testing lab to redirect radiation from the phone’s antenna away from the head.

While the manufacturer says it reduces radiation more than 60 percent, some electrical engineering experts question whether the case may have the opposite effect at orientations where your head is in the way of the cell tower because your phone may have to increase its transmission strength somewhat to compensate for the redirected signal. The company disputes this. Nevertheless, the net effect of using the device throughout the course of the day may be a reduction in total exposure.

Texting, instead of talking, might be safer. “The whole trend toward texting instead of talking on cellphones is probably a good thing,” said Mr. Slesin at Microwave News.

That is, if you don’t rest your cellphone against your body while typing out your message.



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24/03 Gov't should clearly explain health risks of radioactive contamination

Gov't should clearly explain health risks of radioactive contamination

In this photo released by Tokyo Electric Power Co. (TEPCO), gray smoke rises from Unit 3 of the tsunami-stricken Fukushima Dai-ichi nuclear power plant in Okumamachi, Fukushima Prefecture, Japan, Monday, March 21, 2011. Official says the TEPCO temporarily evacuated its workers from the site. At left is Unit 2 and at right is Unit 4. (AP Photo/Tokyo Electric Power Co. )

The effects of radioactive contamination of food and drinking water are spreading as workers struggle to handle a nuclear power plant crisis in Fukushima Prefecture.

Following warnings in parts of Fukushima Prefecture, the Tokyo Metropolitan Government recommended that infants in Tokyo should not drink tap water. The government has halted shipments of unprocessed milk and some vegetables produced in Fukushima Prefecture, among other areas, and is asking people not to consume these products.

The government message that has accompanied such warnings is: "These products won't harm your health. But just in case, we don't want you to eat or drink them."

Just how should we receive this seemingly contradictory message? Food and water form the foundation of people's existence. Naturally, the government should boost the monitoring of products to accurately grasp the state of contamination, but that alone won't solve the problems that have emerged.

In areas damaged by the March 11 earthquake and tsunami, food and other materials are still in short supply. The government should consider the circumstances in these areas and improve its risk management and communication.

If there are going to be restrictions on the intake of water and some food products, then the government must prepare a system to deliver replacement products to disaster-hit areas. People have been left wondering what they should do if they can't obtain replacement products, and what risks infants and pregnant women face. The government must carefully address such concerns.

If officials want people to reach calm decisions -- not just about the safety of food and water but also about the radiation in the air -- then they must do more than occasionally dishing out figures and their interpretations of them.

How much radiation have the people living in affected areas been exposed to in total? When officials say there is no health risk if people are exposed to radiation for a long time, exactly how long is a "long time"? And what does the term "health effects" actually mean? If the government wants people to remain calm then it must answer such questions in clearer terms.

Officials should also clearly state whether radiation around the nuclear power plant is declining or not and how the situation is expected to develop. Information regarding the transition of radiation levels in Fukushima Prefecture would be helpful in determining the outlook for Tokyo, too.

Understandably, it is difficult to accurately measure the physical effects of exposure to low levels of radiation. Still, the threat of damage to DNA, resulting in cancer, is worrying. The human body is equipped to repair such damage, but when the level of damage is high, the long-term risks cannot be ignored.

After the Chernobyl nuclear power plant disaster, thyroid cancer emerged among children who continued to drink milk contaminated with radioactive iodine. Surely a priority for the Japanese government is to come up with ways to protect children, while explaining that the situation in Japan is different. If people over a certain age are not at risk, then the government should clearly say so.

In handling the situation, the government must ensure residents stay well even if radioactive contamination continues. It must not let people move about in confusion trying to get their hands on uncontaminated food and water.

(Mainichi Japan) March 24, 2011

30/03 Trying to keep morale up

The Yomiuri Shimbun

The cold really seeps in at night, but workers in the 35-square-meter main office and hallways sleep packed together like sardines. Some line up a few chairs to spend the night on.

TEPCO employees who were at the power station when the earthquake hit on March 11 worked 23-hour shifts for the first few days, with time for only a one-hour nap each day.

With radiation levels outside as high as ever, the workers have put lead sheets on the floor of the earthquake-resistant building they are staying in, reducing radiation inside to between two microsieverts and three microsieverts per hour.

Very high levels of radiation have been measured in puddles of water in the turbine buildings.

"I can't emphasize enough how important it is for workers to avoid those puddles" while carrying out their duties, said Kazuma Yokota, an inspection chief at the Nuclear and Industrial Safety agency who stayed five days at the plant last week. Most workers are rotated out regularly in shifts, "but it's difficult for the management to leave," he said.

After a meeting at night, everyone gathers around for a group cheer. "Let's do our best!" they cry out with a synchronized clap, trying to boost morale.

"Considering the importance of the work they're doing, they aren't getting enough support," said Tokyo Women's Christian University Prof. Hirotada Hirose, a specialist in disaster and risk psychology. "This situation where they're not getting enough food or sleep will make them less efficient and increase the possibility of mistakes."

Hirose said working conditions could be improved by providing nutritional supplements and vitamins, plus making sure the workers have enough sleeping bags.

(Mar. 30, 2011)

30/03 Balancing act at reactors / Water vital for cooling, but drainage poses new set of problems

The Yomiuri Shimbun

Work to remove radiation-contaminated water from the turbine buildings of reactors at the Fukushima No. 1 nuclear power plant moved into full gear Tuesday, while efforts continued to cool the reactors with water.

Plant operator Tokyo Electric Power Co. earlier confirmed radioactive water that spilled out of the reactors had collected in underground trenches connected to them.

Workers were scrambling to prevent the contaminated water in the trenches from leaking into the sea. For instance, work was continuing around the clock to transfer water from the first basement floor of the No. 1 reactor's turbine building to a condenser.

The condensers at the Nos. 1 and 4 reactors still had room for more water as of Tuesday, but the condensers at the Nos. 2 and 3 reactors were already full to capacity.

At the No. 3 reactor, there were renewed efforts to transfer water in the condenser to a tank outside the building, and then to other tanks.

The top priority at the plant is to cool the reactors, but the dilemma facing workers is that the cooling process produces more contaminated water, which is time-consuming and troublesome to clear.

To minimize the amount of leaking water, water used to cool the reactors must also be kept as small as possible. But if too little cooling water is used, reactor temperatures will rise.

At the No. 2 reactor, water became contaminated with radioactive material during the cooling process, and is believed to have then leaked into the turbine building from the reactor containment vessel.

Late Sunday night, TEPCO reduced the amount of water being injected into the No. 2 reactor, from around 17 tons per hour to 7 tons per hour.

The temperature in the reactor pressure vessel, which had been about 125 C, increased to 148 C by 7 p.m. Monday and 152 C by 2 a.m. Tuesday.

Also at 2 a.m. Tuesday, at the No. 1 reactor, the temperature and pressure inside the pressure vessel were unstable. The amount of cooling water being injected has increased since Monday night in an attempt to suppress the rise in temperature that began Saturday.

As of 6 a.m. Tuesday, the temperature was stable at 323.3 C, slightly lower than it had been four hours earlier.

TEPCO is carefully monitoring conditions to assess whether the temperature had been brought under control.

At the No. 3 reactor, where the condenser is already full, the focus was on removing water from a makeup water tank--an outdoor tank for temporarily storing water from the reactor--and transferring it to empty water-storage tanks for storing water for pressure suppression chambers. These empty tanks, also located outdoors, are situated south of the No. 4 reactor.

Emptying the makeup tank will allow TEPCO to remove water from the condenser in the turbine building, and then transfer contaminated water from inside the building into the condenser.

Chief Cabinet Secretary Yukio Edano said a scenario where nuclear fuel is not being cooled by water has to be prevented by any means.

"A situation where fuel is burning without any water must be avoided. The cooling work should be prioritized," Edano said. He also stressed the importance of using as little water as possible.

(Mar. 30, 2011)

30/03 Plutonium detected in soil at N-plant

The Yomiuri Shimbun

Small amounts of three plutonium isotopes were detected in soil sampled at the Fukushima No. 1 nuclear power plant last week, but the levels do not pose a health risk, plant operator Tokyo Electric Power Co. has announced.

Plutonium-238, 239 and 240 were detected in soil samples taken at five locations inside the plant between the afternoon of March 21 and the morning of March 22 morning, TEPCO said Monday night.

"This is quite serious since it indicates fuel rods have melted to some degree," Chief Cabinet Secretary Yukio Edano said at a Tuesday morning press conference. Edano stressed the need to increase monitoring in the surrounding area.

Plutonium has been detected before after atmospheric nuclear weapons tests, but TEPCO said the plutonium measured this time was likely from the crippled reactors, judging from its characteristics. Only small amounts of substances used as nuclear fuel exist in nature.

The Japan Atomic Energy Agency conducted the analysis of the soil samples from March 23. It usually takes about a week to complete plutonium-detecting tests.

Levels of plutonium-238--a radioactive nuclide generated in nuclear reactors--in samples from a multipurpose field and a solid waste warehouse were 0.54 becquerels and 0.18 becquerels per kilogram of soil, respectively. The former amount is about 3.6 times the level normally detected domestically.

TEPCO Vice President Sakae Muto said in a press conference in Tokyo that plutonium-238 detected came from the recent crisis at the plant. Plutonium-238 made up a higher percentage of the samples than the other isotopes.

The plant's No. 3 reactor uses MOX fuel, a mix of uranium and plutonium. However, since plutonium is generated even when only regular uranium fuel is used, it is unknown which reactor was the source of the plutonium that was detected, Muto said.

Other radioactive substances that have been detected in and around the Fukushima No. 1 plant, such as iodine-131, are believed to have been generated in the reactors. TEPCO officials suspect plutonium was released together with these substances.

"I think the plutonium came from damaged nuclear fuel rods in the reactors, and escaped when water leaked out," said nuclear chemist Michiaki Furukawa, professor emeritus at Nagoya University.

"But it won't affect humans seriously since the amounts detected were very small. Also, since plutonium doesn't vaporize easily, it can't be carried far away by the wind," He said. "It's dangerous when it gets into the lungs but it hasn't been dispersed outside the plant."

TEPCO said it would continue taking soil samples to check for radioactive substances.

Plutonium is produced when uranium atoms are exposed to neutrons. It can be used as nuclear fuel similar to uranium. Plutonium's weight changes depending on the number of neutrons it has. There are several isotopes, including plutonium-238 and 239.

Plutonium, an alpha-ray emitter, has a very weak penetrating force. The risk of external exposure is therefore low. If plutonium is eaten, it is easily excreted, but if it is inhaled, it stays in the lungs and can cause cancer.

(Mar. 30, 2011)

30/03 Nhật Bản nâng mức báo động tối đa

Thanh Niên – 09:56 Thứ tư, ngày 30 tháng ba năm 2011

Nhật Bản đang được đặt vào tình trạng báo động tối đa sau khi giới chức phát hiện plutonium trong đất xung quanh Nhà máy Fukushima số 1.

Kyodo News dẫn lời Chánh văn phòng Nội các Nhật Bản Yukio Edano hôm qua cho biết, các chuyên gia của Cơ quan An toàn công nghiệp và hạt nhân (NISA) đã tìm thấy một lượng nhỏ 3 đồng vị plutonium trong những mẫu đất xung quanh Nhà máy điện hạt nhân Fukushima số 1. Dù hàm lượng các đồng vị Pu-238, Pu-239 và Pu-240 trong đất không gây nguy hiểm tức thời cho con người khi tiếp xúc ngoài da, nhưng ông Edano thừa nhận diễn biến trên cho thấy sự việc nghiêm trọng hơn người ta vẫn tưởng. Đặc biệt, các mẫu đất trên được lấy từ hôm 21 và 22.3, trước cả khi tình hình ở Nhà máy Fukushima số 1 trở nên cực kỳ phức tạp vào cuối tuần qua.
Việc phát hiện plutonium, chỉ thoát khỏi các thanh nhiên liệu phóng xạ trong điều kiện nhiệt độ cực cao, là minh chứng chắc chắn nhất cho thấy tình trạng hư hại tại nhà máy nói trên đang rất trầm trọng, Kyodo News dẫn lời phát ngôn viên Hidehiko Nishiyama của NISA. Plutonium là sản phẩm phụ trong các phản ứng hạt nhân và cũng là một phần của hỗn hợp nhiên liệu tại lò phản ứng số 3, lò duy nhất tại Nhà máy Fukushima số 1 sử dụng nhiên liệu này. Plutonium độc hại hơn cả uranium, có thể đe dọa nghiêm trọng đến sức khỏe con người nếu xâm nhập cơ thể qua đường hô hấp hoặc ăn uống, nhưng không gây tác hại lắm khi tiếp xúc ngoài da, theo Cơ quan Bảo vệ môi trường Mỹ.

Khi phân hủy, plutonium thải ra phân tử gọi là alpha, mang nhiều năng lượng. Khi hạt alpha nhiễm vào mô cơ thể, nó có thể hủy hoại ADN của tế bào và dẫn đến tình trạng đột biến gây ung thư hết sức nghiêm trọng. Đó là lý do giới khoa học liệt plutonium vào loại vật chất nguy hiểm nhất từng tồn tại trên Trái đất. Do thuộc dạng nguyên tố nặng, plutonium khó kết hợp với các nguyên tố khác, nên ít khi nào tìm thấy plutonium lan rộng như đồng vị phóng xạ của các chất nhẹ hơn như caesium và i-ốt. Cũng vì vậy mà chu kỳ bán rã của nó kéo dài rất lâu, với Pu-239 phải trả qua 24.000 năm mới mất đi phân nửa hoạt động phóng xạ, còn chu kỳ bán rã của Pu-238 và Pu-240 lần lượt là 87 năm và hơn 6.500 năm. Nói tóm lại, như CNN dẫn lời Alan Lockwood, giáo sư của Đại học Buffalo (Mỹ): “Nếu bạn hít phải khí độc này, nó sẽ tồn tại trong cơ thể bạn đến chết”.

Xem xét mở rộng vùng di tản

Việc tìm thấy plutonium trong đất đai xung quanh Nhà máy Fukushima số 1 cũng cho thấy vành đai phòng vệ xung quanh lò phản ứng số 3 và của nhà máy đã gặp vấn đề. Trong lúc đó, chính phủ của Thủ tướng Naoto Kan đang đối mặt với áp lực ngày một tăng từ phe đối lập về chuyện mở rộng khu vực di tản xung quanh Nhà máy Fukushima số 1. Reuters dẫn lời ông Kan cho biết đang hỏi ý kiến chuyên gia về chuyện mở rộng bán kính vùng di tản bắt buộc, đồng nghĩa với việc có thêm 130.000 người phải sơ tán so với con số 70.000 người trước đó. Thủ tướng Kan cũng khẳng định Nhật Bản đang được đặt trong tình trạng báo động cao nhất, do cuộc khủng hoảng hạt nhân và tại khu vực bị sóng thần tàn phá vẫn có những diễn biến khó lường. Trước tình trạng rò rỉ plutonium cùng với nước nhiễm xạ cao, các chuyên gia khẳng định ưu tiên trong lúc này vẫn là chuyện hút nước nhiễm xạ ra khỏi các lò phản ứng của nhà máy một cách an toàn.

Trong một diễn biến khác, tờ Yomiuri Shimbun hôm qua đưa tin chính phủ đang cân nhắc quốc hữu hóa Công ty điện lực Tokyo (TEPCO), đơn vị quản lý Nhà máy Fukushima số 1, sau nhiều sai sót trong việc giải quyết cuộc khủng hoảng.

Thụy Miên