Here are some key developments in the worst atomic accident since Chernobyl in 1986:

- March 11, 2011 -

A 9.0-magnitude earthquake strikes off Japan's northeast coast, causing a massive tsunami that destroys entire towns and villages along the Pacific shore, leaving nearly 18,500 people dead or missing.

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 and melt down.

The government issues evacuation orders to residents who live in the immediate vicinity of the plant. The government gradually expands the order.

- March 12, 2011 -

Workers open a reactor vent, releasing pressure and radioactive fumes from inside.

The first of a series of hydrogen explosions at the plant rips through a building casing reactor number one, but the reactor itself remains intact.

Some 160,000 people living near the plant leave their homes.

- March 16, 2011 -

Then-Emperor Akihito makes an emergency television address in a bid to reassure a worried public.

- December 16, 2011 -

Japan says it has tamed the leaking reactors, declaring that they are in a state of cold shutdown.

- June 11, 2012 -

About 1,300 Fukushima residents file a criminal complaint against TEPCO executives and other bodies over the accident, starting a series of legal complaints in connection to the disaster.

- June 20, 2012 -

TEPCO releases an accident report that says the tsunami's strength was beyond what could have reasonably been foreseen.

- July 4, 2012 -

A panel of experts appointed by parliament concludes that the accident was "a profoundly manmade disaster -- that could and should have been foreseen and prevented."

- September 7, 2013 -

Prime Minister Shinzo Abe claims that the Fukushima crisis is "under control" in a speech to the International Olympic Committee.

Tokyo wins its bid to host the 2020 summer Games, as Fukushima plant crews work to contain huge amounts of waste water used to cool the crippled reactors. Decommissioning is expected to take decades.

- September 9, 2013 -

Prosecutors decline to press charges against three former TEPCO executives and other officials, saying there is little chance of winning a conviction.

- July 31, 2015 -

A judicial review panel composed of ordinary citizens rules -- for the second time since the accident -- that the three TEPCO executives should be put on trial. The decision forces prosecutors to proceed with the case.

- March 17, 2017 -

A court for the first time orders the government and TEPCO to pay compensation, ordering a total of 38.6 million yen ($340,000) be paid to residents who fled their homes after the nuclear disaster.

- June 30, 2017 -

Three TEPCO executives plead not guilty to professional negligence resulting in death and injury.

- February 8, 2018 -

A Tokyo court orders TEPCO to pay $10 million in fresh damages to plaintiffs who fled their homes after the disaster, an increase over what the operator had offered in compensation.

- September 19, 2019 -

Tokyo district court acquits three TEPCO executives of professional negligence in the only criminal prosecution stemming from the Fukushima disaster. The men had faced up to five years in prison.

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TEPCO - TOKYO ELECTRIC POWER