TOKYO -- Japan on Friday started the fifth round of release of nuclear-contaminated wastewater from the crippled Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean.

Despite opposition among local fishermen, residents as well as backlash from the international community, Tokyo Electric Power Company (TEPCO), the plant's operator, started discharging the radioactive wastewater in the morning, the first round in fiscal 2024.

Similar to the previous four rounds, about 7,800 tons of the wastewater, which still contains tritium, a radioactive substance, will be discharged until May 7.

TEPCO analyzed the water stored in the tank scheduled for release, and found that the concentrations of all radioactive substances other than tritium were below the national release standards, while the concentration of tritium that cannot be removed will be diluted with seawater, Japanese newspaper Asahi Shimbun reported.

TEPCO will measure the concentration of radioactive substances such as tritium in the surrounding waters every day during the period to investigate the effects of the release, it added.

The fishery industry and local residents have long opposed the discharge plan. About 150 fishermen and residents from Fukushima and Miyagi prefectures filed a lawsuit against the Japanese government and TEPCO at the Fukushima District Court on Sept. 8, 2023, demanding them stop releasing nuclear-contaminated water into the ocean.

On March 4, the lawsuit held its first public hearing at the Fukushima District Court, and the number of people signed on as plaintiffs has grown from about 150 to over 360.

Hideki Taki, chairman of the Retired Workers Union of the National Trade Union Council, said in a recent email interview with Xinhua that the Japanese government and TEPCO have written agreements with local fishermen in Fukushima, pledging they would not dispose of the radioactive wastewater without gaining the understanding of relevant stakeholders. However, since last August, they have disregarded the agreements and arbitrarily proceeded with the ocean discharge of nuclear-contaminated water, which is unforgivable.

The so-called "treated water" by the government and TEPCO still contains radioactive materials after being treated by advanced liquid processing system (ALPS), a multi-nuclide removal system, which TEPCO also admits.

After radioactive substances are discharged into the sea, they will inevitably enter human bodies through the food chain, but the government and TEPCO have not provided any evidence-based safety instructions on the food chain, Hideki Taki said.

Meanwhile, the decommissioning of the Fukushima plant has made little progress, and it is completely unpredictable when the nuclear waste and contaminated materials can be removed, Hideki Taki noted, adding that the government and TEPCO should immediately stop the ocean discharge.

The Fukushima nuclear-contaminated water release began in August 2023, and a total of about 31,200 tons of the water was released in four rounds in fiscal 2023, which ended in March.

In fiscal 2024, TEPCO plans to discharge a total of 54,600 tons of contaminated water in seven rounds, which contains approximately 14 trillion becquerels of tritium.