Investigating Natural Disaster-Related External Events at Nuclear Power Plants: Towards Climate Change Resilience
Abstract
Climate change is causing rapid shifts in the intensity and frequency of natural disasters worldwide, which may have implications for the safety of nuclear power plants. As these natural disasters become more frequent and severe, their potential impact on nuclear facilities is expected to increase. Several instances of nuclear power plants being forced to shut down due to climate change have already been observed. The changing patterns of natural disasters can lead to alterations in external events affecting nuclear power plants. Therefore, it is crucial to investigate how climate change could affect the safety and operations of nuclear power plants in order to establish protective measures and mitigation strategies. This study examined external events associated with climate change that could potentially impact nuclear power plants, and both Korean and international cases were summarized. Recommendations for future tasks were proposed based on these findings. Currently, there have been no significant reported cases where climate change has severely impacted the operations and safety of nuclear power plants. However, it is essential to undertake periodic evaluations, long-term management, and further research to ensure the safety and continued operation of nuclear power plants in the face of climate change.
1. Introduction
The mounting effects of human activities and industrial development on the global climate have become increasingly apparent since the late 19th century [1–4]. Recently, the effects of climate change and extreme weather conditions have worsened due to increased carbon emissions, leading to an increase in damages caused by climate change worldwide [5–8]. For instance, in 2018, the California region of the United States experienced a devastating Camp Fire, claiming the lives of 85 people [9]. This incident caused significant damage due to dry climate conditions caused by La Niña, a climate pattern characterized by abnormally low sea surface temperatures in the equatorial Pacific [10]. Similarly, in 2020, southern China witnessed unprecedented rainfall and subsequent flooding, displacing over 55 million individuals due to floods [11].
To mitigate the adverse effects of climate change, the Intergovernmental Panel on Climate Change (IPCC) regularly publishes reports every 5 to 6 years, while other institutions actively conduct extensive research on the subject. As highlighted in the IPCC’s Fifth Assessment Report, several factors, such as increased use of fossil fuels like coal and oil, deforestation, and intensified agricultural activities, are expected to significantly contribute to the accelerated escalation of climate change due to rising emissions of greenhouse gases [12]. Climate change entails a projected increase in the frequency and intensity of natural disasters such as severe storms, floods, heavy rainfall, droughts, and wildfires. These changes will likely have consequential effects on various industries [13–18]. Consequently, it becomes evident that climate change will substantially affect the safety and operation of nuclear power plants (NPPs).
Nuclear power plants are designed to mitigate the effects of natural disasters [19–23]. However, with the growing impact of climate change, the occurrence of natural disasters might surpass the plants’ design criteria or previously unanticipated scenarios [24–28]. A recent illustration of climate change’s impact on nuclear power plants was observed in Texas in 2021, a warm region in the United States all year round, where water pumps at nuclear power plants froze due to an unusual cold wave, resulting in a shutdown [29]. Similarly, heat waves and abnormally high temperatures in France resulted in shutdowns and reduced output at nuclear power plants [30]. Furthermore, in South Korea, there have been instances of the Hanul nuclear power plants undergoing multiple shutdowns due to issues related to marine organisms [31].
Climate change has already begun to affect nuclear power plants worldwide, underscoring the urgent need for protective designs and mitigation measures to ensure their continued safe operation. This study extensively reviewed existing literature to investigate the potential consequences of climate change on nuclear power plants and examined past incidents of climate-related external events. By analyzing climate-induced events and incidents in Korea using the OPIS system, the study identified key external events (typhoons/strong winds (missile), heavy rainfall, sea level rise, seawater temperature rise, marine organisms, wildfires, etc.) linked to climate change that can potentially affect nuclear power plants. Based on this analysis, a selection of climate change-related external events with the potential to affect nuclear power plants was made, and foreign cases were systematically organized. These findings offer valuable insights into the complex interplay between climate change and the operations of nuclear power plants.
2. Forecast of Climate Change
The IPCC Sixth Assessment Report assessed future climate projections using five greenhouse gas emission scenarios known as Shared Socioeconomic Pathways (SSPs) [32]. These scenarios include the following: (1) SSP5-8.5, representing a very high greenhouse gas emission scenario; (2) SSP3-7.0, representing a high greenhouse gas emission scenario; (3) SSP2-4.5, representing a moderate greenhouse gas emission scenario; (4) SSP1-2.6, representing a low greenhouse gas emission scenario; and (5) SSP1-1.9, representing a very low greenhouse gas emission scenario. Table 1 presents the projections for the average global surface temperature relative to the 1850s for each scenario [32].
| Scenarios | Period | |||||
|---|---|---|---|---|---|---|
| 2021-2040 | 2041-2060 | 2081-2100 | ||||
| Best estimate (°C) | Most likely range (°C) | Best estimate (°C) | Most likely range (°C) | Best estimate (°C) | Most likely range (°C) | |
| SSP1-1.9 | 1.5 | 1.2~1.7 | 1.6 | 1.2~2.0 | 1.4 | 1.0~1.8 |
| SSP1-2.6 | 1.5 | 1.2~1.8 | 1.7 | 1.3~2.2 | 1.8 | 1.3~2.4 |
| SSP2-4.5 | 1.5 | 1.2~1.8 | 2.0 | 1.6~2.5 | 2.7 | 2.1~3.5 |
| SSP3-7.0 | 1.5 | 1.2~1.8 | 2.1 | 1.7~2.6 | 3.6 | 2.8~4.6 |
| SSP5-8.5 | 1.6 | 1.3~1.9 | 2.4 | 1.9~3.0 | 4.4 | 3.3~5.7 |
According to the predictions of the IPCC, climate change is expected to result in more frequent and severe extreme heat events, leading to increased drought occurrences and larger areas affected by wildfires [33, 34]. The projections suggest that for every 1°C rise in temperature, there will be an approximately 7% increase in daily extreme precipitation, leading to more intense global flooding events [33, 34]. The marine environment is also likely to be affected, with a steady rise in the average global sea level throughout the 21st century due to global warming, which may contribute to the proliferation of marine organisms like jellyfish [33, 35]. In the foreseeable future, medium- to long-term climate changes are expected to result in heightened occurrences or intensities of heavy rainfall/snowfall, floods, tropical cyclones, droughts, and rising sea levels, all of which could have profound implications for industrial facilities, including nuclear power plants [36]. Figure 1 displays the geographical distribution of operational nuclear power plants worldwide as of 2023, while Figure 2 illustrates the evolving impacts of future climate change in regions hosting numerous nuclear power plant sites.
3. Impacts and Incidents of Climate Change on Nuclear Power Plants
3.1. Climate Change-Induced External Events Affecting Nuclear Power Plants
External events refer to incidents originating outside the nuclear facility that may trigger initiating events, leading to significant consequences such as severe damage or large-scale release of radioactive materials, often attributed to failures in safety systems or operator errors [31]. The impacts of such external events on nuclear power plants encompass a range of factors, including loss of off-site power and station black out, loss of the ultimate heat sink, occurrences of explosions, leaks of hazardous material, impaired ventilation functionality, and equipment degradation [39]. A comprehensive compilation of the critical external events defined in Table 2 and their relationship to climate change-induced phenomena is presented in Table 3 [40, 41].
| Major external events | Impacts on nuclear power plants [40] | Impacts on nuclear power plants [41] |
|---|---|---|
| Structure/pressure | (i) Pressure can compromise the safety functions of structures, resulting in their deactivation. |
|
| Structure/missile | (i) Potential missile strikes can compromise the safety functions of structures, resulting in their deactivation. |
|
| Cooling/ventilation | (i) The potential effect on ventilation may result in impairment or complete failure of the air cooling safety system. Furthermore, the infiltration of hazardous gases through the ventilation system poses risks to the power plant’s operation. |
|
| Cooling/heat sink | (i) The influence on the final heat sink may result in a partial or complete loss of secondary cooling and other safety systems reliant on water cooling. |
|
| LOOP (loss of off-site power) | (i) It can affect the power plant’s external power connection, resulting in the loss of off-site power. | — |
| External flooding | (i) The failure of safety systems or structural erosion affects power plants. |
|
| External fire | (i) The failure of safety systems affects power plants. |
|
| Electric | (i) The generation of electric or magnetic fields indirectly affects the power plant by potentially influencing the power supply to safety systems or control signals. |
|
| Other direct impacts | (i) The event may work in a way not covered by the general categories. An example is plant isolation. |
|
| External event climate phenomenon | Pressure | Missile | Vent. | Heat sink | LOOP | Flooding | Fire | Electric | Other |
|---|---|---|---|---|---|---|---|---|---|
| Strong winds | ○ | ○ | ○ | ○ | |||||
| Tornado | ○ | ○ | ○ | ||||||
| High air temperature | ○ | ||||||||
| Low air temperature | Freezing risk for exposed functions | ||||||||
| Extreme air pressure | ○ | ||||||||
| Extreme rain | ○ | ○ | |||||||
| Extreme snow (including snow storm) | ○ | ○ | ○ | Plant isolation | |||||
| Extreme hail | ○ | ||||||||
| Mist | Salt fog | ||||||||
| White frost | ○ | ||||||||
| Drought | (○) | An officer at seawater intake | |||||||
| Salt storm | ○ | ||||||||
| Sand storm | ○ | ||||||||
| Lightning | ○ | ○ | ○ | ||||||
| Soil frost | Freezing risk for exposed functions | ||||||||
| Avalanche | ○ | ||||||||
| Landslide | ○ | ||||||||
| External fire | ○ | ||||||||
| Missiles from other plant on site | ○ | ||||||||
| Strong water current (underwater erosion) | ○ | ||||||||
| Low seawater level | ○ | ||||||||
| High seawater level | ○ | ○ | |||||||
| High seawater temperature | ○ | ||||||||
| Low seawater temperature | ○ | ||||||||
| Underwater landslide | ○ | ||||||||
| Surface ice | ○ | ||||||||
| Frazil ice | ○ | ||||||||
| Ice barriers | ○ | ||||||||
| Organic material in water | ○ | ||||||||
| Corrosion (from saltwater) | Corrosion of the exposed area |
3.2. Investigation of Climate Change-Related Events and Cases at Nuclear Power Plants
The study utilized the Nuclear Power Plant Safety Operation Information System (OPIS), operated by the Korea Atomic Energy Safety Institute (KAERI), to identify climate-related meteorological phenomena that may affect nuclear power plants [31]. By examining OPIS records spanning from May 1978 to June 2023, a total of 771 events were documented at nuclear power plants in Korea. Events are evaluated using the International Nuclear Accident Scale (INES) defined by the International Atomic Energy Agency (IAEA). Events are classified into grades 1 to 7, with grades 1 to 3 as incidents and grades 4 and above as accidents. Also, events of no safety significance are classified as grade 0. In Korea, 71 external events without safety significance occurred at nuclear power plants. The study categorized external events into seven groups, namely, typhoons/strong winds, marine organisms, earthquakes, lightning, heavy rainfall, wildfires, and others. Figure 3 presents a quantitative analysis of the frequency of incidents caused by external events, categorized by year. The occurrence of external events at nuclear power plants has exhibited fluctuations, with a peak of 7 incidents per year and an average of 1.59 incidents since 1978.
The causes of external events were categorized into seven groups, typhoons/strong winds, marine organisms, earthquakes, lightning, rainfall, wildfires, and others, with reference to Tables 2 and 3. The frequency of occurrences for each nuclear power plant site is summarized in Table 4.
| NPP sites | External events | |||||||
|---|---|---|---|---|---|---|---|---|
| Typhoons/strong winds | Marine organisms | Earthquakes | Lightning | Rainfall | Wildfires | Others | Sum | |
| Kori/Shin Kori sites | 16 | 2 | 1 | 3 | 3 | — | 2 | 27 |
| Wolsong/Shin Wolsong sites | 2 | — | 9 | — | 1 | — | 1 | 13 |
| Hanul sites | 3 | 18 | 1 | — | 3 | — | 25 | |
| Hanbit sites | — | — | — | 4 | — | 2 | 6 | |
| Sum | 21 | 20 | 11 | 7 | 4 | 3 | 5 | 71 |
Regarding of the frequency and proportion of natural disasters leading to external events at nuclear power plants, the order can be observed as follows: typhoon/strong wind, marine organisms, earthquake, lightning, heavy rainfall, and wildfire. Specifically, the Kori/Shin Kori site experienced the highest occurrence of external events caused by typhoons, while the Hanul site witnessed a significant number of external events attributed to marine organisms. The Wolsong site encountered a total of 9 incidents related to earthquakes, with 5 of them originating from the Gyeongju earthquake on September 12, 2016. And each event occurred due to earthquakes in 2007 (Odaesan), 2014 (Gyeongju), 2015 (Gyeongju), and 2017 (Pohang). The Hanbit site encountered 4 incidents caused by lightning, with 3 of them resulting in reactor shutdowns due to lightning strikes on the transmission system.
- (i)
Typhoons/strong winds (missile)
- (ii)
Heavy rainfall
- (iii)
Sea level rise
- (iv)
Seawater temperature rise
- (v)
Marine organisms
- (vi)
Wildfires
3.2.1. Typhoons/Strong Winds
Among various external events, typhoons and strong winds have been the most recurrent causes of accidents in Korea’s nuclear power plants. It is expected that the frequency and intensity of typhoon occurrences will be influenced by climate change, as indicated by the Climate Change Assessment Report for Korea, which projects a rise in severe typhoons [42, 43]. Consequently, to strengthen preparedness and ensure the safety of nuclear power plants in the event of a typhoon, a comprehensive compilation of typhoon-induced damages has been presented in Tables 5 and 6 [31].
| Year | Detailed information on the incidents | Unit |
|---|---|---|
| 1986 | The reactor underwent a shutdown, and loss of off-site power was lost due to transformer and line damage caused by saltwater intrusion and lightning strikes. | Kori 4 |
| 1986 | Salt accumulation on the switchyard insulator surface caused continuous flashovers. Additionally, flashovers on the insulators of the transmission lines triggered the operation of overcurrent ground relays, resulting in the turbine generator and reactor shutdown. | Kori 1 |
| 1987 | An instantaneous voltage drop in the transmission line due to a phase-to-phase short-circuit accident momentarily weakened the power supply to the turbine governor, leading to the loss of functionality in the governor and the subsequent shutdown of the turbine generator and reactor. | Kori 1 |
| 1987 | A significant increase in the influx of seaweed and sediment into the intake structure caused a loss of functionality in the circulation water system, subsequently leading to the manual shutdown of the turbine generator and reactor. | Kori 2 |
| 1987 | Salt accumulation in the transformer and switchyard insulation materials triggered the operation of the differential protection relays for the main generator and main transformer, resulting in turbine and reactor shutdowns. | Kori 3 |
| 1987 | The accumulation of salt in the insulation materials of the transformers and switchyards resulted in insulation degradation, triggering the operation of the differential protection relays for the main generator and main transformer and leading to the shutdown of the turbine and reactor. | Kori 4 |
| 1987 | The simultaneous operation and tripping of protective devices in the transmission lines resulted in reactor shutdown due to the initiation of reactor power reduction and the low flow signal of the emergency cooling system. It was presumed to be caused by a momentary short circuit due to lightning or heavy rainfall. | Wolsong 1 |
| 1991 | Loss of flow in the secondary cooling water system and a reduction in the coolant system’s flow rate due to significant debris influx into the intake structure, leading to manual shutdown of the reactor. | Kori 4 |
| 2003 | A fault on the transmission line resulted in the opening of the circuit breaker, followed by a low flow signal of the reactor coolant, prompting the reactor shutdown. | Kori 3 |
| 2003 | A fault on the transmission line resulted in the opening of the circuit breaker, followed by a low flow signal of the reactor coolant, prompting the reactor shutdown. | Kori 4 |
| 2003 | The salt accumulation on the current transformer suspension insulator was dislodged, causing a fault in the transmission line, and the reactor shuts down due to the transmission line failure. | Kori 1 |
| 2003 | The salt accumulation on the current transformer suspension insulator was dislodged, causing a fault in the transmission line, and the reactor shuts down due to the transmission line failure. | Kori 2 |
| 2003 | The dislodged debris from the insulation composite panel, having detached from the turbine building roof, collided with the high-pressure side of the adjacent condenser, resulting in a fault and subsequent activation of the differential relay to protect the adjoining condenser. Consequently, the turbine and generator were brought to a halt. | Wolsong 2 |
| 2018 | The activation of the white emergency wind speed alarm and the illumination of the white emergency wind speed beacon led to the declaration of a white emergency. | Hanul 1 |
| 2018 | The activation of the white emergency wind speed alarm and the illumination of the white emergency wind speed beacon led to the declaration of a white emergency. | Hanul 3 |
| 2020 | During the typhoon, the jumper line connecting the power transmission line and the distribution line and the steel tower suffered insulation breakdown and momentary flashover due to severe shaking. The flashover caused a fault in the power transmission line and the distribution line, leading to the opening of the switchyard circuit breaker and resulting in the loss of off-site power. Consequently, the reactor automatically shuts down due to the cessation of the reactor coolant pump. | Shin Kori 1 |
| 2020 | During the typhoon, the jumper line connecting the power transmission line and the distribution line and the steel tower suffered insulation breakdown and momentary flashover due to severe shaking. The flashover caused a fault in the power transmission line and the distribution line, leading to the opening of the switchyard circuit breaker and resulting in the loss of off-site power. Consequently, the reactor automatically shuts down due to the cessation of the reactor coolant pump. | Shin Kori 2 |
| 2020 | The deterioration of insulation strength caused by the seawater intrusion led to a flashover in the instrument current transformers of the surrounding pressure vessels and the supporting insulators of the busbars. This flashover caused a power outage in the off-site power lines, resulting in a low-voltage condition. | Kori 1 (decommissioning) |
| 2020 | The deterioration of the insulation strength caused by the seawater intrusion led to flashovers in the lightning arresters of instrument transformers and start-up transformers. This, in turn, caused the opening of the switchyard circuit breakers, leading to the subsequent shutdown of the turbine generators and the reactor. Additionally, the emergency diesel generators were activated. | Kori 3 |
| 2020 | The deterioration of insulation strength caused by the seawater intrusion led to a flashover in the instrument current transformers of the surrounding pressure vessels and the supporting insulators of the busbars. This resulted in a power outage in the off-site power lines, leading to a low-voltage condition. | Kori 2 |
| 2020 | Seawater intrusion led to a flashover in the lightning arresters of the instrument transformers in the control room and the start-up transformers, triggering the circuit breakers in the switchyard to trip and cause the shutdown of the turbine generator and the reactor. In response, the emergency diesel generator was activated. | Kori 4 |
| Year | Detailed information on the incidents |
|---|---|
| 1998 | In response to the hurricane, the power plant declared an abnormal situation and initiated a shutdown. Preparations for the plant’s response strategy to the hurricane’s approach were finalized, and the onsite emergency response equipment was activated. After the hurricane passed, the investigation indicated no personnel or physical damage. |
| 2004 | Following the passage of the hurricane with wind speeds of 105 miles/hr and, subsequently, the second storm, with winds of 120 miles/hr, the nuclear power plant experienced a loss of off-site power. |
| 2005 | In response to the hurricane approach alert for the hurricane, the power plant promptly executed its emergency response procedures and performed a safe shutdown. |
| 2007 | While operating at 14% of its rated output, the turbine generator tripped due to the closure of the 345 kV transmission line circuit breakers. The trip was triggered by an electrical fault at the transmission line insulator of the 345 kV steel tower located between the surrounding pressurizer and the 345 kV switchyard. |
| 2012 | Under normal operating conditions, the hurricane led to an automatic shutdown of the turbine generator and reactor as a result of the interruption of the 345 kV transmission line. |
| 2013 | The hurricane resulted in the shutdown of the nuclear power plant due to the loss of circulation pumps. |
| 2013 | The automatic shutdown of the turbine and reactor was triggered by the operation of the protective differential relay caused by a fault (short circuit) on the 345 kV transmission line. |
| 2014 | The obstruction of the turbine building’s cooling water system heat exchanger by debris during a typhoon led to a loss of power generation. The cause was identified as foreign matter larger than the strainer openings. |
| 2016 | Operating at 220 MWe output under an off-load condition, the high-voltage cables connected to the busbars and surrounding generators sustained damage, resulting in the isolation of the turbine generator from the grid. |
| 2017 | The reactor underwent a shutdown owing to issues with the switchyard. Salt accumulation was detected on the insulators of the ring bus, leading to a busbar lockout on the eastern switchyard and a disruption in power supply. |
| 2018 | The power plant’s 500 kV off-site power grid suffered a transmission line failure and damage to the switchyard equipment caused by a powerful typhoon exceeding the design criteria. |
| 2020 | The nuclear power plant operators declared an abnormal condition in accordance with the procedural guidelines in response to a hurricane. |
The majority of damage incidents resulting from typhoons at nuclear power plants were attributed to indirect rather than direct effects. Among the Korean nuclear power plants, the Kori Nuclear Power Plant, located on the southern coast of the East Sea, experienced the highest number of typhoon-related damages. Both Korean and international typhoons primarily affected the power grid of nuclear plants. Drawing from the typhoon damage cases, Table 7 provides a comprehensive summary of the major types of damages that can significantly affect the stable operation of nuclear power plants.
| Types of damage from typhoons | |
|---|---|
| 1 | Strong wind pressure can put substantial strain on structures and external facilities, which can cause functional and structural damage to vulnerable equipment and areas. |
| 2 | External facilities may be susceptible to potential missile strikes, which could lead to the loss of ventilation systems and loss of off-site power. |
| 3 | Strong winds can shake unsecured metallic objects, which could come into contact with high-voltage lines, resulting in short circuits. |
| 4 | Strong winds can result in a substantial amount of seaweed and debris entering the intake structure, potentially causing interruptions in the coolant supply or impairing the functionality of the cooling water system. |
| 5 | The accumulation of saltwater salinity on busbars, switchgear, and other electrical equipment can significantly affect their functionality, leading to long-term corrosion and malfunctions. |
| 6 | Damage to the off-site power distribution system equipment can disrupt the external power supply. |
| 7 | The damage to the external communication equipment and the closure of access roads may result in the loss of communication with external agencies. |
| 8 | Strong winds and heavy rainfall can potentially cause secondary damage, such as landslides, leading to consequential impacts. |
Furthermore, typhoons can lead to secondary damage at nuclear power plants through missile strikes. Missiles, comprising external objects such as building materials, rocks, trees, metal poles, and fragments, can be propelled by intensified wind loads, resulting in structural damage [49]. The behavior of missiles is primarily governed by factors such as its initial placement, travel distance, dimensions, and wind speed [44, 50]. Consequently, missiles can impinge upon the shielding and access points, causing damage to windows and doors and potentially leading to the loss of ventilation systems and an external power supply. Table 8 illustrates the missile impact on nuclear plant structures, systems, and components induced by typhoons.
| Classification | SSCs | Main failure mode |
|---|---|---|
| Structures | Turbine building | Roof and wall panel detachment caused by wind pressure |
| Off-site power system | Transmission tower | Transmission tower collapsed by gusts of strong winds |
| Off-site transformer | Missile strikes/fire | |
| Auxiliary feedwater system | Condensate storage tanks | Penetration by missiles |
| Coolant system | Component cooling water heat exchanger | Secondary damage by crane collapse |
| Essential cooling water pump | Missile strikes | |
| Emergency power system | Emergency diesel generator fuel oil storage tank | Penetration by missiles |
| Others | Yard crane | Collapse by wind pressure |
The climate is expected to lead to an increase in the intensity of typhoons, posing potential safety risks to nuclear power plants. Therefore, ensuring the safe operation of these plants necessitates a thorough assessment of typhoon risk events and the improvement of the resilience of vulnerable equipment. A critical aspect involves evaluating the typhoon hazard level while accounting for climate change and reevaluating the design wind speed. Additionally, steps must be taken to address the missiles generated by typhoons. This involves the removal of potential missiles, such as rocks, metal columns, wooden beams, and external building materials, from the vicinity of the plant site. Furthermore, strategic planning should ensure sufficient distance between major structures and equipment to minimize the strike of flying missiles. Should missiles come into contact with critical targets, protective measures should be in place to prevent penetration. Implementing these measures can significantly enhance the safety of nuclear power plants against typhoon events.
3.2.2. Heavy Rainfall
Climate change is anticipated to lead to the intensification of tropical cyclones, resulting in stronger winds and an increased occurrence of localized heavy rainfall. Consequently, nuclear power plants face an increased risk of external flooding. In order to evaluate the potential effect of concentrated rainfall on these facilities, instances of damage to both Korean and international nuclear power plants have been compiled and presented in Tables 9 and 10, respectively.
| Year | Detailed information on the incidents | Unit |
|---|---|---|
| 1980 | The heavy rainfall led to water leakage in the turbine hall, triggering the turbine protection relays and resulting in the subsequent shutdown of the turbine generator and reactor. | Kori 1 |
| 1991 | Heavy rainfall and lightning caused a malfunction in the transmission network, causing an abnormal increase in system frequency and turbine rotational speed. This triggered the turbine overspeed protection mechanism, resulting in the shutdown of the turbine generator and reactor. | Kori 1 |
| 2014 | Heavy rainfall caused flooding in the circulating water pump room, resulting in the manual shutdown of the turbine and the automatic shutdown of the reactor. | Kori 2 |
| Year | Detailed information on the incidents |
|---|---|
| 1999 | The hurricane caused high waves accompanied by strong winds, leading to flooding within the nuclear power plant site. |
| 2008 | A malfunction in the drainage system resulted in water ingress into the auxiliary building of the nuclear reactor. |
| 2011 | The nuclear power plant site was flooded by heavy rainfall. |
| 2013 | The hurricane resulted in strong winds and torrential rains, with wind speeds exceeding 55 mph, leading to a power outage. |
| 2014 | In a high-temperature atmospheric condition at the power plant, strong winds and heavy rain led to a power outage in the 4.16 kV switchgear. |
Heavy rainfall can result in water ingress into critical infrastructure within the nuclear power plant site, thereby leading to functional impairments. Moreover, nuclear power plants close to rivers or dams are vulnerable to flooding triggered by heavy rainfall events. Therefore, to prepare for external flooding, a precise and thorough assessment of the risk of such occurrences is of paramount importance. Equally crucial is the effective implementation of measures designed to prevent water ingress along potential pathways.
3.2.3. Sea Level Rise
As of 2023, about one-fourth of the approximately 440 operational nuclear power plants worldwide (as shown in Figure 1) are located along coastlines. Many of these plants were initially constructed at elevations ranging from approximately 10 to 20 meters above sea level when climate change was not widely recognized as a significant threat. However, with the current rise in sea levels, there is an increased potential for large-scale natural disasters, such as tsunamis, which raises the likelihood of external events affecting nuclear power plants. As a result, it becomes imperative to carefully consider the potential impacts of sea level rise on these facilities. Table 11 provides instances of nuclear plant damage caused by sea level rise.
| Year | Detailed information on the incidents |
|---|---|
| 1980 | A rising water level resulted in groundwater contaminating the wastewater storage tank. |
| 2000 | The diesel building flooded due to inadequate site drainage, leading to the malfunctioning of three emergency power supply systems and the subsequent shutdown of the reactor. |
| 2004 | The tsunami-induced sea level rise caused the water level on the site to exceed 1.9 meters, surpassing the usual depth of 3 meters or less. Consequently, the operating switch of the seawater pump room was submerged, leading to the shutdown of the CCW pump (condenser cooling water pump) and subsequent reactor shutdown. |
| 2011 | The tsunami caused flooding of the emergency diesel generator, leading to the shutdown of the nuclear power plant. |
| 2011 | A massive earthquake triggered a seismic tsunami, reaching a height of 15 meters, which inundated the nuclear power plant and inflicted substantial damage on its internal and external electrical facilities. |
Sea level rise itself may not directly affect nuclear power plants. However, research indicates that extreme events, such as tsunamis, storm surges, and meteorological tsunamis that exceed the plant’s design criteria, can significantly elevate the risk of flooding. The consequences of tsunamis can be multifaceted, encompassing site inundation, submergence of facilities, equipment damage due to powerful wave forces, and potential malfunctions or reduced capacity of water intake systems [44]. Additionally, tsunamis can affect water intake facilities by depositing sand and debris [52]. Therefore, a comprehensive assessment is essential to reevaluate the design basis, taking into account the potential increases in maximum water levels at nuclear power plant sites due to typhoons and seismic tsunamis [44]. To address the potential flooding of emergency power systems and critical safety equipment, installing flood-resistant doors and watertight drainage pumps and incorporating seismic-resistant design features is recommended.
3.2.4. Seawater Temperature
Nuclear power plants commonly rely on seawater as a coolant within the reactor vessel [53]. The coolant system of a nuclear power plant comprises both the safety-related primary side cooling water system and the non-safety-related secondary side cooling water system. An increase in seawater temperature signifies a rise in the intake temperature of the cooling water, which can have implications for the safety of the nuclear power plant. If the seawater temperature exceeds the maximum design temperature of the plant, it can lead to a situation of ultimate heat sink loss. With global climate change driving a steady increase in seawater temperatures, adjustments have been made to raise the ultimate heat sink design temperature for Shin Kori units 3 and 4. Table 12 presents examples of the events of rising seawater temperatures on nuclear power plants.
| Year | Detailed information on the incidents |
|---|---|
| 2010 | The nuclear reactor power level was reduced to 92% due to a high coolant inlet temperature. |
| 2010 | The nuclear reactor power level experienced successive reductions for over a month due to the high lake water temperature at the intake structure. |
| 2010 | The nuclear reactor power level experienced a decrease to 97% for approximately 5 hours as a result of the high intake water temperature. |
| 2010 | Over the course of a month, the nuclear reactor power level experienced multiple reductions due to high river water temperatures, causing increased back pressure in the condenser. |
| 2010 | The nuclear reactor power level experienced successive reductions for over a month due to the high lake water temperature at the intake structure. |
| 2010 | The condensate polisher’s increased temperature resulted in a reduction in the reactor’s power output. |
| 2010 | The nuclear reactor power level experienced successive reductions due to the high lake water temperature at the intake structure. |
| 2010 | The heightened river water temperature in the intake structure caused an upsurge in back pressure in the condensate polisher, resulting in a reduction of reactor power output from 95% to 88%. |
| 2010 | In response to the elevated river water temperature in the intake structure, the reactor power output was periodically reduced for a duration of one month to ensure the condenser temperature stayed below 130 degrees Fahrenheit. |
| 2011 | In order to stay within the temperature limit of 32 degrees Fahrenheit, the reactor power output was reduced to 89%. |
| 2012 | To adhere to the temperature limit set by the national pollutant discharge elimination system (NPDES) for effluent discharge, the reactor power output was reduced to 80%. |
| 2012 | The increased ambient temperature resulted in a high condensate system temperature, causing a temporary reduction in reactor power output to 96% for approximately 5 hours. Subsequently, the reactor’s power output was restored to 100%. |
| 2012 | The high temperature of the lake water at the intake structure caused a reduction in the nuclear reactor power level. |
| 2013 | The high ambient temperature, caused by the elevated seawater intake temperature approaching the limit of 75 degrees Fahrenheit, resulted in a reduction in reactor power output. |
| 2013 | The reactor power output was reduced due to the increase in cooling water temperature caused by warm weather conditions. |
| 2015 | The elevated ambient temperature caused a high temperature in the condenser, reducing the reactor’s power output. |
| 2019 | The nuclear power plant underwent a shutdown due to the constant high temperatures, resulting in the water temperature reaching 25°C. |
Water temperature has been found to cause a reduction in reactor power in nuclear power plants. While this temperature does not directly impinge upon the safety systems, such as safe shutdown and core cooling mechanisms, it does have implications for the plant’s overall operational performance [44]. Hence, ensuring the plant’s stable operation necessitates the maintenance of the water temperature within specified design limits. This can be achieved through additional pump and heat exchanger operation measures, as well as limitations on the operation of nonessential equipment to regulate the temperature rise. Given the ongoing climate change and the consequent increase in water temperatures, continuous monitoring and periodic evaluation of the effectiveness of the ultimate heat removal system become crucial for maintaining the plant’s operational stability.
3.2.5. Marine Organisms
Climate change has led to an influx of marine organisms, which has led to frequent power plant shutdowns, resulting in external events on power plants along the coast. Tables 13 and 14 provide a compilation of Korean and international cases of power plant shutdowns resulting from the ingress of marine organisms [31].
| Year | Detailed information on the incidents | Unit |
|---|---|---|
| 1988 | The ingress of Gasterosteus aculeatus swarms into the intake canal resulted in a manual shutdown of the reactor. | Kori 4 |
| 1988 | The ingress of Gasterosteus aculeatus led to the shutdown of the reactor and turbine. | Kori 4 |
| 1991 | The ingress of a jellyfish swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 2 |
| 1996 | The ingress of a shrimp swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 1 |
| 1997 | The ingress of a shrimp swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 2 |
| 1997 | The ingress of a shrimp swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 1 |
| 1997 | The ingress of a shrimp swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 2 |
| 1997 | The influx of shrimp swarms led to the manual tripping of the reactor. | Hanul 1 |
| 1997 | The influx of shrimp swarm led to the manual tripping of the reactor. | Hanul 2 |
| 2001 | The ingress of a shrimp swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 1 |
| 2001 | A shrimp swarm influx caused the reactor to experience subcriticality. | Hanul 1 |
| 2001 | The ingress of a jellyfish swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 2 |
| 2001 | The ingress of a jellyfish swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 2 |
| 2006 | The ingress of a jellyfish swarm into the intake canal resulted in the reactor’s shutdown. | Hanul 1 |
| 2006 | The ingress of marine organisms led to the manual shutdown of the turbine/generator. | Hanul 1 |
| 2006 | The ingress of marine organisms led to the manual shutdown of the turbine/generator. | Hanul 2 |
| 2021 | The influx of marine organisms (salpa) through the intake structure triggered the automatic operation of the auxiliary feedwater system. | Hanul 1 |
| 2021 | The ingress of marine organisms (salpa) through the intake structure led to the automatic shutdown of the reactor. | Hanul 2 |
| 2021 | The ingress of marine organisms (salpa) led to the manual shutdown of the turbine/generator. | Hanul 1 |
| 2021 | The ingress of marine organisms (salpa) led to the manual shutdown of the turbine/generator. | Hanul 2 |
| Year | Detailed information on the incidents |
|---|---|
| 1988 | The ingress of a Gasterosteus aculeatus swarm into the intake canal resulted in the manual shutdown of the reactor. |
| 1991 | The ingress of seaweed resulted in damage to the waste treatment facility. |
| 1995 | The ingress of currents halted the circulation water pump, leading to the suspension of four units. |
| 1997 | The ingress of jellyfish resulted in damage to the waste retrieval basket. |
| 1999 | The cooling water pump experienced cavitation, leading to the suspension of one unit and causing damage. |
| 2001 | The ingress of green algae (Cladophora) resulted in the suspension of two units from operation. |
| 2005 | The ingress of jellyfish caused the cooling water pump to stop and reduce its output. |
| 2006 | Phytoplankton and small fish ingress caused the breaking of the traveling screen pins. |
| 2007 | The inflow of seaweed caused the shutdown of circulating water pumps and facilities. |
| 2007 | A large quantity of shellfish obstructed the condenser, resulting in its operational suspension. |
| 2008 | The ingress of jellyfish led to the shutdown of one unit and a reduction in output for another unit. |
| 2011 | The ingress of jellyfish resulted in reduced generator output. |
| 2012 | The ingress of salpa through the intake structure resulted in the shutdown of the nuclear power plant. |
| 2018 | The ingress of green algae (Cladophora) led to the tripping of the cooling water pump, resulting in the suspension of four units from operation. |
| 2020 | Fish ingress caused the drum screen to malfunction, leading to the tripping of the cooling water pump. |
Numerous incidents involving reduced output, turbine/generator shutdowns, and reactor shutdowns in nuclear power plants have been linked to the intrusion of marine organisms. Organisms such as anchovies, shrimps, jellyfish, large spiny fish, and salpa can attach to the screens installed in the seawater intake system, intended to prevent the ingress of foreign material, thereby obstructing the inflow of circulating water and impacting the operation of nuclear power plants [54, 55]. As of now, the ingress of marine organisms has not compromised the safety of nuclear power plants. However, marine organisms entering unexpectedly into the intake structure can render the operation of the circulating water pumps infeasible, requiring significant time for recovery. Furthermore, the frequency of plant shutdown incidents triggered by the ingress of marine organisms cannot be underestimated, as they can also disrupt the primary cooling water system. Consequently, it becomes imperative to implement measures for the early detection of marine organism ingress through research, probabilistic safety assessments, and other safety analyses.
3.2.6. Wildfire
The magnitude and frequency of wildfire incidents are on the rise, which can be attributed to factors such as rising temperatures and decreasing humidity. These wildfires often erupt in nearby forests, ignited by natural sources such as lightning strikes, agricultural activities, open burning, and deliberate fires, posing a significant threat to nuclear power plants. This is particularly relevant in South Korea, where a significant portion of the national territory comprises forested areas and several nuclear power plants are situated near these forests. Instances of nuclear power plant damage caused by wildfires are documented in Table 15.
| Year | Detailed information on the incidents | Unit |
|---|---|---|
| 2000 | The nuclear power plant was forced to shut down after wildfires disrupted transmission lines and caused a high neutron flux rate in external neutron detectors. | Hanul 1 |
| 2000 | The nuclear power plant encountered a gradual decline in turbine speed caused by a reduction in power output due to transmission line disconnection, leading to the plant’s shutdown. | Hanul 2 |
| 2022 | A wildfire in the Ulsan region caused an interruption in some peripheral transmission lines, resulting in a voltage drop in the nuclear power plant’s off-site power system and safety bus. | Hanul 6 |
Nuclear power plants have experienced shutdowns as a consequence of wildfires, specifically due to loss of off-site power disruptions. Moreover, forest fires can simultaneously affect multiple nuclear power plants [44]. Therefore, when conducting safety evaluations of nuclear power plants located near forested areas, it is crucial to quantitatively consider the impact of a forest fire on off-site power networks, plant systems, equipment, and operators. This can be achieved using logical models such as fault and event trees [44].
4. Conclusion and Policy Implications
Climate change is resulting in a rise in atmospheric and seawater temperatures, increased rainfall intensity, heightened storm intensity, and elevated sea levels. Consequently, there have been notable alterations in the magnitude and frequency of natural hazards such as strong winds (typhoons), heavy rainfall, wildfires, droughts, and extreme weather events. Therefore, the frequency and intensity of external events that may affect nuclear power plants must be altered. Presently, the safety of nuclear power plants is being considered in relation to climate change, with both direct and indirect considerations. Safety guidelines are devised to account for natural hazards such as typhoons, heavy rainfall, and sea level rise. However, it is crucial to recognize that climate change is a long-term phenomenon rather than a short-term change, thereby necessitating the safe operation of nuclear power plants in the face of natural hazards. Therefore, this study is aimed at investigating and analyzing the potential implications of climate change on nuclear power plants, particularly in relation to external events triggered by weather phenomena associated with climate change. The objective was to enhance the preparedness of nuclear power plants in the face of climate change.
Based on the current findings, it has been observed that climate change-induced external events have predominantly resulted in minor incidents, such as temporary shutdowns, rather than significantly compromising the safety of nuclear power plants. However, it is essential to acknowledge that the intensity and frequency of these external events may vary depending on the specific location of the plant. Therefore, site-specific measures are imperative to address the potential impacts of climate change on the safety and operation of nuclear power plants. The safety assessment of nuclear power plants can be approached through deterministic and probabilistic methods. Deterministic assessments generally demonstrate that nuclear power plants are designed to have notably high levels of safety and resilience compared to other industrial facilities, with multiple systems and redundancies in place to mitigate accidents. However, from a probabilistic standpoint, climate change may reduce the safety margins of various systems and structures, ultimately elevating the risk profile of nuclear power plants. As a result, it is crucial to emphasize that, in terms of risk assessment, climate change-related accidents are likely to stem from failures in lower-grade safety systems that may propagate to higher-grade safety systems. One particularly concerning aspect is the external power grid’s vulnerability, which can be exacerbated by climate change, posing significant risks to the safety and operation of nuclear power plants. Although extensive documentation of the substantial impacts of climate change on nuclear power plants is limited, the rapid pace of climate change necessitates continuous research and analysis. For instance, ensuring the validity of determining design basis loads demands consideration of the intensity and frequency of natural hazards associated with climate change. Given the dynamic nature of climate change, relying solely on historical data may not suffice. Furthermore, developing robust methodologies to quantify risks associated with various external events resulting from climate change is of utmost importance, as current frameworks primarily focus on seismic events. Expanding the range of risk quantification techniques to encompass a broader spectrum of external events linked to climate change is crucial for comprehensive safety assessments of nuclear power plants.
Disclosure
This is an Open Access article distributed under the terms of the Creative Commons Attribution Noncommercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (Ministry of Science and ICT) (No. RS-2022-0015457). And also, this work was supported by the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety (KoFONS), granted financial resources from the Nuclear Safety and Security Commission (NSSC), Republic of Korea (RS-2024-00404119).
Open Research
Data Availability
Only partial data is available on request.
