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Japan's tsunami and nuclear disaster: a timeline
by Staff Writers
Tokyo (AFP) Dec 16, 2011

Here are key developments in Japan as the country prepares to announce the cold shutdown of stricken reactors at its Fukushima nuclear plant, nine months after a massive quake and tsunami triggered the worst atomic accident since Chernobyl in Ukraine in 1986.

- March 11, 2011: A 9.0-magnitude earthquake, the world's fourth largest since 1900, strikes off Japan's northeast coast, triggering a massive tsunami that destroys entire towns and villages along the Pacific coast and kills about 20,000 people.

The power supply and reactor cooling systems at the coastal Fukushima Daiichi nuclear power plant about 220 kilometres (135 miles) northeast of Tokyo are damaged, causing fuel inside to overheat.

- March 12: The government orders the evacuation of residents living near the plant, where an explosion rips through a reactor building.

- March 14: A second explosion hits the plant.

- March 15: Two more blasts and a fire rock the plant, and radiation levels reach dangerous levels.

- April 1: Japan announces start of the "rehabilitation and reconstruction phase".

- April 4: Operations start to dump 11,500 tonnes of radioactive water into the Pacific amid continued emergency cooling operations.

- April 7: Four people are killed and 140 injured in a new 7.1 magnitude quake in the northeast, one of more than 500 strong aftershocks so far.

- April 12: Japan upgrades its assessment of the severity of the nuclear emergency to a maximum seven on an international scale -- equal with Chernobyl, although less radiation was released.

- April 22: Japan approves an initial disaster recovery budget of four trillion yen ($49 billion).

- May 5: Nuclear plant workers enter a Fukushima reactor building for the first time since the explosion.

- May 6: Japan's government decides to ask another nuclear plant operator to shut two reactors at the quake-prone Hamaoka plant southwest of Tokyo.

- May 11: Emperor Akihito visits evacuees from the radiation zone.

- May 19: Data shows Japan's economy plunged back into recession in the first quarter because of the impact of the disaster.

- May 26: Prime Minister Naoto Kan says Japan will boost its share of green energy to 20 percent of total power supply by 2020 and review from scratch plans for any new reactors.

- May 27: Fitch Ratings agency revises its debt outlook for Japan to negative from stable.

- June 7: Japan more than doubles its initial estimate of radiation released from the Fukushima nuclear plant in the week after the tsunami.

- July 5: Japan's cabinet approves a second special disaster recovery budget of two trillion yen ($24 billion).

- Disaster reconstruction minister Ryu Matsumoto quits after causing a furore with scathing remarks to leaders of tsunami-hit regions.

- July 19: Japan bans all cattle shipments from Fukushima prefecture over radiation fears.

- July 28: Japan widens its ban on beef from the disaster zone.

- August 4: The government says it will fire three top energy officials over their handling of the disaster.

- August 8: UN chief Ban Ki-moon visits the area close to the plant.

- August 18: Tests find traces of radioactive elements in the thyroid glands of 45 percent of children from the region around the stricken plant, but they are not present at dangerous levels.

- August 25: Japan lifts a ban on beef from disaster-hit regions.

- August 26: Kan resigns after just 15 months in office following criticism of his leadership in the aftermath of the twin disasters.

- August 30: Kan's finance minister Yoshihiko Noda becomes Japan's sixth new prime minister in five years.

- September 10: The minister for economy, industry and trade is forced to quit after describing the Fukushima evacuation zone as a "town of death".

- September 13: Noda vows to reduce atomic power use.

- September 19: Tens of thousands of people rally in Tokyo calling for an end to nuclear energy in Japan.

- September 30: Japan lifts evacuation advisories for five areas near the crippled plant.

- October 6: A worker at the stricken Fukushima nuclear power plant dies. It is unclear whether his illness was related to radioactive leaks.

- November 2: Plant operator Tokyo Electric Power (TEPCO) says it fears that nuclear fission has resumed inside one of the Fukushima reactors.

- November 4: TEPCO says it expects a net loss of 576.3 billion yen ($7.4 billion) for the fiscal year to March 2012.

- Japan agrees to give TEPCO $11.5 billion to help it pay compensation to those affected by the disaster.

- November 15: The UN atomic agency praises Japan's clean-up efforts but says there is still room for improvement.

-- Scientists warn that land in parts of Japan is no longer safe to farm because of high levels of radiation in the soil.

- November 16: Japan announces its first ban on rice produced near the crippled plant after samples showed radioactive contamination well above legal limits.

- November 21: Parliament passes a third extra recovery budget of 12.1 trillion yen ($157 billion).

- December 6: TEPCO says that highly radioactive water has leaked into the Pacific, and promises to prevent similar incidents.

- Radiation contamination has been found in a leading brand of Japanese baby formula, its manufacturer says.

- December 9: The former chief of the crippled plant has cancer of the esophagus, the operator says, but adds it is unlikely to be linked to radiation.

- December 16: Japan looks set to announce it has finally tamed the leaking reactors with the declaration they are in a state of cold shutdown after nine months.

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Key steps to Fukushima plant 'cold shutdown'
Tokyo (AFP) Dec 16, 2011 - Japan's announcement that crippled reactors at its Fukushima nuclear plant have been brought to a state of cold shutdown marks the second step in the government's recovery plan and is the culmination of nine months of sometimes chaotic efforts to bring the reactors under control.

Authorities have long flagged the move as vital to clean-up efforts.

The disaster erupted on March 11, when waves triggered by a magnitude-9.0 earthquake swamped the reactors' cooling systems, sparking meltdowns, explosions and the release of radioactive material in the world's worst nuclear accident since Chernobyl in 1986.

An initial key challenge was how to inject water into the reactors to cool melting fuel inside and then how to deal with the massive amounts of contaminated liquid that accumulated as a result of those emergency efforts.

With no power supply to pump water in, military helicopters were used to dump water from above while firefighters sprayed water from high-pressure hoses.

Within weeks of the disaster, plant operator Tokyo Electric Power Co. (TEPCO) was forced to discharge more than 10,000 tonnes of low-level radioactive water into the Pacific from the plant, located some 220 kilometres (135 miles) northeast of Tokyo.

The release provoked outrage among fishermen as far afield as China, who fretted their catch would be contaminated.

TEPCO subsequently built massive water tanks at the plant to store the runoff and rented a "mega-float" ocean tanker from Mitsubishi Heavy Industries.

Another initial focus was on injecting nitrogen into the reactors in a bid to prevent a repeat of the hydrogen explosions that had torn reactor housing units apart and worsened the release of radiation into the atmosphere.

In mid-July, the government and TEPCO said they had met three-month goals, including installing systems that remove radioactive substances from the polluted water before recycling the decontaminated liquid to further cool reactors.

"A turning point was to have successfully established a circulation system for cooling water," said Kazuhiko Kudo, a nuclear reactor expert and professor at Kyushu University in Fukuoka.

"But the circulation system is not a proper one for nuclear reactors and is still a stop-gap measure," Kudo said.

"The system in Fukushima, which is placed outside the reactor and connected with long pipes, is quite unstable," he added. "It is necessary to further improve the system as quickly as possible."

With ongoing fears of high radiation levels, workers have since battled to maintain the cooling system so that reactor water temperatures remain below 100 degrees centigrade (212 Fahrenheit) -- a condition necessary for Friday's "cold shutdown" declaration.

One of the major challenges TEPCO will face in the longer term is the removal of spent fuel from containment vessels.

"Removing fuel is quite challenging as the status of the fuel rods has yet to be confirmed," Kudo said.

One option under consideration is the possible covering of reactors with outer shells, a measure technicians hope will prevent further radioactive release.

The construction of wave barriers to guard against the effects of another tsunami in geologically unstable Japan is also a key priority, as is the containment -- and eventual disposal -- of contaminated water.

"Cooling water itself is still seeping out through cracks into underground water, which is eventually leaking into the sea," said Tetsunari Iida, director of the Institute for Sustainable Energy Policies, an anti-nuclear body.

"We now need to worry about different isotopes, such as strontium, which are more water soluble and could contaminate the marine food chain," he said.


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Merging Tsunami Doubled Japan Destruction
Pasadena CA (JPL) Dec 08, 2011
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