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At 2:46 PM, a 9.0 magnitude earthquake strikes off Honshu island. Reactors 1,2 and 3 at the Fukushima Daiichi plant automatically shut down, and reactors 4,5,and 6 were already offline for maintenance at the time. Plant was initially being cooled by backup generators.
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Emergency backup battery for reactor 3 runs out and the fuel rods are exposed. Some steam is released into the air. As the situation in the 3 reactors worsens, the evacuation zone is extended.
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A major explosion in the building for reactor 3 damages the coding system for reactor 2, triggering core damage in that unit. The INES (International Nuclear Event Scale) level for the situation is escalated to 5 and there's talk of raising it to 6.
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An explosion severely damages reactor 4. Another explosion takes place in unit 3. A fire starts in unit 4. Radiation near reactor 3 measured at 400 millisieverts per hour).
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A breach in reactor 3's containment vessel is suspected. US Navy sends a barge with 500,000 gallons of fresh water to the scene. Voluntary evacuation zone is extended to a radius of 19 miles.
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Two missing working are found dead, apparently from injuries in the Tsunami
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TEPCO begins dumping radioactive water from storage tanks into the Pacific
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The INES level of the incident is raised to 7 - the same level as Chernobyl. It is determined by nuclear experts to be most complicated accidents of its kind ever to occur
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Since the old TEPCO president resigned, a trial of a new treatment program for the radioactive water begins.
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Contaminated water is no longer being generated. Recycled water is being used for cooling.
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The US Nuclear Regulatory Commission confirms that the reactors are now stable - some 9 months after the initial accident.
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The Japanese government further narrowed the size of the evacuation zone around the disaster site, allowing 275 people in 139 households to return to their homes. It is unclear whether they will actually do so, due to living conditions in the area.
