Japan has begun releasing treated radioactive water from the wrecked Fukushima nuclear power plant into the Pacific Ocean.
The controversial, decades-long project began on Thursday, amid fresh and fierce criticism from China which slammed it as “selfish and irresponsible”.
Approved two years ago by the Japanese government and greenlighted by the UN nuclear watchdog last month, the discharge is a key step in a dauntingly long and difficult process of decommissioning the Fukushima Daiichi plant, including the removal of molten fuel.
The power plant was destroyed in March 2011 when a massive 9.0 magnitude earthquake generated powerful tsunami waves that caused the meltdowns of three of its reactors.
Plant operator Tokyo Electric Power (Tepco) said the release began at 1.03 pm local time (5.03am UK) and it had not identified any abnormalities with the seawater pump or surrounding facilities.
But China reiterated on Thursday its firm opposition to the plan and said the Japanese government had not proved the legitimacy of the water discharge.
“The Japanese side should not cause secondary harm to the local people and even the people of the world out of its own selfish interests,” China’s foreign ministry said in a statement.
China has said it would also take measures to protect the marine environment and public health, and would step up monitoring of radiation levels in its waters following the discharge.
Tokyo has in turn criticised China for spreading “scientifically unfounded claims.”
It maintains the water release is safe, noting that the International Atomic Energy Agency (IAEA) has also concluded that the impact it would have on people and the environment was “negligible”.
The release of the wastewater has unsettled other countries in the region, with Cook Islands Prime Minister Mark Brown saying that while science supported Japan’s decision, the region may not agree on the “complex” issue.
Japanese fishing groups, hit with years of reputational damage from radiation fears, have long opposed the plan. They fear it will lead to a loss of sales, including from export restrictions to major markets.
Hong Kong and Macau - both Chinese-ruled regions - are set to implement a ban on Japanese seafood from regions including the capital Tokyo and Fukushima starting on Thursday.
South Korean Prime Minister Han Duck-soo said import bans on Fukushima fisheries and food products will stay in place until public concerns were eased.
The process of pumping more than one million tonnes of treated water from the power plant is expected to take decades.
The water will be released in smaller portions initially and with extra checks. The first discharge totalling 7,800 cubic metres - the equivalent of about three Olympic swimming pools of water - will take place over around 17 days.
According to Tepco test results released on Thursday, that water contains about up to 63 becquerels of tritium per litre, below the World Health Organization drinking water limit of 10,000 becquerels per litre. A becquerel is a unit of radioactivity.
Japan will conduct monitoring around the water release area and publish results weekly, the environment minister said.
Tepco expects the process of releasing the wastewater - currently totally more than 1.3 million metric tons - to take about 30 years.
Civic groups have launched protests in Japan and South Korea, although South Korea’s government has said its own assessment found no problems with the scientific and technical aspects of the release.
Ahead of the release, a few dozen protesters gathered in front of Tepco’s headquarters in Tokyo holding signs reading “Don’t throw contaminated water into the sea!”