No detectable amount of tritium was found in seawater samples taken from off the site of the wrecked Fukushima nuclear power plant, where Japan began disposing of treated radioactive water into the nearby sea, the plant's operator said Friday.

Tokyo Electric Power Company Holdings Inc. released the results after analyzing the samples, taken from 10 locations within a distance of 3 kilometers of the Fukushima Daiichi power plant a few hours after the water discharge began on Thursday.

The water is being discharged into the ocean 1 km off from the plant via an undersea tunnel after undergoing a treatment process in which most radionuclides except tritium have been removed. The remaining tritium is then diluted to one-40th of the concentration permitted under Japanese safety standards.

TEPCO plans to continue taking daily seawater samples for analysis and will publicly disclose the results each following day for about a month.

Aerial photo taken from a Kyodo News helicopter on Aug. 24, 2023, shows the Fukushima Daiichi nuclear power station in northeastern Japan. (Kyodo)

The Environment Ministry also sent out four vessels Friday morning to start collecting seawater samples from 11 locations within a radius of around 50 km of the Fukushima power plant, with the results expected on Sunday or later.

The ministry plans to disclose the data it collects from its sample analyses every week for around three months.

A research institute commissioned by the Fisheries Agency conducted inspections in a sample area around the discharge outlet on Friday to monitor concentration levels of radioactive materials in fish.

The results of the tests, the first to be conducted after the water release, will be posted on the agency's website on Saturday afternoon.

The government argues discharging the treated water, which has been stored in tanks after being used to cool melted reactor fuel, is an integral part of decommissioning the nuclear plant, which was devastated by a catastrophic earthquake and tsunami in 2011.

However, concerns have persisted about its impact both within Japan and abroad, with the news of the release provoking an immediate response from some neighboring countries and local fishermen opposed to the water release.

Norio Usui, a 63-year-old fisherman from Iwaki, Fukushima Prefecture, said it was to be expected that the level of tritium would be undetectable, adding that it would be more unusual if the reverse were true.

"To minimize reputational damage, it is most important to make consumers aware of such scientific data," Usui said.

But Vern Lim, a Filipino visiting Tokyo's Ginza district with her family, expressed concerns about the impact of the water release on the health of younger generations. She commended Japan for ensuring tritium levels were below detectable limits but admitted she still feels hesitant about eating Japanese products.


China suspended all seafood imports from Japan on Thursday following the discharge's start, prompting Japan to request that it immediately lift the imposed restrictions.

Beijing on Friday also banned food production operators from purchasing or using seafood originating in Japan to process it for sale.

TEPCO President Tomoaki Kobayakawa said in a meeting with Economy, Trade and Industry Minister Yasutoshi Nishimura the same day that his company is ready to provide appropriate support to businesses affected by China's response.

The Japanese government is also considering a rescue plan for domestic fisheries to mitigate the negative impact of the ban on the industry, officials said Friday.

Authorities and TEPCO have been monitoring more than 100 spots for tritium off Fukushima, Miyagi and Ibaraki prefectures.

The International Atomic Energy Agency is also providing live data on the release of treated water from the power station on its website after having assessed that the discharge plan is aligned with global safety standards and would have a "negligible" impact on people and the environment.

IAEA chief Rafael Grossi and Japanese Foreign Minister Yoshimasa Hayashi affirmed in their video conference Friday that Japan and the IAEA will issue a document on their cooperation at an early date in a show of the U.N. agency's commitment to its role in overseeing the discharge process.

Tritium is known to be less harmful to human health than other radioactive materials such as cesium and strontium as it emits very weak radiation and does not accumulate in the body, experts say.

Nuclear power plants worldwide routinely release treated water containing low concentrations of tritium and other radionuclides into the environment as part of normal operations, according to the IAEA.

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