全国の水道の放射能濃度

Workers engaged in operations to stabilize the crippled Fukushima Daiichi Nuclear Power plant take a rest on the floor of a gymnasium inside the grounds of the Fukushima Daini Nuclear Power Plant, about 10km away from the crippled Daiichi plant in Fukushima prefecture, northern Japan, in this photo taken May 7, 2011 and released June 2, 2011 by industrial medical doctor Takeshi Tanigawa, who examined the workers.
REUTERS/Takeshi Tanigawa/Handout/Files

Reuters - By Kevin Krolicki and Chisa Fujioka - June 24, 2011

A decade and a half before it blew apart in a hydrogen blast that punctuated the worst nuclear accident since Chernobyl, the No. 3 reactor at the Fukushima nuclear power plant was the scene of an earlier safety crisis.

Then, as now, a small army of transient workers was put to work to try to stem the damage at the oldest nuclear reactor run by Japan's largest utility.

The Financial Times - By Jonathan Soble in Tokyo - June 23, 2011

About 110,000 tonnes of highly contaminated water have accumulated in basements and service tunnels under the plant’s four crippled reactors, a result of three months’ worth of emergency cooling efforts since the March 11 tsunami. The onset of Japan’s early-summer rainy season has made the situation more critical by adding to the build-up.

The Japan Times - June 21, 2011

Tokyo Electric Power Co. continued struggling Monday to restart a newly installed water treatment system at its crippled Fukushima No. 1 nuclear plant, aiming to resume full operations Tuesday.

The treatment system is designed to remove highly radioactive materials from the massive amounts of water accumulating at the plant, thus its full operation is vital for efforts to contain the three-month-old nuclear crisis, because Tepco hopes to eventually recycle the water to cool the plant's damaged reactors.

But the new system was halted at 12:54 a.m. Saturday, after becoming fully operational at 8 p.m. Friday, because the radiation level of a component to absorb cesium had reached its limit and required replacement much earlier than expected, Tepco officials said.

Tepco has been trying to ascertain why the component didn't work as hoped and is probing ways to solve the problem, company officials said.

Tepco meanwhile said Monday it fully opened the doors of the reactor 2 building to lower the humidity inside so workers can enter the site, and denied this would have a negative impact on the environment.

The Yomiuri Shimbun - Daily Yomiuri Online - Associated Press - June 9, 2011

In a report submitted to the International Atomic Energy Agency, the government has called for a drastic revision of nuclear reactor design standards, including the development of air-cooling devices and a reconsideration of the location of temporary storage pools for spent nuclear fuel rods.

The report concerning the accident at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant following the March 11 earthquake and tsunami was submitted to the IAEA on Tuesday.

The report included 28 proposals to strengthen the safety of nuclear plants, drawing on lessons from this year's earthquake-triggered nuclear crisis.

The Economy, Trade and Industry Ministry's Nuclear and Industrial Safety Agency (NISA) the same day instructed electrical utility companies that operate nuclear power plants to take emergency measures to prevent hydrogen explosions and secure sufficient equipment to measure radiation levels.

The report may significantly affect the operations of about 50 nuclear reactors in the nation, observers said.

In this May 27, 2011 photo released by the International Atomic Energy Agency, or IAEA, members of the IAEA fact-finding team in Japan visit the Fukushima Dai-ichi nuclear plant in Okuma, Fukushima prefecture, northern Japan. (AP Photo/IAEA)

Reuters - June 1, 2011

TOKYO, June 1 (Reuters) - Japan underestimated the risk of tsunamis and needs to closely monitor public and workers' health after the crisis at the Fukushima Daiichi nuclear plant, a team of international safety inspectors said in a preliminary review of the world's worst nuclear disaster since Chernobyl.

The report, from an International Atomic Energy Agency (IAEA) team led by Britain's top nuclear safety official Mike Weightman, highlighted some of the well-documented weaknesses that contributed to the crisis at Fukushima when the plant, 240 km (150 miles) north of Tokyo, was hit by a massive earthquake and then a tsunami in quick succession on March 11.

Those start with a failure to plan for a tsunami that would overrun the 5.7-metre (19 ft) break wall at Fukushima and knock out back-up electric generators to four reactors, despite multiple forecasts from a government agency and operator Tokyo Electric Power Co's own scientists that such a risk was looming.

The New York Times - March 17, 2011

Nearly 25 years after the accident at the Chernobyl nuclear power plant in Ukraine, children and teenagers who drank contaminated milk or ate affected cheese in the days and weeks after the explosion still suffer from an increased risk of thyroid cancer, according to a study released Thursday by the National Cancer Institute.

World Health Organization - Fact sheet N° 303 - April 2006

Background

On 26 April 1986, explosions at reactor number four of the nuclear power plant at Chernobyl in Ukraine, a Republic of the former Soviet Union at that time, led to huge releases of radioactive materials into the atmosphere. These materials were deposited mainly over countries in Europe, but especially over large areas of Belarus, the Russian Federation and Ukraine.

An estimated 350 000 clean-up workers or "liquidators" from the army, power plant staff, local police and fire services were initially involved in containing and cleaning up the radioactive debris during 1986-1987. About 240 000 liquidators received the highest radiation doses while conducting major mitigation activities within the 30 km zone around the reactor. Later, the number of registered liquidators rose to 600 000, although only a small fraction of these were exposed to high levels of radiation.

In the spring and summer of 1986, 116 000 people were evacuated from the area surrounding the Chernobyl reactor to non-contaminated areas. Another 230 000 people were relocated in subsequent years.

By YURI KAGEYAMA and JUSTIN PRITCHARD, Associated Press 

TOKYO – Japanese nuclear regulators trusted that the reactors at the Fukushima Dai-ichi complex were safe from the worst waves an earthquake could muster based on a single-page memo from the plant operator nearly a decade ago. In the Dec. 19, 2001, document — one double-sized page obtained by The Associated Press under Japan's public records law — Tokyo Electric Power Co. rules out the possibility of a tsunami large enough to knock the plant offline and gives scant details to justify this conclusion, which proved to be wildly optimistic.

May 17, 2011

The International Atomic Energy Agency will dispatch an international expert fact-finding mission to Japan.

Based upon the agreement between the IAEA and the Government of Japan, the mission, comprising nearly 20 international and IAEA experts from a dozen countries, will visit Japan between 24 May and 2 June 2011. Under the leadership of Mr. Mike Weightman, HM Chief Inspector of Nuclear Installations of the United Kingdom, the mission will conduct fact-finding activities at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Station (NPS) site and in other locations.

The expert mission will make a preliminary assessment of the safety issues linked with TEPCO's Fukushima Dai-ichi NPS accident following the Great East Japan Earthquake and Tsunami. During the mission, areas that need further exploration or assessment based on the IAEA safety standards will also be identified.

In the course of the IAEA mission, the international experts will become acquainted with the Japanese lessons learned from the accident and will share their experience and expertise in their fields of competence with the Japanese authorities.

Time - May 24, 2011

Two weeks after announcing the meltdown of fuel inside Fukushima's No. 1 reactor, Tokyo Electric Power Company (TEPCO) has said there have very likely been partial meltdowns at the other two reactors that were operating when the crisis began on March 11 as well. A spokesman for TEPCO, Japan's largest power company that has come under fire for its management of the crippled plant, said fuel rods at reactor No. 3 started melting March 13, two days after the 9.0 earthquake and ensuing tsunami struck the plant. Fuel rods at No. 2 probably started melting a day later, on March 14.

JapanToday.com - May 24, 2011

TOKYO —

The operator of the troubled Fukushima Daiichi nuclear power complex said Tuesday that meltdowns are assumed to have occurred in the cores of the Nos. 2 and 3 reactors in addition to the meltdown already confirmed at the No. 1 reactor, but stressed that it believes the melted fuel is being kept cool at the bottom of the pressure vessels.

Tokyo Electric Power Co also maintained its view that it was only after the giant tsunami hit after the devastating March 11 earthquake that the plant lost all its power sources, eventually leading to the loss of the reactors’ key cooling functions.

The announcement came as the utility is proceeding with work to assess data taken shortly after the nuclear accident occurred. Industry minister Banri Kaieda said the government agreed at a cabinet meeting Tuesday to set up a third-party panel to look into the causes of the country’s worst ever nuclear crisis.

The government has tapped Yotaro Hatamura, a 70-year-old professor emeritus at the University of Tokyo, as head of the special panel, Deputy Chief Cabinet Secretary Yoshito Sengoku said in a press conference.