A civic group holds a press conference to call on South Korea and the US to object to Japan's plan to release wastewater contaminated with radioactive materials from the 2011 Fukushima nuclear reactor meltdowns into the sea, in front of the Sejong Center for the Performing Arts in Seoul on April 25. (Yonhap)

Seven out of 10 South Koreans residing in the greater Seoul area expressed their opposition to Japan's move to discharge radioactive wastewater from the now-defunct Fukushima nuclear power plant into the ocean, local broadcaster CBS reported on Thursday, citing a survey.

In the poll of 1,000 people aged 18 or above conducted by polling organization Jowon C&I May 27-29, 70.8 percent of respondents said they are against Tokyo's plan to release the destroyed nuclear plant's wastewater. While 19.5 percent were in favor of the discharge of the wastewater, 9.6 percent said they were unsure.

Women aged 18-29 showed the strongest negative sentiments towards the release of the wastewater, with 88.6 percent of them objecting it.

Some 77.7 percent of women in their 40s and 77.2 percent of women in their 50s also said they disapprove of the plan.

The wrecked Fukushima plant -- three of the reactors of which melted down after being hit by a tsunami triggered by a magnitude-9.0 earthquake in March 2011 -- currently stores more than 1.3 million tons of radioactive wastewater in over 1,000 giant tanks. The radioactive wastewater was treated through a custom filtering system known as the Advanced Liquid Processing System, but still contains cesium, tritium and other radionuclides that exceed releasable limits.

In April 2021, the Japanese government announced plans to release the contaminated wastewater gradually into the sea beginning in 2023 after a dilution process, which it says could reduce the radioactivity to allowable levels. The wastewater discharge is set to begin this summer and will take at least three decades to complete, according to the Japanese government.

Late last month, the Korean government sent a team comprised of 21 experts from the Korea Institute of Nuclear Safety and the Korea Institute of Ocean Science and Technology to Japan for the on-site inspection of the Fukushima plant's facilities.

Nevertheless, 63 percent of the survey's respondents said the team's inspection of the plant's facilities has not changed their stance opposing Japan's release of the wastewater.