Photo/IllutrationThe projected spread of radioactive cesium-137 from a disaster at the No. 3 reactor’s spent fuel pool of the Kori nuclear plant in Busan, South Korea (Provided by Kang Jung-min)

  • Photo/Illustraion
  • Photo/Illustraion

A serious nuclear accident in South Korea could force the evacuation of more than 28 million people in Japan, compared with around 24 million in the home country of the disaster.

Japan would also be hit harder by radioactive fallout than South Korea in such a disaster, particularly if it occurred in winter, when strong westerly winds would blow radioactive substances across the Sea of Japan, according to a simulation by the Natural Resources Defense Council, a Washington-based think tank.

The simulation, based on a scenario of an unfolding crisis at the Kori nuclear power plant in Busan, South Korea, was led by Kang Jung-min, a South Korean senior researcher of nuclear physics, and his colleagues.

At events in Japan and South Korea, Kang, 51, has repeatedly warned about East Asia’s vulnerability to a severe nuclear accident, saying the region shares the “same destiny” regardless of the location of such a disaster.

The Kori nuclear complex is home to seven of the country’s 25 commercial reactors, making it one of the largest in South Korea. Its oldest reactor--and the first in the country--went online in 1978.

Spent nuclear fuel at the Kori plant is cooled in on-site storage pools next to reactors.

But the operator of the plant has ended up storing spent fuel in more cramped conditions than in the past because waste keeps accumulating from the many years of operations.

An estimated 818 tons of spent fuel was being stored at the pool of the Kori No. 3 reactor as of the end of 2015, the most at any reactor in the country.

That is because the No. 3 pool has also been holding spent fuel from the No. 1 and No. 2 reactors since their fuel pools became too crowded.

Storing spent fuel in such a manner greatly increases the risk of a nuclear accident, Kang warned.

Kang’s team simulated the series of likely events that would follow if the No. 3 reactor lost power in a natural disaster or an act of terrorism.

With no power, the spent fuel at the No. 3 reactor could not be cooled. The cooling water would evaporate, exposing the fuel rods to air, generating intensive heat and causing a fire.

Hydrogen gas would then fill up the fuel storage building, leading to an explosion that would result in the release of a large amount of vaporized cesium-137 from the spent fuel.

Assuming that the catastrophe occurred on Jan. 1, 2015, the researchers determined how highly radioactive cesium-137 would spread and fall to the ground based on the actual weather conditions over the following week, as well as the direction and velocity of winds.

To gauge the size of the area and population that would be forced to evacuate in such a disaster, the team took into account recommendations by the International Commission on Radiological Protection, a private entity, and other organizations.

The results showed that up to 67,000 square kilometers of land in Japan--or much of the western part of the country--would fall under the evacuation zone, displacing a maximum of 28.3 million people.

In South Korea, up to 54,000 square kilometers would need to be vacated, affecting up to 24.3 million people.

The simulation also found that 18.4 million Japanese and 19 million Koreans would remain displaced for even after 30 years, the half-life of cesium-137, in a worst-case scenario.

Radioactive materials from South Korea would also pollute North Korea and China, according to the study.

Nineteen reactors in South Korea are located in the coastal area facing the Sea of Japan, including those at the Kori nuclear power plant.

Kang said the public should be alerted to the dangers of highly toxic spent fuel, an inevitable byproduct of nuclear power generation.

One ton of spent fuel contains 100,000 curies of cesium-137, meaning that 20 tons of spent fuel would be enough to match the estimated 2 million curies of cesium-137 released in the 1986 Chernobyl disaster.

An average-size light-water reactor produces about 20 tons of spent fuel in one year of operation.

East Asia is home to one of the world’s largest congestions of nuclear facilities, Kang said.

Japan, China and South Korea, which have all promoted nuclear energy as state policy for decades, together host about 100 commercial reactors.

A number of nuclear-related facilities are also concentrated in North Korea, particularly in Yongbyon, north of Pyongyang.

If a severe accident were to occur in China, the pollution would inevitably spill over to South Korea and then to Japan.

“That is why people should take serious interest in not just their own country’s nuclear issues, but also in neighboring countries,” Kang said. “Japan, China and South Korea should cooperate with each other to ensure the safety and security of spent fuel and nuclear facilities.”

He said the risks of a fire would be reduced if spent fuel were placed at greater intervals in storage pools.

“Ideally, spent fuel should be moved to sealed dry casks and cooled with air after it is cooled in a pool for about five years,” he said.