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Timeline: Japan's unfolding nuclear crisis

world Updated: Mar 16, 2011 09:27 IST

Reuters
Highlight Story

Japan is under global scrutiny over the handling of its nuclear crisis after a huge earthquake crippled several reactors at a nuclear power complex, raising fears of an uncontrolled radiation leak.

Below is a timeline of statements made by Japanese authorities and the complex's owner, Tokyo Electric Power (TEPCO) , after the quake struck on Friday, the strongest tremor ever recorded in Japan.

Friday, March 11
19:46 - The government reveals a cooling problem at TEPCO's Fukushima Daiichi nuclear plant on the northeast coast, which bore the brunt of the quake and tsunami. Chief cabinet secretary Yukio Edano says the government has declared an emergency as a precaution but he says there is no radioactive leak.

21:34 - TEPCO confirms water levels falling inside reactors at the plant, and says it is trying to avert the exposure of nuclear fuel rods by restoring power to its emergency power system so that it can pump water inside the reactors.

21:49 - Jiji news agency says evacuation area around the plant is extended to 3 km from 2 km and quotes authorities as saying no radioactive leak has been confirmed.

21:55 - The government says radiation has leaked from one of the plant's reactors.

22:45 - Vienna-based International Atomic Energy Agency (IAEA) says Japan advised that a heightened state of alert has been declared but no release of radiation had been detected.

It says Japanese authorities also reported a fire at the Onagawa nuclear power plant, which has since been extinguished.

"They say Onagawa, Fukushima Daini and Tokai nuclear power plants were also shut down automatically, and no radiation release has been detected," the statement says.

Saturday, March 12
00:38 - The World Nuclear Association, the main nuclear industry body, says it understands the situation is under control, and water is being pumped into the reactor's cooling system. An analyst at the association says he understood a back-up battery power system had been brought online after about an hour, and begun pumping water back into the cooling system.

00:40 - US Secretary of State Hillary Clinton says the United States has transported coolant to the stricken nuclear plant. "We just had our Air Force assets in Japan transport some really important coolant to one of the nuclear plants," Clinton says at a meeting of the President's Export Council.

01:27 - Jiji says Fukushima prefecture expects cooling function at the plant to be restored by 1630 GMT (0130 local)

01:46 - Jiji quotes TEPCO as saying pressure inside the No. 1 reactor at the plant has been rising, with the risk of a radiation leak. It plans to take measures to release the pressure, the report says.

02:00 - Kyodo news agency quotes TEPCO as saying pressure inside the No. 1 reactor rose to 1.5 times designed capacity.

03:04 - Japan's nuclear safety watchdog confirms TEPCO is considering steps to lower the pressure in a container in the No. 1 reactor. A spokesman for the Nuclear and Industrial Safety Agency says it is unknown whether radiation levels are high in the container, which is inside a turbine building.

03:13 - Kyodo news agency quotes Japan's trade minister as saying a radiation leak could take place at the plant.

03:14 - Cabinet secretary Edano says TEPCO realises the need to release pressure inside the plant, that this could cause a small radiation leak.

06:37 - US officials say the US military did not provide any coolant for the Japanese nuclear plant, despite Clinton's earlier remarks. They say US Air Force "assets" in Japan delivered coolant to a nuclear plant. One US official says Japan had asked the United States for the coolant but ultimately handled the matter on its own.

07:19 - TEPCO says it has lost its ability to control pressure in some reactors of a second nuclear power plant at its Fukushima facility. Pressure is stable inside the reactors but rising in the containment vessels, a spokesman says, although he did not know if there would be a need to release pressure at the plant at this point, which would involve a release of radiation.

09:34 - Kyodo news agency says Japan has begun evacuating about 20,000 people from vicinity of the nuclear plants.

10:07 - TEPCO has begun releasing pressure from No. 1 reactor at Fukushima Daiichi nuclear plant, the Trade Ministry says. TEPCO says it will prepare for the release of pressure from the second nuclear plant, the Fukushima Daini plant, as pressure mounts. TEPCO and the authorities battle to contain rising pressure at the plants. They say thousands of residents in the area have been evacuated.

17:47 - Cabinet secretary Edano confirms an explosion and radiation leak at Fukushima Daiichi. "We are looking into the cause and the situation and we'll make that public when we have further information," Edano says. "At present, we think 10 km evacuation is appropriate."

20:43 - TEPCO plans to fill the leaking reactor with sea water to cool it and reduce pressure in the unit, Edano says.

"The nuclear reactor is surrounded by a steel reactor container, which is then surrounded by a concrete building," Edano says. "The concrete building collapsed. We found out that the reactor container inside didn't explode."

"We've confirmed that the reactor container was not damaged. The explosion didn't occur inside the reactor container. As such there was no large amount of radiation leakage outside," he adds.

"At this point, there has been no major change to the level of radiation leakage outside (from before and after the explosion), so we'd like everyone to respond calmly."

"We've decided to fill the reactor container with sea water. Trade minister Kaieda has instructed us to do so. By doing
this, we will use boric acid to prevent criticality."

Edano says it will take about five to 10 hours to fill the reactor core with sea water and around 10 days to complete the process. He says due to the falling cooling-water level, hydrogen was generated and leaked into a space between the building and the container. It mixed with oxygen and exploded.

22:21 - The IAEA quotes Japanese authorities as saying they are preparing to distribute iodine to people living near the stricken nuclear power complex. Iodine can be used to help protect the body from radioactive poisoning.

Sunday, March 13
00:49 - A nuclear accident in Japan on Saturday rates as less serious than both the Three Mile Island accident in 1979 and the 1986 Chernobyl nuclear disaster, Japan's nuclear safety agency said. An official at the agency said it has rated the incident at 4 under the International Nuclear and Radiological Event Scale. Three Mile Island was rated 5 while Chernobyl was rated 7 on the 1 to 7 scale, the official said.

05:41 - In a 20-km radius around the Fukushima Daiichi complex, an estimated 110,000 people have been evacuated, the IAEA says. In a 10-km radius around the nearby Fukushima Daini complex, about 30,000 people have been evacuated.

06:20 - The number of individuals exposed to radiation from the Fukushima Daiichi complex could reach as high as 160, an official of the Japan Nuclear and Industrial Safety Agency.

10:38 - Kyodo quotes TEPCO as saying radiation levels have risen above safe limits around the complex and that the firm has
informed the government of an "emergency situation". It did not mean an immediate threat to human health, TEPCO says.

15:23 - Chief cabinet secretary Edano says there is a risk of an explosion at a building housing at the Fukushima Daiichi complex where an explosion on Saturday blew off the roof off another reactor building.

23:37 - Jiji quotes TEPCO as saying it is preparing to put sea water into the No.2 reactor at its Fukushima Daiichi nuclear power plant.