Simulation of an attack on a nuclear power plant in South Korea (JBPress)

This is an English translation of an article originally written in Japanese. You can read the original text here.

June 26, 2025

Simulation of an attack on a nuclear power plant in South Korea

By: Miki Aoki

Part I. North Korea’s drone attack spreads radiation, 10 million people in Japan are evacuated… US intervention leads to war

Nuclear facilities have been prominent targets of attacks in international conflicts such as the Ukraine war and the Israeli-Iranian conflict. On the morning of June 22 (Japan time), it was announced that the US military had attacked Iranian nuclear facilities.

So, if an emergency were to occur on the Korean Peninsula and a nuclear power plant in South Korea were to be attacked, what would happen in East Asia, including Japan? The results of a simulation conducted by experts from Japan, the United States, and South Korea, which envisaged such a scenario, have been published. If the Kori Nuclear Power Plant in South Korea, the world’s largest operating nuclear power plant, were to be attacked, serious radioactive contamination would result in 10 million evacuees in Japan alone, the United States would request the dispatch of the Self-Defense Forces, and Japan would fall into serious chaos. Can these results really be laughed off as fantasy? We will present the shocking results of the simulation in three parts.

Shocking simulation by US NGO

The simulation was carried out by the US NGO “The Nonproliferation Policy Education Center (NPEC).” The center is a specialist institute that conducts research and education on policies related to nuclear proliferation issues, and its recommendations and statements are frequently quoted by media around the world.

About 30 people participated in this simulation, including U.S. military personnel, congressional staff, nuclear experts, and former senior officials from Japanese and South Korean government agencies involved in nuclear administration. After four years of preparation, the tabletop exercise was conducted twice last year, and the results were compiled in a report titled “Strategic Distraction: Pyongyang’s Proxies Target South Korea’s Reactors.”

Now let’s take a look at the content, including testimonies from participants.

Premise

The Moon Jae-in administration (2017-2022) in South Korea had adopted a nuclear phase-out policy, learning from the disaster at the Fukushima Daiichi Nuclear Power Plant in neighboring Japan in 2011. In response, his successor, President Yoon Seok-yeol (impeached and removed from office in April 2025 for plotting civil unrest), shifted to promoting nuclear power, saying, “I will scrape the nuclear phase-out policy and build the strongest nuclear power country.”

The Kori Nuclear Power Plant consists of eight reactors lined up along the coast of Busan and Ulsan in southeastern South Korea. The distance to Kyushu is about 200 km in a straight line. In the case of a nuclear accident, “200 km” is not a long distance at all. The worst-case scenario drawn up by experts at the time of the Fukushima Daiichi Nuclear Power Plant accident stated that a voluntary evacuation area should be set up within 250 km of the nuclear power plant. 

Phase 1: Drone attacks South Korean nuclear power plant, what will Japan, US and South Korea do?

May 31, 2026: Drone attacks the Kori Nuclear Power Plant

As pro-independence forces grow in Taiwan, Chinese President Xi Jinping decides that “military action is the only way to unify Taiwan,” and China tells North Korea that “this is the ideal time for the Korean Peninsula to be united again.” A few days later, three drones explode over the Kori Nuclear Power Plant in South Korea. No damage was done, but the fear in the region was heightened.

US activities

Regarding the drone explosion, he argued, “Looking at what’s happening in Ukraine, if one drone can reach it, thousands of drones can reach it.” In the absence of clear evidence of China’s involvement, the US government has decided that China should be publicly held responsible.

The United States will then issue a statement arguing that a diplomatic gesture would deter further North Korean attacks and dissuade China from taking action against Taiwan. The United States will send a draft statement to the governments of Japan and South Korea, requesting their support and cooperation.

South Korea’s activities

Chaos ensues within South Korea, as a cyber attack occurs on the country’s power grid, causing widespread power outages and communications disruptions.

They are trying to identify the “culprit” behind the drone attack, but are unable to reach a definitive conclusion.

“(If the Kori Nuclear Power Plant were to be attacked in earnest) the fires caused by the spent fuel would be huge, and the amount of radiation exposure would be greater than in Chernobyl or Fukushima, and local residents could develop cancer,” they argued. In the event of a full-scale attack on the nuclear power plant, they would request assistance from the United States, as their stockpile of medicines to deal with radiation exposure is weak.

Japan’s activities

The Japanese government has strong concerns about the U.S. government’s draft statement that directly criticizes China. If Japan were to support the statement, it has determined that “there is a concern that Japan-China relations will worsen further and Japan will be drawn into military action.”

Following the cyber attacks and intermittent power outages, there were strong moves toward cooperation among Japan, the United States, and South Korea, but formulating a unified response plan proved difficult.

Phase 2: Simultaneous attacks on nuclear power plants, radioactive materials spread throughout Japan

Second stage: 1-2 weeks after the drone attack, a full-scale attack on the Kori Nuclear Power Plant will begin

A mysterious group calling themselves “Korean patriots” launches a drone attack on the Kori Nuclear Power Plant. As a result, the nuclear power plant is no longer able to cool, and a large amount of radioactive material is confirmed to be released from the reactor building. The radioactive material spreads to Japan, and large-scale evacuation of residents begins in both countries.

China violates Taiwan’s airspace and sends naval vessels into the Taiwan Strait.

• USA: A joint statement was issued stating that “if China and North Korea launch further attacks, we will not hesitate to retaliate strategically, including with nuclear weapons.”
• South Korea: Expressed “immediate support for the US government .”
• Japan: Cautious, saying that “the statement should include civilian protection, humanitarian assistance, and regional stability, and military confrontation should not take precedence.” Expressed strong discomfort with the “hardline stance” of the US and South Korea.
• USA: Opinions are beginning to split within the US government. Some have suggested that the level of military response should be increased by deploying troops to Taiwan and South Korea, while others have suggested that a military response would lead to “all-out war,” and that a diplomatic approach should be emphasized.
• South Korea: The “culprit” of the drone attack has yet to be identified. For this reason, there is a conflict between those who say “we should acknowledge North Korea’s involvement and take a strong stance” and those who are cautious and say “we should not make a definitive decision without evidence.” They ask the US to “respond to the disaster” by providing medical support, radiation measurements, and evacuation transportation.
• South Korea and Japan: Residents in both countries panic and evacuate. Social order is shaken, and transportation and communications are also in disarray.
• The United States decides to launch unilateral military action against North Korea.

Phase 3: The United States intervenes militarily, and China launches an invasion of Taiwan.; U.S. military action and entry into war

• United States The US military launches missile attacks on North Korea’s submarine-launched ballistic missile bases and uranium enrichment facilities.
• North Korea The submarine fleet is devastated, and nuclear-related facilities are forced to temporarily shut down. In retaliation, North Korea deploys ground forces near the 38th parallel, places missiles along the demilitarized zone (DMZ) with South Korea, and launches cyber attacks on
• US forces and infrastructure in South Korea. The situation suddenly becomes wartime mode.
• South Korea Expresses strong dissatisfaction and distrust that the US attacked North Korea without prior consultation.
• China Implements a full naval blockade around Taiwan and begins an amphibious operation on Taiwan. The People’s Liberation Army of China occupies the islands surrounding Taiwan and begins landing on the main island. At the same time, Taiwan’s domestic communication network is seriously disrupted.
• United States Decides to send a US fleet to defend Taiwan. In cooperation with Japan and Australia, they try to break through China’s naval blockade. They request Japan to “send the Maritime Self-Defense Force in cooperation with Japan and Australia to counter China’s blockade line.”
• Japan The Japanese government has maintained its stance that the Self-Defense Forces must be approved by the Diet before they can be deployed overseas, and has taken a cautious stance toward the request from the United States. Japan is currently facing a humanitarian crisis caused by the nuclear disaster, and has little spare capacity to respond to military demands.

The Government of Japan sends the following message to the United States:

“Under the Japan-U.S. Security Treaty, Japan does not consider this incident to be a ‘direct military attack on Japan,’ and therefore has the right to reject the U.S. request. However, we will cooperate with the U.S. to the extent that we respond to humanitarian crises. Under the Japanese Constitution, the Self-Defense Forces cannot take part in offensive operations against foreign countries. In addition, this request to dispatch the Maritime Self-Defense Forces is related to Taiwan, not against North Korea.”

At this stage, the number of people wanting to evacuate within Japan would reach tens of millions, causing catastrophic chaos at airports and ports. The Japanese government lacked the know-how to handle large-scale evacuations. For this reason, the Japanese government requested neighboring countries to handle emergency visa requests and provide transportation support.

　However…

Part II. The US plans to attack China and North Korea, and Japan refuses military cooperation… What’s dangerous is spent nuclear fuel

If the Kori Nuclear Power Plant in South Korea were to be attacked by another country, serious radioactive contamination could result in 10 million evacuees in Japan alone, and the United States could request the dispatch of its Self-Defense Forces, plunging Japan into serious chaos.

The Nonproliferation Policy Education Center (NPEC), a US NGO, has come up with this answer through a detailed simulation. Approximately 30 nuclear experts from Japan, the US and South Korea participated in the simulation. We interviewed Tatsujiro Suzuki, former Deputy Chairman of the Atomic Energy Commission of the Cabinet Office and visiting professor at Nagasaki University (specializing in nuclear policy and science and technology policy), the only person from Japan who participated in the project, and asked him about the lessons learned from the simulation.

What was the “Japanese Prime Minister” thinking and how did he act?

Suzuki’s role in this simulation was “the Prime Minister of Japan.” When he was asked to do the simulation, he said, “I didn’t need to think about who the actual Prime Minister is. I was told to just act according to my own ideas.” In addition to the Prime Minister, the Japanese team included the Minister of Defense, the Minister of the Environment, the Chairman of the Nuclear Regulation Authority, the Minister of Foreign Affairs, the Minister of Economy, Trade and Industry, the Minister of Justice, and the representative of the Association of Governors (the governors of Fukuoka and Yamaguchi prefectures). All Japanese positions were filled by Americans, except for the role of the Prime Minister.

“The simulation begins with the assumption that the Kori Nuclear Power Plant in South Korea has been attacked by a drone, but first we need to consider who was responsible for the attack. If a missile had been used, it would clearly have been a military attack. However, this time it was a drone. Both South Korea and Japan are of the opinion that ‘North Korea may have been responsible, but there is no evidence.’ The United States appears to have based its intelligence activities on the belief that ‘North Korea must have been responsible.'”

“This is where the information gap arises. In fact, we were not informed of the premise of this scenario. It goes like this: Taiwan becomes more and more independent, and in response, China begins to consider a military invasion of Taiwan. China then suggests to North Korea that it should launch a military attack on South Korea’s nuclear power plant. The participants were not informed of this. Things move forward in a situation where it is unclear who is responsible for the drone attack.”

An attack on the Kori Nuclear Power Plant would spread radioactive material into the atmosphere on the eastern side of the Korean Peninsula, forcing 10 million people in Japan and several million in South Korea to evacuate. However, the United States decides to attack China and North Korea, and pressures Japan and South Korea to join in the military attack.

The US does not act according to Japan’s wishes

“Protecting citizens is the top priority. As the prime minister of Japan, I have first asked the chairman of the Nuclear Regulation Authority to calculate the number of people who will need to be evacuated. I used the diffusion assumptions created by Kang Jeong-min, former chairman of the South Korean Nuclear Safety Commission. The wind is blowing toward Japan, and I have determined that 10 million people need to be evacuated. I have asked the Minister of Foreign Affairs and the Minister of Defense to gather information. I ask the United States for assistance in evacuations and nuclear safety.”

However, the United States did not act according to Japan’s wishes. Although they agreed to send rescue teams, as they did after the Fukushima nuclear accident, they continued to hesitate in providing assistance for the evacuation of residents. Instead, they asked Japan to participate in statements calling for an “attack on China and North Korea.”

“The US demanded that Japan and South Korea sign a joint statement on military attack within a day or two. Japan consulted with South Korea, but decided to buy time by saying, ‘With regards to the Japanese government’s participation in military action, our peace constitution stipulates, Article 9 of the constitution. Furthermore, based on the security legislation, we cannot deploy troops without the approval of the Diet.’ We communicated to South Korea and the US that ‘Japan cannot take action unless the Diet approves that this is truly a crisis that concerns the survival of Japan.'”

“We demanded evidence from the US that the drone attacks were really carried out by North Korea, but they were reluctant to provide any information. We were at a loss, and in the end, the Japanese government refused to provide military cooperation unless there was evidence, and the tabletop exercise ended with that.”

How did the evacuation of Japanese citizens proceed following the attack on the Furusato Nuclear Power Plant?

“The plan was based on the assumption that the whole of western Japan would be covered in radioactive material and that 10 million people would have to evacuate. These people would have nowhere to escape to within Japan, so they had no choice but to go overseas. So we asked neighboring countries to accept the evacuees. Japan has no experience in transporting large numbers of evacuees by air or ship overseas, so we asked them to send ships and planes. We also asked Australia and Southeast Asia, but it didn’t work out. It was difficult.”

“Spent nuclear fuel pools” are dangerous

One notable feature of the latest simulation by NPEC is that the target of the attack was the “spent nuclear fuel pool” at the Furusato Nuclear Power Plant. What did Suzuki think of this?

“The biggest concern in the Fukushima Daiichi nuclear accident was damage to the spent fuel pool. People wondered if the water in the pool had run out when Unit 4 exploded. The nuclear fuel pool is on the top floor of the reactor building, and if the water is lost, a large amount of radioactive material will be released from the nuclear fuel. That’s the most frightening thing.”

“In fact, at the time of the Fukushima nuclear accident, Atomic Energy Commission Chairman Kondo Shunsuke prepared a worst-case scenario simulation under the instructions of Prime Minister Kan Naoto. I was Deputy Chairman of the Atomic Energy Commission. According to this simulation, a total of 50 million people within a 250-kilometer radius of the plant, including Tokyo, were required to evacuate. In the end, a worst-case scenario was averted as a result of a series of coincidences in which water flowed into the nuclear fuel pool of Unit 4 from another location…Currently, the nuclear fuel pools at Japan’s nuclear power plants are almost full with spent fuel.”

What lessons have been learned from the NPEC simulation? What does Suzuki think?

“In times of real emergency, every country puts its own country first. It prioritizes its own country’s interests. Top leaders have no choice but to put their own country’s people first. This was clearly evident in the latest simulation. In the end, the fact remains that cooperation between Japan and the United States has become strained. When your own family is in trouble, can you go and help your neighbor? That is the problem.”

“In Japan, there is the Rokkasho Reprocessing Plant (Aomori Prefecture), which is like a mass of spent fuel and is one of the largest in the world. What would happen if Rokkasho were attacked? I was afraid of that. At the end of last year, a report in the Financial Times revealed that Russia was targeting nuclear-related facilities in Tokaimura. In other words, there is a possibility that we could be targeted. I keenly felt that we had to think with that assumption in mind.”

“After Russia attacked the Ukrainian nuclear power plant, we need to know that anything can happen. Of course, we need to move the discussion forward in the direction of getting all countries to promise, as an international norm, that they will not attack nuclear facilities. However, national security also requires us to think about the worst case scenario. We need to give serious thought to how we can protect our people when that happens.”

Part III. If a nuclear power plant in Japan were attacked… If the Rokkasho Reprocessing Plant were attacked, the maximum number of evacuees would be 89.2 million people

Nuclear power plants are vulnerable to external armed attacks. This fact is widely known, but the results of a simulation by the US NGO “The Nonproliferation Policy Education Center (NPEC)” showed serious results, stating that “if the Kori Nuclear Power Plant in South Korea were to be attacked, serious radioactive contamination would result in 10 million evacuees in Japan alone.” The experts who made this prediction calculated that up to 40 million residents in Japan would be ordered to evacuate.

So, what would happen if a nuclear facility in Japan were to be attacked, rather than one in South Korea? 

Nuclear power plants are vulnerable to missile attacks”

Kang Jeong-min, former chairman of the South Korean Nuclear Safety Commission, who participated in the NPEC tabletop exercise, is known for repeatedly warning that nuclear power plants are vulnerable to military attacks such as missile attacks. In fact, in addition to the Kori Nuclear Power Plant used in this simulation, Kang has also independently conducted accident simulations at Japan’s Rokkasho Reprocessing Plant (Aomori Prefecture) and Kyushu Electric Power’s Genkai Nuclear Power Plant (Saga Prefecture).

Let’s take a look at the details. All simulations were calculated based on weather condition data for the first day of each month in 2019.

Furusato Nuclear Power Plant = This Simulation

At the Furusato Nuclear Power Plant, it was assumed that a nuclear accident would occur in the spent nuclear fuel pool of Unit 3, which contained 910 tons of spent nuclear fuel as of 2019. If the pool were to catch fire, the amount of cesium-137 released would be about nine times that of a nuclear fuel meltdown in the reactor.

The number of evacuees in South Korea due to evacuation orders will be an average of 8.5 million, with a maximum of 50 million. In Japan, the average number will be 5.1 million, with a maximum of 40 million. In Japan’s case, if voluntary evacuations are included, the maximum number will be 118.6 million. Japan’s total population will be 123.8 million in 2024, the year the simulation was conducted, meaning that almost all Japanese people will evacuate or attempt to evacuate.

Rokkasho Reprocessing Plant (Aomori Prefecture)

Regarding the Rokkasho Reprocessing Plant, NPEC points out that “it is one of the world’s largest spent nuclear fuel storage facilities, and if attacked, there is a possibility of a spent nuclear fuel fire equivalent to multiple Chernobyl accidents.”

As of the end of January 2019, 2,968 tons of spent nuclear fuel are stored there. If this pool were to catch fire, the amount of cesium released would be 25 times that of a core meltdown accident. The amount of released cesium would be extremely large. However, due to its geographical location, only parts of Japan and Russia would be affected by the radioactive material.

According to the figure below, Hokkaido will suffer the most damage. The number of people who will be required to evacuate in Japan will be 6.4 million on average, and 62.1 million at most. If voluntary evacuation is included, the number will be 89.2 million at most.

The Rokkasho Reprocessing Plant is owned by Japan Nuclear Fuel Limited. It is a facility that processes spent nuclear fuel from nuclear power plants around the country and extracts plutonium and uranium. It is expected to become the center of Japan’s nuclear fuel cycle, and spent fuel is collected from all over the country, making it one of the largest collection points in the world.

However, more than 30 years have passed since it was scheduled for completion in 1993, and the facility is still not finished. Due to continued technical issues, mistakes, and troubles, the facility has been postponed for the 27th time.

Genkai Unit 3 (Saga Prefecture)

Kyushu Electric Power’s Genkai Nuclear Power Plant Unit 3 has an output of 1.18 million kilowatts. According to Kang’s assumptions, if this plant were to come under attack, the spread of radioactive materials would result in an average of 1.32 million people being forced to evacuate nationwide, with a maximum of 9.49 million people. If voluntary evacuation is included, the average number of evacuees in Japan would be 2.55 million, with a maximum of 12.41 million people.