Frances Mao
BBC News

We're going to leave our live coverage of the Fukushima water release here for now, thanks for following along.

• If you want to keep reading about the science and politics of this complex story, head to our main news story
• This explainer is also helpful

Today's page was written by Nicholas Yong, Tiffanie Turnbull, Kelly Ng, Yvette Tan and Sam Hancock - with contributions from our reporters across Japan, South Korea, China and Singapore.

It was edited by Ayeshea Perera and myself.

What happened today?

Twelve years after the nuclear disaster at Fukushima, Japan began releasing some of the contaminated water from the plant into the Pacific Ocean.

Despite widespread opposition, the government and plant operators Tepco went ahead with the plan - carefully vetted by the UN atomic regulator.

Why?

Japan used water to cool the plant's reactors when it went into meltdown in 2011 - and this highly radioactive water was then treated and collected in tanks every day. But the site was running out of storage space.

Image source, Reuters

How was the water made safe?

It was treated to remove all radioactive elements, except tritium which is very difficult to remove. The water was diluted to reduce radioactivity to 1,500 becquerels per litre, far below the drinking water standard of 10,000 Bq/L.

How did it go down?

There were citizen protests in Japan and South Korea, but China's government came out swinging - labelling Japan as "selfish" and "irresponsible". It also imposed a ban on all seafood from Japan.

What happens next?

Thursday's release was the first of four scheduled between now and the end of March 2024. The entire process will take at least 30 years.

Tokyo Electric Power Company, known as Tepco, owns the Fukushima Daiichi nuclear plant which suffered a nuclear meltdown after it was damaged by the earthquake and tsunami in March 2011.

Tepco is the fourth-largest power company in the world, supplying about one-third of Japan's electricity in the biggest cities.

It has faced billions of dollars in compensation claims since the disaster - with bankruptcy fears forcing the government to take control in 2012.

In 2014 they were sued by Fukushima workers over unpaid hazard pay. Two years later, Tepco admitted it should have announced sooner there was a nuclear meltdown at the site.

Last year, former executives were ordered to pay 13 trillion yen ($89bn) for failing to prevent the disaster.

Yuna Ku
BBC Korean Service

A legal group has filed a petition to South Korea’s Constitutional Court to stop the release of Fukushima water – on behalf of more than 40,000 people and 160 whales.

Kim Young-hee of the Lawyers for a Democratic Society argues the South Korean government’s reaction to the release is unconstitutional as it fails to protect the rights of citizens.

The whales are listed as petitioners because they're identifiable and their survival is at stake, Ms Kim said.

Usually, it takes five years for South Korea’s top court to rule on such cases. However, she said the case was worth pursuing because the water release is to continue for 30 years.

Last week, a court in the Korean city of Busan dismissed a case filed by more than 160 groups against Fukushima's operators because it was beyond its jurisdiction.

In its latest statement, the UN's atomic watchdog said the tritium concentration in the Fukushima water release is well below the "operational limit".

Tritium is a radioactive isotope of hydrogen - the most common form of it is titrated water, which can be found in water all over the world.

The International Atomic Energy Agency (IAEA) - which has a permanent office at Fukushima- said an "independent, on-site analysis" had shown that the tritium concentration in the water discharged was "far below the operational limit of 1,500 becquerels per litre".

The limit is 40 times lower than the Japanese national safety standard for tritium levels in water - and around seven times lower than the limit set by the World Health Organization for drinking water (10,000 becquerels per litre).

Jean Mackenzie
Seoul correspondent

The Fukushima issue has been fiercely politicised in South Korea, as is often the case for matters concerning Japan.

The government has all but endorsed the release of the water, while the opposition is fiercely against it.

In recent weeks there have been protesters out on the streets, while the government held press conferences and made YouTube videos to try to convince the public that the water being discharged is safe.

Over the past year, President Yoon Suk Yeol has made considerable progress with his attempts to improve the country’s strained relationship with Japan. Last week’s summit between Yoon, Japan’s Prime Minister Fumio Kishida and US President Joe Biden was proof of that.

Yoon does not want all his hard work undone over this.

The opposition claims Yoon has compromised people’s health for the sake of this relationship. But the government says the opposition are scaremongering to win votes ahead of next year’s election.

Image source, Reuters

We've had a lot of reaction from Japan's closest neighbours, but people on the other end of the Pacific Ocean are nervous too.

As recently as June, the Pacific Island Forum (PIF) was outspoken in their opposition to Japan's plan to release the treated radioactive water.

But now PIF chair and Cook Islands PM Mark Brown says he believes it "meets international safety standards". A UN regulator delegation recently visited some of the concerned Pacific nations.

Mr Brown said all nations across the region may not agree on the "complex" issue, but he urged them to "assess the science".

Image source, Reuters

After two years of its own checks, the International Atomic Energy Agency (IAEA) greenlit Japan's discharge plan in July.

The agency deployed its own specialist taskforce made up of nuclear safety experts from eleven countries to Fukushima.

In its final report, external it said Japan's water treatment and discharge plan met all international safety standards.

Mariko Oi
Asia Business Correspondent

Today's water release just shows the ongoing impact of the 2011 Fukushima meltdown - the world's worst nuclear disaster since Chernobyl.

Today, just over 7% of Japan’s electric power is generated by nuclear energy. But before 2011, the figure stood at 30%.

The Fukushima disaster prompted anti-nuclear protests across the country and the government halted all nuclear power plants.

The move resulted in a rise in electricity prices with the then boss of Tepco, which owns the Fukushima power plant, warning of further hikes.

Nuclear energy remains a deeply divisive topic but the public sentiment has started to shift and many lawmakers are now pushing to restart the rest of Japan's nuclear power plants.

It coincides with Japan’s aim to be carbon neutral by 2050 because as of now, Japan still relies heavily on fossil fuels such as oil, coal and liquefied natural gas, most of which are imported from overseas and vulnerable to market price changes.

Kelly Ng
BBC News, Singapore

Image source, Global Times

Fear and anger has intensified on Chinese social media, with Twitter-like platform Weibo publishing new posts on the move by the second.

Some users worry that eating seafoood could harm even future generations.

"Why isn't the world concerned about the release of radioactive water into the oceans? This isn't just a question of whether seafood is safe to eat. The circulation of currents means this will affect the whole world," one comment read.

China is known for censoring social media posts which don't align with the state's position.

A Weibo poll for reactions on Tokyo's move included just these options:

• It violates international consensus and maritime protection laws
• It is against common sense and human nature
• It damages the environment

Our Beijing correspondent earlier explained how China has tried to characterise the discharge as a uniquely Japanese act- despite itself being a nuclear power.

Jean Mackenzie
Seoul correspondent

Fishermen in South Korea have long been opposed to release of the water, not because they thought it was unsafe, but because they worried people here would stop buying their fish.

After the disaster in 2011, South Korea banned the sale of seafood from around Fukushima. The fisherman here feared that once the water was released into the ocean, and free to make its way into South Korea’s seas, their catch would also be tainted.

In a survey last month almost two thirds of people said they would eat less seafood or no seafood at all if the water was released.

Now the fishermen’s fear has become a reality - they are urging the government to support them financially.

The authorities have promised to monitor the water closely. It will test local seafood for radiation every day, and test water in real time from more than 200 locations.

BBC News Chinese

Image source, BBC News Chinese

As Hong Kong declared a ban yesterday on seafood imports from 10 prefectures in Japan, sushi lovers in the Chinese territory grabbed their "last chance" to taste the freshly delivered raw fish slices, or sashimi.

Hong Kong, Japan's second biggest seafood market after mainland China, bought 75.5bn yen (US$520m; £409m) worth of seafood from Japan last year.

The BBC spoke to diners concerned about the Fukushima discharge but who did not agree with the ban.

Image source, BBC News Chinese

Image source, BBC News Chinese

Tessa Wong
Asia Digital Reporter

Many scientists have backed Japan’s plan, saying it is sound.

We’ve heard earlier from nuclear chemistry experts and molecular pathologists who stress that the discharged water will not make the sea much more radioactive than it already is – and in the first place, that threat to humans is very, very small.

But it is also worth noting that there is some disquiet in the science and environment community.

Some marine biologists and ocean experts, for example, have argued that more studies need to be done on how 30 years of continued discharge would affect the ocean bed and marine life.

The US National Association of Marine Laboratories released a statement in December saying they were not convinced by Japan’s data., external

"We've seen an inadequate radiological, ecological impact assessment that makes us very concerned that Japan would not only be unable to detect what's getting into the water, sediment and organisms, but if it does, there is no recourse to remove it... there's no way to get the genie back in the bottle," marine biologist Robert Richmond from the University of Hawaii told the BBC earlier this year.

The waste water being released from Fukushima has been treated to have 64 radioactive elements removed - except tritium, a radioactive isotope of hydrogen, which is very difficult to remove from water.

It's an element found in many places- as you can see below.

In the post below, a South Korean diver told the BBC she was worried about drinking the water.

But even if you tried to drink excessive amounts of the seawaters from the Pacific Ocean, the radiation dose would be insignificant, says molecular pathology expert Prof Gerry Thomas.

Japan’s nuclear wastewater has been treated so the level of tritium - the element people are worried about - has been diluted to 1,500 becquerel per litre. A becquerel is a unit of radioactivity.

That is seven times less than the benchmark set by the World Health Organization for safe drinking water - and that is before the wastewater is diluted further by the ocean.

“The water released will be a drop in the ocean, both in terms of volume and radioactivity,” Thomas says.

“There is no evidence that these extremely low levels of radioisotopes have a detrimental health effect.”

And anyway, humans can't drink large amounts of seawater - because it's too salty and our bodies can't process it.

Yuna Ku
BBC Korean Service

Image source, Lawyers for a Democratic Society

Some of the more than 3,000 traditional female divers known as “haenyeo” on South Korea’s picturesque Jeju Island are anxious about the release of the Fukushima water.

Jeju haenyeo dive deep into the sea to gather shellfish and seaweed. They don’t use oxygen masks, their sole protection consists of a rubber suit and goggles and they only work about 90 days a year when the water is warm enough.

“Now I feel it’s unsafe to dive in,” says Kim Eun-ah, who has been doing this job for six years.

Even though scientists says today's release of water is safe and the radiation amounts smaller that what the ocean naturally contains, many people have the wrong impression.

Ms Kim says she is worried about her health as haeneyo drink in seawater while diving.“We consider ourselves as part of the sea because we immerse ourselves in the water with our own bodies.”

Shaimaa Khalil
Reporting from Fukushima

There's been a great deal of anger and anxiety today in Fukushima. Local fishermen are worried about perception and have called it a "second disaster" for their livelihoods after the 2011 nuclear meltdown.

Tiffanie Turnbull
BBC News

Image source, EPA

As we've seen, there's been immediate concerns about the safety of seafood now. China has just banned all Japanese fish imports.

But experts say concerns about the effects of treated water on seafood has “no basis in scientific evidence”.

Mark Foreman, an Associate Professor of Nuclear Chemistry in Sweden, has previously said those who eat heaps of seafood will only be exposed to “low” doses of radiation - in the range of 0.0062 to 0.032 microSv per year.

Again, humans can safely be exposed to tens of thousands of times more than that - up to 1,000 microSv of radiation per year.

Professor Gerry Thomas, a former professor of Molecular Pathology, Imperial College London, also dismissed questions whether the wider food chain will also be at risk.

“The answer to this question [is] a resounding “no!”

Tessa Wong
Asia Digital Reporter

Japanese authorities and Tepco officials have been facing a welter of criticism, and it's prodded them to mount a comprehensive publicity blitz.

In Japan, they have put out explanatory pieces in local media, paid for posters in airports and train stations, organised public education events and school tours, and even set up livestreams of fish swimming in tanks of the treated water. They've also invited foreign delegations and news outlets - including the BBC - to tour Tepco's premises.

Online, Tepco and various Japanese government ministries have published reams of explainers in Japanese and English. Tepco even has an entire portal dedicated to the topic which comes in different versions aimed at readers in China, Hong Kong, Taiwan and South Korea - places which have levied criticism or put in place Fukushima seafood bans.

Tepco is also promising to post on its website hourly updates of the radiation levels at various stages of the water discharge process.

All this is part of Japanese Prime Minister Fumio Kishida's pledge to maintain a "high level of transparency". But it's been two years since they first announced their plan, and Japan remains deeply divided on the issue while many neighbours are rancorously opposed to the water's discharge.

Despite all their efforts, Japanese authorities have not managed to calm the waters.

As we reported earlier, China has decided to completely suspend seafood from all of Japan, expanding on an existing ban on seafood from Fukushima and some surrounding prefectures.

Now in a statement, its customs office says that it is to "protect the health of Chinese consumers".