Key events since 2011

Here is a timeline of key events related to the accident.

2011

March 11: A magnitude-9.0 earthquake strikes off the coast of northeastern Japan, triggering a towering tsunami that smashes into the Fukushima Daiichi Nuclear Power Plant, knocking out power and cooling systems and triggering meltdowns in three reactors.

March 12: A hydrogen explosion occurs at the plant's No 1 reactor, sending radiation into the air. Residents within a 20-kilometer radius are ordered to evacuate.

April 4: Engineers release more than 10,000 metric tons of nuclear-contaminated water into the sea — about 100 times more radioactive than legal limits — that had been used to cool overheated fuel rods after running out of storage capacity, affecting fish and angering local fishing groups.

Dec 16: Japan says damaged reactors are in stable state of "cold shutdown".

2012

July 23: A government-appointed independent investigation concludes that the nuclear accident was caused by a lack of adequate safety and crisis management by the plant's operator, Tokyo Electric Power Company, lax oversight by nuclear regulators and collusion.

2013

July 22: TEPCO says nuclear-contaminated water has continued to leak from the plant into groundwater, making it radioactive.

2015

Aug 25: The government and TEPCO issue a statement to Fukushima fisheries groups pledging to never release contaminated water into the sea without their "understanding".

2018

Oct 1: TEPCO says water treated at the Fukushima site still contains radioactive materials, and apologizes to the government after previously insisting the materials had been removed. About a million tons of water is stored at the plant, enough to fill about 500 Olympic-size swimming pools.

2020

Feb 10: As the amount of leaked radioactive cooling water stored in tanks at the plant rapidly increases, a government panel recommends its controlled release into the sea. TEPCO says its 1.37-million-ton storage capacity will be reached in the first half of 2024.

2021

April 13: The government announces plans to release nuclear-contaminated water into the Pacific Ocean, drawing neighbors' ire. Local fishers also oppose the plan.

2023

Aug 22: Prime Minister Fumio Kishida, after visiting the plant to highlight the safety of the release plan and pledging long-term support for fisheries groups, announces the discharge will begin as early as Thursday if weather and sea conditions allow.

Aug 24: Fukushima Daiichi Nuclear Power Plant begins releasing its first batch of nuclear-contaminated water into the Pacific Ocean.

Agencies via Xinhua