12/05 福島第１原発：構内のグラウンドからプルトニウムを検出

　東京電力は１２日、福島第１原発の構内にあるグラウンドから、毒性の強い放射性物質のプルトニウムを検出したと発表した。検出されたのは、プルトニウム２３８、同２３９、同２４０。東電はいずれも今回の事故によって放出された物質とみているが、土壌１キロあたりの濃度は同２３８の０．１１ベクレルが最大だったため、過去の大気圏核実験で日本に降ったものと同等のレベルにとどまり、人体への影響はないと説明している。

　同２３９と同２４０の濃度は、土壌１キロあたり０．０４６ベクレルだった。東電によると、３月２１日以降に週２回測定している値からの大きな変化はない。【久野華代】

• 福島第１原発：１２日は７０人が一時帰宅　除染などはなし
• 福島第１原発：１号機、燃料の大半「溶融」…冷却は維持
• 福島第１原発：事故調、３チームで検証　海外専門家も助言
• 福島第１原発：３号機取水口で汚染水　ピットから海へ流出
• 福島第１原発：上空放射線量、通常の数倍も　福島大調査

毎日新聞　2011年5月12日　20時43分

03/05 High level radiation found on seabed near Japan's crippled nuke plant

2011-05-03 21:27:45

TOKYO, May 3 (Xinhua) -- Radiation readings that are 100-1,000 times the normal level have been found on the Pacific seabed near the crippled Fukushima No. 1 nuclear power plant, local media reported Tuesday.

The high levels of radioactive materials were detected from samples taken Friday from the seabed at points 20-30 meters deep, Kyodo News reported, citing the plant's operator Tokyo Electric Power Co.

The Japanese government and the utility have been battling to keep the plant crippled by the devastating earthquake and tsunami in March under control. It is still leaking radioactive substances into environment.

Special Report: Massive quake shakes Japan

25/04 Atmospheric radiation leak underestimated

The Yomiuri Shimbun

Data released by the government indicates radioactive material was leaking into the atmosphere from the Fukushima No. 1 nuclear power plant in early April in greater quantities than previously estimated.

Radioactive material was being released into the atmosphere from the plant at an estimated rate of 154 terabecquerels per day as of April 5, according to data released by the Cabinet Office's Nuclear Safety Commission on Saturday.

The NSC previously estimated radiation leakage on April 5 at "less than 1 terabecquerel per hour."

Iodine-131 and cesium-137 were released into the atmosphere that day at the estimated rates of 0.69 terabecquerel per hour and 0.14 terabecquerel per hour, respectively, the NSC said.

Emissions are converted into iodine-131 equivalents for assessment on the international nuclear event scale (INES), to arrive at the total 154 terabecquerels per day, the nuclear safety watchdog said.

One terabecquerel equals 1 trillion becquerels.

On April 17, plant operator Tokyo Electric Power Co. said in its plan for stabilization of the crippled reactors it would not start to get radiation leakage under control until the plan's fourth month of implementation.

This would mean 10,000 terabecquerels of radioactive substances would be released into the atmosphere from the plant during the coming three months, according to simple calculations based on the estimated emission rate as of April 5.

Emissions in that three-month period alone would therefore exceed the level necessary for a Level 6 severity rating on the INES, the globally accepted measure for evaluating nuclear accidents.

The ongoing crisis at the Fukushima plant has been rated a maximum Level 7 on the scale, which was established by the International Atomic Energy Agency and the Organization for Economic Cooperation and Development in 1992.

The total amount of radioactive material discharged from the plant from March 11 to early April was estimated between 370,000 and 630,000 terabecquerels, according to government sources.

The commission, however, said the figures were estimates only, "with a considerable margin of error." Radiation levels around the six-reactor complex have been slowly falling, it said.

(Apr. 25, 2011)

23/04 高放射線量がれき発見…保安院すぐに公表せず

　経済産業省原子力安全・保安院は２３日、東京電力が福島第一原子力発電所３、４号機の近くで毎時９００ミリ・シーベルトに達する高放射線量のがれきを発見し、撤去したと発表した。

　これまでに確認されたがれきの放射線量は、最高でも毎時１００～２００ミリ・シーベルト程度で、今回のがれきは「３号機の水素爆発と関連している可能性がある」と説明している。

　見つかったのは、縦横が各３０センチ、厚さ５センチのコンクリート片。東電が２０日午後に見つけ、２１日に有人の重機で鋼製コンテナに回収した。コンテナから約１メートルの距離で測った線量は、毎時１・１ミリ・シーベルトに落ちていたという。

　保安院は、コンクリート片の発見後すぐに東電から報告を受けていたが、公表していなかった。西山英彦審議官は、「今後は、分かったことはすぐに公表したい」と話している。

（2011年4月23日20時56分 読売新聞）

23/04 Sea leaks would be rated Level 5 or 6

The Yomiuri Shimbun

If estimates of leaks of radioactive material into the sea from Tokyo Electric Power Co.'s stricken Fukushima No. 1 nuclear power plant were judged according to the International Nuclear Event Scale, the severity of marine contamination would be rated Level 5 or 6.

The Three Mile Island nuclear accident in the United States was rated Level 5 on the scale introduced by the International Atomic Energy Agency that runs from zero to seven and is based on radiation leaks into the atmosphere.

The radiation leaks into the sea have caused serious contamination of the marine environment, TEPCO's estimates show. Water that leaked into the Pacific Ocean from the No. 2 reactor's water intake contained an estimated 4,700 terabecquerels of radioactive substances, TEPCO announced Thursday.

On April 4-5, the company took the emergency action of discharging 10,000 tons of relatively low-level radioactive water from a fuel waste disposal facility, causing an international stir.

The estimated total amount leaked, 4,700 terabecquerels, is 30,000 times the amount of radioactive material contained in the water discharged on April 4-5.

It is also about 20,000 times the amount of radioactive substances the plant is legally permitted to release into the environment in a year. One terabecquerel equals 1 trillion becquerels.

On April 12, the government's Nuclear and Industrial Safety Agency raised the severity level of the ongoing crisis to Level 7, citing the estimated 370,000 terabecquerels of radiation released into the air from the reactors.

TEPCO has said leakage into the sea started April 1, but records show radiation levels in seawater peaked on March 31. It is therefore highly likely that radioactive water leaked into the ocean before April 1.

Jun Misono, a senior researcher of the Marine Ecology Research Institute, said: "At the moment, [radiation] levels higher than government-set limits have been detected in small fish that eat plankton. Tests should also be conducted on various other marine species."

In the past, accidents outside Japan have resulted in sea contamination. At the Sellafield nuclear facility in Britain, massive amounts of radioactive substances were discharged into the sea for 30 years until the 1980s. The total amount remains unknown, but according to a Norwegian research institute, the leak peaked in 1975 with radiation of about 9,000 terabecquerels.

(Apr. 23, 2011)

08/04 汚染、「飛び地」状も セシウムの健康被害は未確認 チェルノブイリ事故

2011年4月8日11時6分

チェルノブイリ原発事故による放射能汚染（「チェルノブイリ事故による放射能災害」今中哲二編　から）

　１９８６年に起きたチェルノブイリ原発事故では、原子炉の試験運転中に大きな水蒸気爆発が起きた。１０日間にわたり、放射性物質の大量放出が続き、原発から数百キロと極めて広い範囲に拡散した。福島第一原発の事故は、運転を停止した後に起きており、放射性物質が多く飛散したのは、避難地域を中心に限定的だ。

　旧ソ連政府などは、土壌のセシウム１３７の値が１平方メートルあたり３万７千ベクレル（１００万分の１キュリー）を超えた地域を「汚染地域」、５５万５千ベクレル（１００万分の１５キュリー）を超えた地域を「強制移住地域」とした。

　セシウム１３７は半減期が３０年と長いため、土壌汚染の指標として使われる。

　国際原子力機関（ＩＡＥＡ）の報告によると、旧ソ連の汚染地域は約１４万５千平方キロメートルと、日本の面積の約４割に上った。その地域に住んでいた住民数は、約６００万人に上る。強制移住地域は、岐阜県の面積に匹敵する約１万平方キロメートルで、約２７万人が対象となった。

　しかしこの汚染地域も風向きなど気象条件により、原発から同心円状ではなく、まだら状に広がっている。東側に４００～６００キロの範囲に、飛び地のように広がった地域もある。

　汚染地域に住み続けた人が８６～２００５年に受けた放射線量の積算値の平均は１０～２０ミリシーベルト。強制移住地域に住み続けた人の積算値は、５０ミリシーベルトを超えたという。しかし、国際機関と共同でチェルノブイリでの健康調査を実施してきた山下俊一・長崎大教授（被曝〈ひばく〉医療）によると、セシウム１３７の影響を受けた健康被害は確認されていないという。

　山下さんは「現地の人は汚染されたキノコや野菜を食べ続け、体内にセシウム１３７を５００～５万ベクレルぐらい持っている。しかし、何ら疾患が増えたという事実は確認されていない」と話している。

　◆キーワード

　〈ベクレルとシーベルト〉　ベクレルは放射能の強さを測る単位。シーベルトは人間が放射線を浴びたときの影響度を示す単位。ベクレルをシーベルトに換算するには、放射性物質の種類、飲食や吸入など体内に入るルートで異なる係数をかける必要がある。放射性ヨウ素について、水や牛乳での１キログラム当たりの規制値である３００ベクレル分を口にすると、人体への影響は６．６マイクロシーベルトで、胃のＸ線集団検診を１回受けたときの約９０分の１に相当する。

19/04 TEPCO must provide more solid information on recovery from nuclear crisis

In this image released Saturday, April 16, 2011, by Tokyo Electric Power Co., top of the container of the nuclear reactor, painted in yellow, of Unit 4 at the Fukushima Dai-ichi Nuclear Plant is observed from its side with a T-Hawk drone Friday, April 15, 2011 in Okuma, Fukushima Prefecture, northeastern Japan. (AP Photo/Tokyo Electric Power Co.)

Layout of cooling systems at Fukushima No.1 Power Plant. (Mainichi)

Just when will people be able to breathe a sigh of relief that the crisis at the Fukushima No. 1 Nuclear Power Plant is over? The lives of residents living around the plant are hanging on an answer to this question. For local farmers and businesses, it is a matter of life and death.

Tokyo Electric Power Co. (TEPCO)'s announcement of a schedule for bringing the disaster under control was significant. Unfortunately, however, the schedule lacks concrete details. Rather than serving as a plan to solve the crisis it is a display of just how many difficulties remain.

Radioactive materials continue to leak from the plant's reactors, but the source of the leaks and the exact times materials have leaked remain unclear. To control the leaks, the reactors must be cooled to under 100 degrees Celsius and stabilized -- a process known as a "cold shutdown."

TEPCO's schedule says it will take six to nine months for reactors to be brought to a cold shutdown. But when looking squarely at the schedule, it seems unlikely that the process will be completed within this time frame. A year is probably more realistic.

In this image released by Tokyo Electric Power Co., a radio-controlled PakBot robot opens a door inside the reactor building of Unit 2 as it is monitored with another Pakbot from behind during inspection of the tsunami-damaged facilities at the Fukushima Dai-ichi Nuclear Power Plant Monday, April 18, 2011 in Okuma, Fukushima Prefecture, northeastern Japan.

The power company says that it will first drench the containment vessels of the plant's No. 1 and 3 reactors -- including the pressure vessels -- in water. But if the containment vessels are damaged, water will leak out. Drenching the containment vessels in water is something that has not been done before when handling a nuclear power plant accident, and workers must be well aware of the strength of containment vessels.

But even if this first stage goes well, a cold shutdown will not immediately follow. Water must be circulated in a closed loop to continually remove heat from the nuclear fuel.

The containment vessel of the No. 2 reactor has almost certainly been damaged. Plans to patch up the damage have been drawn up, but radiation levels around the reactor must first be reduced. Because of this, it remains unclear if such work will actually be possible. And even if another device to continually remove heat from the fuel is built, unforeseen problems could occur.

TEPCO should form plans to address each of these issues while taking alternative solutions into consideration, and produce a concrete appraisal of the situation. In doing so, it is vital to confirm the state of damage to the nuclear reactors and pipes. Which parts are damaged and what is the extent of the damage? Workers may not be able to view every part up close, but TEPCO should provide solid information on each possibility.

Overall there has been a lack of information regarding the nuclear power plant. We still don't know the amount of radioactive materials that continue to leak from the power plant. TEPCO's schedule says it will expand and enhance its monitoring of radiation within three months, but the company should make an effort to speed this process up and do its job of releasing information. Otherwise, residents will find it difficult to draw up plans for their futures.

This Sunday, April 10, 2011 photo released by Tokyo Electric Power Co. (TEPCO) shows orange colored floats suspending"silt fence," that was installed under water to help prevent contaminated water from spreading outside the Fukushima Dai-ichi nuclear power plant's bay. (AP Photo/Tokyo Electric Power Co.)

The process of bringing a nuclear power plant accident under control must be measured in years, not months. The work to achieve a solution must be shared, and a system to handle the crisis over the long term must be developed. The release of detailed information will form the pillars of these efforts.

Click here for the original Japanese story

(Mainichi Japan) April 19, 2011

05/04 Radiation fallout from Fukushima plant will take "months" to stop

2011/04/05

Contaminated water gushes out of a crack in a wall at the Fukushima No. 1 nuclear power plant on Saturday. (Provided by Tokyo Electric Power Co.)

Editor's note: We will update our earthquake news as frequently as possible on AJW's Facebook page: http://www.facebook.com/AJW.Asahi. Please check the latest developments in this disaster. From Toshio Jo, managing editor, International Division, The Asahi Shimbun.

* * *

The government on Sunday acknowledged for the first time that it would take several months before radioactive materials stopped leaking from the crippled Fukushima No. 1 nuclear power plant.

Goshi Hosono, special adviser to Prime Minister Naoto Kan for the Fukushima crisis, told reporters: "We cannot allow radiation to go on being emitted. Yet while we have to resolve that problem as quickly as possible, it will likely take several months to achieve that goal."

Hosono is coordinating cooperation efforts with the United States to deal with the plant.

Chief Cabinet Secretary Yukio Edano also said Sunday, "It will take months to cool (the reactors) and to implement measures to prevent (radiation) from spreading."

At a Friday news conference, Kan also said the government would have to be prepared for a protracted fight to resolve the issue.

The setting of a general time frame likely means that the government wants to show it has a long-term commitment to the situation, rather than merely haphazardly fixing problems when they arise.

Firefighting pipes are now being used to pump in large volumes of water into the reactors to cool the fuel in the cores. However, highly radioactive water is believed to be leaking out of the reactor buildings and flowing into the ocean.

Officials of Tokyo Electric Power Co., the plant operator, want to restore the normal cooling system that would cool both the reactor core and the storage tanks holding the spent fuel rods. Doing so would allow sufficient water to cool the core down to under 100 degrees, at which point it would reach a cold shutdown. The core and storage pool would then become stable and there would be no danger of radioactive materials leaking to the atmosphere through hydrogen explosions, and also no need for water to be pumped into the core.

The time frame of several months given by Hosono is believed to be the time needed to achieve a cold shutdown, but reaching that stage will not be easy. The first task is to remove the contaminated water that has accumulated in the basements of the turbine buildings, which are next to the reactor buildings.

The process, which involves moving water to various pools within the plant ground, is already under way, but it is expected to take at least a week. TEPCO workers want to move the contaminated water in the basements to condensers in the No. 1 to No. 3 reactors. However, the three condensers were already filled with water, so they had to first take that water out and transfer it to the suppression pool storage tanks. This stage has now been completed.

The next step is to move the water from the condensers to their respective condensation storage tanks. This is under way for the No. 1 and No. 2 reactors, and preparations are being made to start on the No. 3 reactor, with the whole process expected to be finished in a few days. After that, the transfer of the contaminated water can finally begin.

Once the water is removed, radiation levels within the buildings will have to be measured to determine if workers can enter to begin the next step.

The March 11 earthquake and tsunami likely caused devastating damage to pipes, valves and pumps within the buildings. Restoring the equipment to normal operations is expected to be a time-consuming procedure.

While those tasks are being performed, water will continue to be pumped into the core to cool both it and the storage pool. That means that highly contaminated water will continue to leak into the outer environment.

Although some causes of the leakage have been determined, some have evaded identification, so stopping the leaks entirely will be another difficult task.

TEPCO workers on Sunday attempted to plug a leak found in a working pit near the seawater intake to the No. 2 reactor, but had not managed to stop the leakage of water into the ocean as of 6 p.m. Sunday.

TEPCO officials are now considering dropping a fence into the ocean to prevent the spread of contaminated water.

The idea being contemplated is to lower a silt fence into the water. Silt fences are used in civil engineering projects to prevent the spread of polluted water. The fence is suspended from a float and extends to the seabed like a curtain and is designed to limit the movement of seawater.

The water off the coast of the Fukushima No. 1 plant has a depth of between five to six meters. One idea being considered is to install the fence near the seawater intake from where contaminated water is flowing as well as near embankments that surround the waters off the plant site.

TEPCO also said Monday it had started pouring low-level radioactive water into the sea. The amount of the relatively uncontaminated water is 11,500 tons at the facilities to process wastewater and in the buildings which house the No. 5 and No. 6 reactors at the Fukushima No. 1 nuclear power plant, it added.

The release of the water may affect fish and seaweed near the plant, but TEPCO officials explain that eating these on a daily basis will total only as much as one-fourth the amount of radiation that people receive from natural sources.

16/03 FAQs on radioactivity exposure, safety

The Yomiuri Shimbun

The following are excerpts from an interview with International University of Health and Welfare Clinic's health care center chief Gen Suzuki about how those people who have been ordered by the government to evacuate can prevent bodily exposure to radioactive material following the hydrogen explosions at the reactors of Tokyo Electronic Power Co.'s Fukushima No. 1 nuclear power plant.

Question: What worries should people have concerning the hydrogen explosion?

Answer: The reactors were placed in reactor containment vessels and these were housed inside buildings. The explosions occurred when a very large amount of hydrogen--created when the reactors were cooled--filled the building. Radioactive substances, such as iodine and cesium, that leaked from the reactors when the explosions occurred dispersed.

Q: Exposure to radiation can occur through contact with radioactive substances?

A: Yes, that's right. If people undergo examinations such as a CT scan, they are exposed to minute amounts of radiation.

Regarding this situation, the substances that emit radiation--not the radiation itself--have dispersed in the surrounding areas. External radiation exposure occurs when particles attach to a person's clothes or skin. Internal radiation exposure occurs after radioactive materials are ingested or absorbed through a wound.

Q: Is it better to stay inside?

A: It depends on how much radioactive materials disperse. But it's better to stay inside to prevent any exposure. If you're asked to stay inside, it is advisable to close all windows and doors, and cut off the external air flow by turning off any ventilators.

Q: What should we do if we have to go outside and evacuate to a shelter?

A: It is advisable to cover up and wear clothes that do not expose the skin as much as possible. Wear a hat and cover your nose and mouth with a wet towel or a mask. When you arrive at your destination, you should first check with authorities if any radioactive materials have adhered to your clothes or skin. If radioactive contamination is confirmed, you must decontaminate yourself.

Q: How do we decontaminate ourselves?

A: Take off your clothes, use wet towels to wipe such substances off yourself or take a shower. Specialists will judge what action should be taken case-by-case based on each shelter's procedures or the level of contamination. The removed clothes should be put in a vinyl bag and tightly secured.

Q: What about being in contact with those who have undergone decontamination procedures?

A: There is no problem because radioactive substances have already been removed. People who have undergone decontamination procedures can resume carrying on as normal.

Q: What about food?

A: Food outside may have been exposed to radioactive substances. You can wash the food but it's better not to eat it at all. Food inside is perfectly okay.

Q: What do you recommend in rainy or snowy weather?

A: It's possible that rain and snow can contain radioactive substances so it is recommended people stay inside. If going outside is unavoidable, follow the same procedures when you are advised to evacuate to a shelter and try to reach your destination as quickly as possible.

Q: How can we determine the level of radiation exposure?

A: Collective measures are used to estimate the exposure levels such as analyzing chromosomes and symptoms, conducting a blood test and using a device to measure internal radiation exposure.

However, there are not many specialists who can perform chromosome analysis and measure internal radiation exposure, so it's not always possible to test individuals at their request. When the nuclear fuel-processing plant accident occurred in Tokaimura, Ibaraki Prefecture, in 1999, tests were given only to patients who had worked at the site, patients who had displayed serious symptoms and to residents who were highly suspected to be exposed to a certain radiation levels.

Other measures to estimate exposure levels are based on facts such as the distance from a nuclear power plant; where you were (inside or outside a building, and whether the building was built of wood or concrete); and when and where you moved. For safety's sake, it's recommended to record your movements.

(Mar. 16, 2011)

23/03 Seawater radioactivity high / Sample shows large iodine concentrations near nuclear plant

The Yomiuri Shimbun

Tokyo Electric Power Co. said Tuesday seawater near an outlet at the quake-hit Fukushima No. 1 nuclear power plant had a concentration of radioactive iodine-131 that was 127 times higher than can be safely ingested by a person continuously for one year, according to government standards.

In a phenomenon called biological concentration, radioactive materials in seawater will become more concentrated in fish and marine plants.

It marked the first time for an analysis of radioactive materials in seawater to be made public since the struggle to contain a meltdown at the nuclear plant began.

As concern mounts over the possible impact on human health and on fishery products if the contamination continues for some time, the government will expand its survey area to get a clearer picture of the radioactive contamination in seawater.

"There should be no impact [on human health] if water of that [level of radioactive contamination] is consumed every day for one year," Chief Cabinet Secretary Yukio Edano said Tuesday. "Yet if the situation continues over time, there may be an adverse impact. We decided to increase our efforts in analyzing it."

He said it was too early to evaluate the impact of the contaminated seawater on fishery products. When asked whether restrictions on shipments would be imposed on marine products, like those taken on some farm products, Edano said it was possible, but it is not yet the time to do so.

Meanwhile, Economy, Trade and Industry Minister Banri Kaieda said, "We have to conduct [water quality] analyses in areas 10 kilometers and 20 kilometers [from the plant] soon."

Kaieda, who doubles as an assistant chief for a headquarters dealing with problems at the nuclear power plant, said the headquarters will send a survey vessel to take seawater samples in these areas.

The Hakoho Maru, a research vessel of the Japan Agency for Marine-Earth Science and Technology, will collect the samples Wednesday, with results of the analysis expected to be announced the following day.

At 2:30 p.m. Monday, TEPCO collected 500 milliliters of seawater at a point 100 meters south of the outlet, from which waste liquid is drained into the sea.

A total of 5.066 becquerel of iodine-131 per milliliter was detected, a level 126.7 times more than the yearly limit a person can safely ingest as set by the Nuclear Reactor Regulation Law.

If a person ingested two liters of water at this level of contamination over a three-day period, it would be equivalent to being exposed to an annual dose of radiation according to government-set safety standards, the Nuclear and Industrial Safety Agency said.

The seawater sample also had a level of cesium-134 that was 24.8 times more than the safety limit, while cesium-137 was 16.5 times above the safety limit.

According to TEPCO, there are two possible causes of the seawater contamination.

One is that the radioactive materials, blasted into the air after explosions at buildings housing the plant's Nos. 1 and 3 reactors, spread toward the Pacific and entered the sea when it rained. The other possible cause is that the water sprayed onto the Nos. 3 and 4 reactors washed the radioactive materials into the sea.

"These aren't levels of contamination that pose an immediate impact," said Junko Matsubara, former professor at Yokohama City University. "Should the current level of concentration continue, however, consuming contaminated marine products could have an impact on the health."

(Mar. 23, 2011)