The Japanese government on Tuesday approved plans to release more than 1 million metric tons (1.1 million US tons) of radioactive water from the damaged Fukushima nuclear plant into the ocean two years from now. 

The controversial plan was approved following years of heated wrangling and despite concerns from neighboring countries. 

In response, the South Korean foreign ministry summoned Japan's top envoy to Seoul. 

South Korea's Vice Foreign Minister Choi Jong-moon met with Japanese Ambassador Koichi Aiboshi, according to officials.

Choi was expected to express regrets and lodge a protest during the meeting.

Why is Japan releasing Fukushima discharge? 

The decision was taken in a meeting of Prime Minister Yoshihide Suga's cabinet, with the backing of the International Atomic Energy Agency (IAEA).

Japan's Suga said that getting rid of the water was an "inevitable task" in the decades-long exercise of decommissioning the nuclear plant.

He added that the release will take place only "after ensuring the safety levels of the water" and alongside measures to "prevent reputational damage."

The operator Tokyo Electric Power Company (TEPCO) — which has more than 1,000 tanks at the site —  is tasked with discharging the water.

TEPCO had claimed that the space for tanks would run out by 2022, although some officials and experts disagree.

What are the possible consequences? 

Some scientists have pointed out that the long-term effects on marine life from low-dose exposure to such large amounts of material is not yet known.

Greenpeace's senior nuclear specialist Shaun Burnie told DW that the Fukushima discharges could not be safe. 

TEPCO and Japan plan to dilute the water until tritium levels are brought down to a level suitable for release. 

"But other radioactive isotopes like Strontium 90, which could be released by these discharges, concentrates in the bones of both fish and humans, increasing cancer risks," Burnie said.  

"Any radioactivity that's released into the environment will have a consequence... [it] doesn't mean there's an inevitability that is guaranteed that you will have a health effect of cancer, but it increases the radiation burden and that's not acceptable."

Burnie said an the alternative to Japan's decision could be long term waste storage, adding that the Japanese government had previously said there would be available space outside the Fukushima nuclear plant to store its waste. 

What is the response to Japan's decision? 

There has been strong local opposition to the move, and neighboring countries such as China have also expressed their concerns. 

"China has expressed grave concern to the Japanese side through the diplomatic channel, urging Japan to handle the issue of wastewater disposal from the Fukushima nuclear power plant in a prudent and responsible manner," Beijing's Foreign Ministry spokesperson Zhao Lijian said on Monday.

South Korea's Yonhap News agency quoted the country's foreign ministry official Choi Young Sam, saying that Japan's decision "can have direct and indirect impact on the safety of our people and the surrounding environment." 

The decision comes a decade after the reactor at the Fukushima Daiichi Nuclear Power Station was wrecked in a meltdown following a tsunami in 2011. 

Correction: This article has been updated to make clear that the release of tritium into the ocean is at an acceptable level 

dvv/aw (AFP, AP, dpa, Reuters)