Events at Fukushima Daiichi nuclear plant since the 2011 earthquake, tsunami and nuclear disaster

abcnews.go.com:

The operator of the wrecked Fukushima Daiichi nuclear power plant is now releasing treated but still slightly radioactive wastewater into the Pacific Ocean

Treated but still slightly radioactive wastewater from the wrecked Fukushima Daiichi nuclear power plant is being released into the Pacific Ocean in a process that began Thursday — more than 12 years after a massive earthquake and tsunami caused the meltdowns of three of its reactors and the continuing leakage of cooling water. Here is a timeline of events:

— March 11, 2011: A magnitude 9.0 earthquake strikes off the coast of northeastern Japan, triggering a towering tsunami that smashed into the Fukushima nuclear plant, knocking out power and cooling systems and triggering meltdowns in three reactors.

— March 12, 2011: A hydrogen explosion occurs at the plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at the two other damaged reactors over the following days.

— April 4, 2011: The plant operator releases more than 10,000 tons of low-level radioactive water into the sea to empty a storage facility so it can be used to hold more highly contaminated water, affecting fish and angering local fishing groups.

— April 12, 2011: Japan raises the accident to category 7, the highest level on the International Nuclear and Radiological Event Scale, from an earlier 5, based on radiation released into the atmosphere.

— Dec. 16, 2011: After months of struggle to stabilize the plant, Japan declares a “cold shutdown,” with core temperatures and pressures down to a level where nuclear chain reactions do not occur.

— July 23, 2012: A government-appointed independent investigation