In this blog post, I will examine the Fukushima nuclear accident, the safety of South Korea’s nuclear power plants, the issue of extending the lifespans of aging reactors, and the economic costs of nuclear power to consider whether it is necessary to continue building new nuclear power plants and extending the lifespans of existing ones.

What Did the Fukushima Nuclear Accident Reveal?

On March 11, 2011, a massive magnitude 9.0 earthquake and a tsunami struck northeastern Japan. As a result, the Fukushima Daiichi Nuclear Power Plant lost its power supply and key safety functions, causing the cooling systems that keep the reactors cool to malfunction. Ultimately, a hydrogen explosion occurred at Unit 1 on March 12. Subsequently, hydrogen explosions also occurred at Units 3 and 4. During the accident, the reactor cores in Units 1 through 3 melted down, and enormous amounts of radioactive material were released into the environment. The high radiation levels measured at the time of the accident were extremely high, even when compared to radiation exposure limits for nuclear power plant workers. In Japan, the radiation exposure limit for workers is generally set at 100 mSv over a five-year period and 50 mSv in any single year.
The Fukushima nuclear accident was rated Level 7 on the International Nuclear Event Scale (INES), the highest level, which is the same rating as the 1986 Chernobyl accident. The spread of radioactive materials and the evacuation of residents following the Fukushima accident had long-term effects on Japanese society. Even now, in 2026—15 years after the accident—decommissioning work continues at the Fukushima Daiichi Nuclear Power Plant, and the removal of fuel debris from inside the reactors is expected to take a long time. Although the 20-kilometer exclusion zone established at the time of the accident is no longer maintained in its original form, there are still areas in some regions where access and residence are restricted.

Was the lifespan extension of Kori Unit 1 safe?

On the evening of April 12, 2011, Unit 1 of the Kori Nuclear Power Plant in South Korea ceased operations. The shutdown was caused by an incident in which the internal connection terminals of a circuit breaker—which supplies power to various pumps inside the reactor—were damaged due to overheating. The Gori Nuclear Power Headquarters of Korea Hydro & Nuclear Power, which was in charge of the Gori Nuclear Power Plant, explained that it was “a very minor malfunction, comparable to a circuit breaker tripping in a residential home,” but since this occurred shortly after the Fukushima nuclear accident, it raised significant concerns. Gori Unit 1 began commercial operation in April 1978 and had an initial design life of 30 years. Based solely on its original design life, it should have been shut down around 2007, but the government extended its lifespan to allow continued operation. Civil society, including environmental groups, demanded the suspension and shutdown of Gori Unit 1. However, the decision to extend its lifespan was made on the grounds that while building a new nuclear power plant would require enormous costs, existing plants could continue operating through parts replacement and maintenance. Gori Unit 1 was eventually permanently shut down on June 18, 2017, and in 2025, approval was granted for the decommissioning of South Korea’s first nuclear power plant.
However, Gori Unit 1—South Korea’s first commercial nuclear power plant—experienced numerous malfunctions and accidents since its construction. As of 2011, a total of 127 malfunctions and accidents had occurred, accounting for approximately 20% of the 643 total nuclear power plant incidents; of these, 45 occurred in the 2000s, when the plant had entered its aging phase.
This was a high figure even when compared to other power plants that began operations in the 1980s. Furthermore, it was belatedly revealed that a complete power outage occurred for 12 minutes starting at 8:34 p.m. on February 9, 2012. At the time, not only did the emergency diesel generators—which are supposed to activate automatically within 10 seconds after an external power outage—fail to start, but this critical situation was also not properly reported to higher authorities, leading to criticism that there were problems with crisis management capabilities. If the power outage had lasted for an extended period, it would have been difficult to rule out the possibility of a “meltdown”—a phenomenon in which the reactor core melts due to rising temperatures—similar to the Fukushima nuclear accident. The prolonged loss of power and cooling capabilities were also among the key causes of the Fukushima nuclear accident.

Is South Korea Safe from Earthquakes?

The Fukushima nuclear accident is not just someone else’s problem. South Korea, too, must consider the possibility that its nuclear power plants could be exposed to natural disasters such as earthquakes. Official earthquake observations in South Korea began in 1978. Since then, approximately 900 earthquakes have been officially recorded, and hundreds of earthquakes with a magnitude of 3.0 or higher—strong enough to be felt by people—have occurred. Among these, several earthquakes with a magnitude of 5.0 or higher have been recorded. Korea Hydro & Nuclear Power (KHNP) has long argued that the seismic design of South Korea’s nuclear power plants is sufficient, based on the maximum earthquake magnitude observed in the vicinity of the Kori Nuclear Power Plant over a specific period in the past. However, it is necessary to carefully examine whether seismic risks on the Korean Peninsula can be adequately assessed based solely on instrumented seismic observations from a relatively short period.
Analysis of geological activity covers a timeframe much longer than the period of official seismic observation. Therefore, geologists assess earthquake patterns not only through seismic data accumulated over several decades but also through historical records. Records from 1643 (the 21st year of King Injo’s reign) state, “An earthquake struck Gyeongsang Province, causing many signal towers and fortifications to collapse. In Ulsan, the ground split open and water gushed forth.” Records from 1681 (the 7th year of King Sukjong’s reign) note, “In Yangyang, Gangwon Province, the sea water churned violently, and a massive rock at Sinheung Temple on Mount Seorak collapsed.” These earthquakes recorded in historical texts are estimated to have had a magnitude of approximately 6.7. Geologists have long inferred from historical data that strong earthquakes likely occurred on the Korean Peninsula over an extended period before official seismic observations began. Such powerful earthquakes are not limited to historical records alone. On March 19, 1952, while the Korean War was in full swing, a strong earthquake with a magnitude of 6.3 struck the Korean Peninsula.
Gori Unit 1 was designed to withstand an earthquake of magnitude 6.5. In December 2007, during a review of nuclear safety measures to extend the operating life of Gori Unit 1, arguments were raised that the unit’s seismic design needed to be strengthened, but these were not implemented. The reason given was that not only would the reinforcement costs be substantial, but the losses incurred from shutting down the nuclear power plant for several months during construction would also be significant. However, concerns have repeatedly been raised that active faults exist in the coastal areas of Gyeongsang Province, where nuclear power plants are concentrated, and that the risk of earthquakes must therefore be given due consideration. Among these, in Haseo-ri, Yangnam-myeon, Gyeongju, North Gyeongsang Province, a fault plane with a distinct boundary between the upper and lower strata was observed, leading to the area being assessed as a large-scale active fault zone. In particular, regarding Wolseong Unit 1, it was pointed out that, given the relatively close proximity of the power plant to this fault, a thorough review of the seismic risk was necessary.
Nevertheless, ongoing review is needed to determine whether the risk of large-scale earthquakes in the East Coast regions of South and North Gyeongsang—where nuclear power plants are densely concentrated—has been adequately assessed.

Can safety be determined solely by the probability of a nuclear accident?

In 1975, the U.S. Nuclear Regulatory Commission published a report titled “A Study on Reactor Safety.” Known as the “Rasmussen Report” after its lead researcher, Norman Rasmussen, this report assessed reactor safety by comparing the probability of a reactor accident to that of other accidents, such as fires or airplane crashes. Based on 1969 population figures, the report assessed the probability of death from a reactor accident as extremely low if 100 reactors were in operation. Citing this report, the U.S. nuclear industry claimed that the likelihood of a core meltdown in a reactor was roughly equivalent to a meteorite striking a stadium—or an event that might occur once every tens of thousands of years. However, these claims by the nuclear power industry did not last long. This was because a major accident occurred on March 28, 1979, at Unit 2 of the Three Mile Island Nuclear Power Plant (TMI-2) in the United States. An accident said to occur only once every tens of thousands of years had happened in less than four years. Due to a problem with the cooling system, the reactor overheated, causing part of the core to melt and releasing radioactive material. Following the accident, nearby residents were evacuated. After the Three Mile Island accident, the construction of new nuclear power plants in the United States slowed significantly, and debates over the safety and economic viability of nuclear power continued for a long time. Subsequently, policy shifts emerged in the U.S. regarding the continued operation of existing nuclear power plants and the restart of idled reactors. Considering that it has not yet been a century since humanity began nuclear power generation, the major nuclear accidents experienced to date demonstrate that it is difficult to guarantee safety based solely on probability calculations. Can we turn a blind eye to the reality we have faced simply because the probability of an accident is very low?
When the Chernobyl accident occurred, Western governments and the nuclear industry pointed to structural problems at the Chernobyl Nuclear Power Plant itself, along with the Soviet government’s attempts to cover up the accident, as the causes of the major disaster. They argued that the damage was exacerbated because the Chernobyl Nuclear Power Plant lacked shielding facilities—such as Western-style containment vessels—capable of preventing the external release of radioactive material. However, the Fukushima nuclear accident demonstrated that even with multiple layers of defense and various safety mechanisms in place, it may be difficult to prevent a major accident when a large-scale natural disaster coincides with a prolonged loss of power. Hydrogen generated during the accident accumulated inside the reactor buildings, leading to hydrogen explosions in Units 1, 3, and 4. Furthermore, during the accident response, various measures were necessary to manage reactor pressure and prevent further releases of radioactive material.

Why is recovery after a nuclear accident so difficult?

Meanwhile, the cleanup following a major accident at a nuclear power plant is extremely difficult. In the early stages of the accident, media reports showed helicopters being used to drop water onto the reactors. These scenes revealed that, much like when fighting wildfires, the helicopters could not fly close enough to the reactors to pour water precisely but instead had to move around while scattering the water. This was partly due to the risk of radiation exposure to the helicopter pilots, but also because radioactive materials could contaminate or damage machinery and electronic equipment. It is also difficult to ensure the stable operation of electronic equipment in high-radiation environments. Consequently, direct human access to the affected reactor or the use of conventional equipment is inevitably very limited. Although remote-controlled robots and equipment capable of operating in radioactive environments have been developed and deployed since the Fukushima accident, working in high-radiation environments remains a technically challenging task.
As of 2026, decommissioning work using robots and remote-controlled equipment continues at the Fukushima Daiichi Nuclear Power Plant, and key tasks—including the removal of fuel debris—are expected to require a significant amount of time.
The issue of treating cooling water and contaminated water for recovery is also serious. As discussed earlier, the water injected to cool the reactors has become contaminated water containing high concentrations of radioactive substances and has accumulated inside the nuclear power plant. Since the accident, Japan has been simultaneously managing the contaminated water and proceeding with decommissioning work. In August 2023, it began releasing water treated by the Advanced Liquid Processing System (ALPS) into the ocean after diluting it with seawater. This release has sparked concerns and opposition from Japanese fishermen and neighboring countries, but the Japanese government and the International Atomic Energy Agency (IAEA) have maintained that the process is being managed in accordance with international safety standards. In 2026, the International Atomic Energy Agency’s review is continuing, and procedures to verify compliance with international safety standards are ongoing. As such, a nuclear power plant accident does not end as a problem confined to a single plant but gives rise to long-term issues such as contaminated water, decommissioning, resident evacuations, and environmental restoration.
Additionally, problems such as the spread of radioactive materials due to atmospheric convection or rain containing radioactive substances may also occur. This means that a nuclear power plant accident has the potential to extend beyond the borders of a single country and affect neighboring nations and regions. In other words, radioactive contamination and damage caused by a nuclear accident can spread across national borders. Therefore, the safety of nuclear power plants is not an issue that a single country can judge solely based on its own standards; it is also an issue that neighboring countries and the international community as a whole must consider together.

Is Nuclear Power Really Economical?

South Korea is ranked among the top five nuclear power nations in the world, and the Lee Myung-bak administration touted the export of nuclear power plants overseas based on the scale and technological capabilities of the domestic nuclear power industry. Above all, it emphasized that nuclear power plants are safe. However, as a series of incidents has shown, there are limits to predicting and preparing for accidents like the one in Fukushima—where a massive earthquake and tsunami occurred simultaneously—through simple probability calculations. The accident did indeed occur, causing immense damage, and recovery efforts are still ongoing in 2026, 15 years after the accident. It is difficult to conclusively assert that a nuclear power plant’s safety measures and systems will completely prevent an accident. This is because it is hard to guarantee with absolute certainty that safety measures will function properly even in the event of a major accident, or that multiple safety measures will not fail simultaneously.
A nuclear power plant explosion must never occur under any circumstances. Everyone would agree on this point. Nevertheless, proponents of nuclear power argue that the safety of nuclear power plants is a matter that can be addressed through technological improvements, while emphasizing that no other form of power generation is as economical as nuclear power. This is the most important basis for their argument. But is nuclear power really economical?
Proponents of nuclear power calculate only the cost per unit of electricity generated and claim that nuclear power is a much cheaper energy source compared to other forms of power generation. In fact, as of 2011, the unit cost of nuclear power was 39.1 won/kWh, which was lower than that of oil (223.7 won/kWh), LNG (142.3 won/kWh), and anthracite coal (67.1 won/kWh). However, this calculation does not sufficiently account for opportunity costs resulting from accidents, environmental restoration costs, construction costs, decommissioning costs, and nuclear waste disposal costs. Furthermore, it is important to consider that a significant portion of these additional costs may persist long after the plant’s operational lifespan has ended. Therefore, rather than judging the economic viability of nuclear power based solely on the unit cost of electricity, it is necessary to examine the costs across its entire life cycle—from construction and operation to accident risks, decommissioning, and waste management.
Let’s examine construction and decommissioning costs. While these vary depending on generating capacity, the construction cost of a nuclear power plant at that time was around 2 trillion won—significantly higher than the 200 to 500 billion won for a thermal power plant or the 1 trillion won for a hydroelectric plant—and it also involved additional technology development costs. Furthermore, the cost of decommissioning a nuclear power plant—an aspect that is often overlooked—is an even bigger issue. This is because many people tend to think of decommissioning as a problem that arises only after the plant has ceased operations. However, a nuclear power plant cannot simply be dismantled immediately upon ceasing operations, unlike conventional power plants. Since facilities and equipment contaminated with radioactive materials must be dismantled and radioactive waste managed, the process requires a long period of time and significant costs. In the case of Kori Unit 1, procedures related to the decommissioning plan were initiated following its permanent shutdown, and in 2025, South Korea’s first nuclear power plant decommissioning approval was granted. Decommissioning is estimated to require a considerable amount of time and money.
Consequently, the government has opted to extend the operational life of nuclear power plants rather than shut them down whenever possible. However, the costs associated with this are also substantial. According to data from the Korea Hydro & Nuclear Power Company (KHNP), replacing parts in nuclear power plants that were shut down due to component failures at the time incurred significant costs, and additional costs were incurred due to the shutdowns caused by these failures. Furthermore, in the case of Gori Unit 1—which has been a point of contention—substantial funds have been invested in equipment replacement and maintenance since 2007 to extend its operational life. As the level of aging increases, the costs associated with equipment replacement and ensuring safety are also likely to rise. Ultimately, the decision to extend the operating life should not be based solely on the fact that it costs less in the short term than building a new nuclear power plant; rather, it must take into account maintenance and repair costs due to aging, the costs of ensuring safety, and even decommissioning costs.

Shouldn’t we also calculate the opportunity cost of a nuclear accident?

Let’s consider the opportunity cost resulting from a nuclear power plant accident. Opportunity cost is a fundamental factor that must be considered in rational economic decision-making. The damages caused by the Fukushima nuclear accident in Japan reached a colossal scale based on estimates at the time. In South Korea as well, analyses have suggested that damages could reach hundreds of trillions of won in the event of an accident at Kori Unit 1. However, the accident contingency funds actually allocated by the government at the time were very small relative to that scale, and it was pointed out that preparations for recovery costs and compensation in the event of a plant accident were insufficient. Is this not a cost? This amounts to nothing less than failing to fully reflect the likelihood of an accident and the resulting costs—not because nuclear power is economically viable, but to make it appear so. If, as the nuclear power industry argues, “preparing for an accident that might occur once every hundreds of thousands of years would make nuclear power plants unprofitable,” does this not actually prove that nuclear power may not be economically viable?
What choice do we face now? Should we simply hope that no more nuclear power plant accidents occur? Or should we strengthen safety measures, even if it requires astronomical investments? However, if we do so, paradoxically, massive amounts of taxpayer money will be poured into the system, and the cost of electricity production will rise, which will be reflected in the electricity bills we pay. Even if we were to accept that, can we truly believe that we can control all accident factors 100 percent? As emphasized, if nuclear power goes wrong, it can cause damage that is difficult to recover from over the long term. We have seen this reality all too clearly through the Fukushima accident. Nuclear power can never be the sole solution to our energy problems. The unconditional extension of nuclear power plant lifespans must be halted, and decisions regarding the construction of new plants must be made cautiously after comprehensively considering safety, economic feasibility, and long-term social costs.