Timeline: Cleaning up the Fukushima disaster

The Fukushima Daiichi plant was devastated by a tsunami in 2011, but Japan’s efforts to clean up have been mired in controversy.

Workers in blue overalls, hard hats and masks in Fukushima. Behind them are the tanks contained the treated radioactive water
The water used to cool the fuel rods has been stored on site in giant tanks [File: Issei Kato/Reuters]

Japan has started releasing treated radioactive water from its crippled Fukushima nuclear power plant into the Pacific Ocean, a milestone in its challenging decommissioning process.

Here is a timeline of key events related to the Fukushima disaster and Japan’s efforts to clean up the site and close down the plant.


March 11

A magnitude 9 earthquake off the coast of northeastern Japan triggers a devastating tsunami that knocks out power and cooling systems at Tokyo Electric Power Co’s (TEPCO) Fukushima Daiichi plant, leading to the meltdown of three of its six reactors.

The government declares a nuclear emergency.

March 12

A hydrogen explosion occurs at the plant’s reactor number one, releasing radiation into the air, and residents within a 20km (12-mile) radius are ordered to evacuate. Similar explosions occur at the two other damaged reactors over the following days.

TEPCO, meanwhile, begins using seawater to cool the reactors’ fuel rods.

April 4

After running out of storage capacity for the water used to cool the overheated fuel rods, engineers release more than 10,000 tonnes of the heavily contaminated water – about 100 times more radioactive than legal limits – into the Pacific, affecting fish and angering local fishing groups.

April 12

Japan raises the accident to category 7, the highest level on the International Nuclear and Radiological Event Scale, from category 5, based on radiation released into the atmosphere.

December 16

Japan announces Fukushima’s damaged reactors are in a stable state of “cold shutdown”.


July 23

A government-appointed independent investigation concludes that the nuclear accident was caused by a lack of adequate safety and crisis management by TEPCO, lax oversight by nuclear regulators and collusion.


March 30

An Advanced Liquid Processing System (ALPS) begins operating to improve the treatment of contaminated water.

July 22

TEPCO says radioactive water continued to leak from the plant into groundwater, making it radioactive, with implications for drinking water and the Pacific Ocean.


April 1

Residents begin to return to the exclusion zone around Fukushima as decontamination of the area is completed.

December 22

The company completes the removal of spent nuclear fuel rods from the cooling pool of reactor number four, an initial milestone in a decommissioning process that is expected to take years.


March 31

TEPCO introduces an underground wall that is cooled to freezing temperatures around four reactor buildings as a way of reducing the amount of groundwater seeping into reactor basements and mixing with the highly radioactive cooling water leaking from the melted reactors.


October 1

TEPCO says water treated at the Fukushima site still contains radioactive materials and apologises to the government after previously insisting the materials had been removed. About 1 million tonnes of water are now stored at the plant, enough to fill about 500 Olympic swimming pools.

IAEA chief Rafael Grossi handing the report on the Fukushima water release plan to Japanese Prime Minister Fumio Kishida. The report is blue. There is a Japanese flag behind them.
IAEA chief Rafael Grossi visited Fukushima in July 2023, with the agency later giving its approval to the discharge plan [File: Eugene Hoshiko/Pool via Reuters]

November 13

The International Atomic Energy Agency (IAEA), the United Nations’ nuclear watchdog, says Japan must urgently tackle the build-up of contaminated water.

April 13

Japan says it has decided to release the water into the sea, drawing anger from China, which calls the move “extremely irresponsible”, as well as South Korea, which summons the Japanese ambassador. Local fishermen also make clear their opposition to the plan.


February 10

A government panel recommends the contaminated water’s controlled release into the sea. TEPCO says the site will reach the limit of its storage capacity of 1.37 million tonnes in the first half of 2024.


December 28

Japan maps out a plan for the water release that includes compensation standards for local industry and the compilation of a safety report.

Workers in Fukushima prefecture sort through the catch. A woman in red overalls is holding a large fish while someone else points at a blue container
Fishing communities in Fukushima worry about the impact of the discharge on their industry [File: Kyodo via Reuters]


July 4

Japan secures approval for the water release from the IAEA following a two-year review and a visit to the site by its chief Rafael Grossi. IAEA says the Japanese plans are consistent with global safety standards and would have “negligible radiological impact” on people and the environment.

July 7 

Citing its own assessment and review of evidence, South Korea says it believes the water release will be safe if carried out as detailed in the proposal.

August 22

Japanese Prime Minister Fumio Kishida, after visiting the plant to highlight the safety of the water release plan and pledging long-term support for fisheries groups, announces the discharge will begin in 48 hours if weather and sea conditions allow. The announcement leads to strong condemnation from China and concern among the fisheries industry.

August 24

TEPCO announces the release of the water has begun. At protests in Seoul, at least 14 people are detained after they try to break into the Japanese embassy.

Condemning Japan’s decision to go ahead with the discharge, China announces the suspension of all imports of aquatic products from Japan.

Interactive_Fukushima_waste water_map

Source: Al Jazeera and news agencies