A South Korean delegation arrived in Japan on Sunday for a six-day visit to assess the safety of Japan's planned release of treated radioactive water into the sea from the disaster-hit Fukushima nuclear power plant.

The delegation of 21 experts in the nuclear reactor, radiation and other sectors was dispatched as concerns linger in South Korea over the potential impact of the treated water on the ocean environment.

"We will check on the safety of the process based on scientific foundation and standards," Nuclear Safety and Security Commission chief Yoo Guk Hee told reporters at Incheon airport, near Seoul.

"If we take a scientific approach to explain what we saw and what we need to confirm further, then I think people will have more trust in us," he said.

Japanese Prime Minister Fumio Kishida and South Korean President Yoon Suk Yeol agreed on Seoul's dispatch of the delegation at their summit earlier in May as the two Asian neighbors rapidly improve ties soured by disputes over history and territory.

South Korea's Nuclear Safety and Security Commission chief Yoo Guk Hee (C) speaks to reporters on May 21, 2023, at Incheon International Airport, near Seoul, before leaving for Japan. (Kyodo)

Japan plans to begin around this summer releasing the treated radioactive water that has accumulated at the Fukushima Daiichi plant on the Pacific coast, which was devastated by a powerful earthquake and tsunami in 2011.

Water has become contaminated after being pumped in to cool melted reactor fuel at the complex and has also mixed with rainwater and groundwater at the site.

Japan has pledged to discharge the water in cooperation with the International Atomic Energy Agency to ensure its safety but faces opposition to the plan from local fishermen, while neighboring countries such as Russia, South Korea and China have aired concerns.

The delegation plans to meet with officials of plant operator Tokyo Electric Power Company Holdings Inc. and other relevant Japanese institutions on Monday.

The group will inspect facilities at the plant for two days from Tuesday, including its advanced liquid processing system, or ALPS, that can remove most radioactive substances, except tritium, from the accumulated water.

On Thursday, the delegation plans to hold another meeting with the Japanese side after its on-site inspection, also including storage tanks and water supply equipment.

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