About 50,000 protesters gathered in the capital of South Korea on Saturday to demand that the government take steps to prevent what they fear is an impending disaster: Japan's release of contaminated radioactive water from the Fukushima nuclear power plant.

Japan began dumping the water from the plant north of Tokyo into the sea on Thursday, despite objections from fishing communities and others worried about the environmental impact, both at home and abroad.

"We will not be immediately seeing disasters like detecting radioactive materials in seafood but it seems inevitable that this discharge would pose a risk on the local fishing industry and the government needs to come up with solutions," said Choi Kyoungsook of the Korea Radiation Watch group that organized the rally.

Japan and scientific organizations assert that the water, distilled after being contaminated by contact with fuel rods when the reactor was destroyed in a 2011 earthquake and tsunami, is safe.

South Korea has stated that it sees no scientific problems with the water release, but environmental activists argue that not all possible impacts have been studied.

"Nobody can tell what's going to happen to the marine ecosystem in the next 100 years," said Choi.

Japan explains that it needs to start releasing the water as storage tanks holding about 1.3 million metric tonnes of it – equivalent to 500 Olympic-sized swimming pools – have reached full capacity.

The initial discharge of 7,800 cubic meters – approximately three Olympic pools in size – will occur over a span of about 17 days.

(With input from Reuters)

(Cover: People protest Japan's release of Fukushima nuclear-contaminated water into the sea in Seoul, South Korea, August 25, 2023. /CFP)