The IAEA sounds the alarm – Nuclear fear in Europe: How critical is the situation at the Zaporizhzhia nuclear power plant in Ukraine?
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Published on: October 5, 2025 / Updated on: October 5, 2025 – Author: Konrad Wolfenstein
The IAEA sounds the alarm – Nuclear fears in Europe: How critical is the situation at the Zaporizhzhia nuclear power plant – Creative image: Xpert.Digital
The Zaporizhzhia Nuclear Power Plant – An Analysis of the Current Security Situation
### Zaporizhia on the brink: Only 10 days of diesel left – what's the danger when the lights go out? ### No electricity, no cooling: The horror scenario of a nuclear meltdown in Zaporizhia ### "Station Blackout": Why the emergency power generators in Zaporizhia are becoming a time bomb ###
A second Chernobyl? The 5 biggest threats to the Zaporizhzhia nuclear power plant
The situation at the Zaporizhzhia Nuclear Power Plant, Europe's largest nuclear facility, has escalated dramatically. For over a week, the plant has been completely cut off from external power supplies – an unprecedented and highly dangerous situation in the plant's history. The entire safety of the six reactors now hangs in the balance: Eight emergency diesel generators are the only remaining source of power to maintain vital fuel cooling.
But this emergency solution is a ticking time bomb. According to the power plant management appointed by Moscow, the diesel reserves on site are only sufficient for about ten days. The generators, which are not designed for continuous operation, are running at extremely high loads, and the first units have already failed. The International Atomic Energy Agency (IAEA) is deeply concerned and describes the generators as the "last line of defense" against a potential catastrophe. If this last bastion fails, there is a risk of a complete power outage – a so-called "station blackout" – which could lead to a nuclear meltdown with an uncontrollable release of radioactivity within hours. This text analyzes the acute threat, explains the technical risks of a prolonged power outage, and sheds light on the catastrophic consequences a nuclear accident would have for Ukraine and all of Europe.
What is the current situation at the Zaporizhzhia nuclear power plant?
Since September 23, 2025, the Zaporizhzhia Nuclear Power Plant, Europe's largest nuclear facility with six reactors, has been in a critical situation. Following sustained fighting, the plant has been without a regular external power supply for more than a week—an unprecedented situation in the plant's history. This represents the longest power outage during the more than three and a half years of hostilities.
Cooling of the fuel rods currently depends exclusively on eight diesel emergency generators. The power plant remains under the control of Russian occupation forces and a Moscow-appointed plant management. Russian forces occupied the facility shortly after the start of the war of aggression in spring 2022 and have held it ever since.
How long can the emergency generators supply the power plant?
According to the power plant management appointed by Moscow, the diesel reserves on site are sufficient for about another ten days. This period is maintained by regular fuel deliveries. However, the generators are not designed for continuous operation and operate at high loads. This emergency solution carries significant risks, as the generators are not designed for long-term operation.
The first generators have already failed and urgently require repairs. Ukrainian President Volodymyr Zelenskyy warned in his late-night video message that one of the diesel generators is no longer functioning. Any further malfunction could have fatal consequences.
What does the International Atomic Energy Agency say about the current situation?
The International Atomic Energy Agency (IAEA) is concerned about the developments at Zaporizhzhia. IAEA Director General Rafael Mariano Grossi stated on September 30, 2025: "The power plant is currently operating thanks to its backup diesel generators—the last line of defense—and there is no imminent danger as long as these continue to operate. Nevertheless, this is clearly not a sustainable situation from a nuclear safety perspective."
Grossi further emphasized: "Neither side would benefit from a nuclear accident." He strongly encouraged both warring parties to cooperate with the IAEA to facilitate the crucial repairs. "It is extremely important that the external power supply is restored."
The IAEA described the emergency diesel generators as a "last line of defense" that should only be used in extreme situations. The current condition of the reactor units and spent fuel will remain stable as long as the emergency diesel generators can provide sufficient power to maintain essential safety functions and cooling.
What technical risks exist in the event of a prolonged power outage?
At the heart of every nuclear power plant are fuel rods that generate large amounts of heat through nuclear fission—not only during operation, but also after the reactor is shut down. This is caused by decay heat: radioactive elements in the fuel rods continue to decay, releasing energy in the process.
The decay heat decreases only gradually after the reactor is shut down. After one hour, it amounts to approximately 1.6 percent of the heat output during normal operation, one day after shutdown, it amounts to 0.8 percent, and several months after shutdown, it remains at approximately 0.1 percent of the output. This heat must be continuously dissipated.
To safely dissipate this dangerous heat, the water in the reactor must be continuously circulated. If cooling is not provided, the temperature rises rapidly. At temperatures above approximately 1200 degrees Celsius, the metal cladding of the fuel rods melts, threatening the release of radioactive substances. Continuous cooling is therefore a key safety feature. Even after shutdown, the fuel elements must remain cooled for many days.
What happens if there is a complete power failure?
If the external power supply fails, diesel generators automatically take over supplying the cooling pumps. Most nuclear power plants are designed to provide emergency power for a maximum of ten days – provided the equipment and fuel are available. The generators operate at high load and require a regular supply of diesel.
If the entire emergency power supply fails—a so-called "station blackout"—batteries and uninterruptible power supplies act as a last resort for a few hours. Within this critical time window, attempts are made to shut down the reactor as quickly as possible by inserting control rods and connecting mobile generators from outside.
If cooling continues, the temperature in the reactor core and fuel pools begins to rise rapidly. After a few hours, so-called "dryout" zones develop: the fuel rods are partially dry, threatening cracks and material damage. If this condition persists, a core meltdown occurs – the radioactive material melts away and can escape unhindered into the environment.
What would be the consequences of a nuclear disaster?
An emergency depressurization could release large quantities of radioactive aerosols and gases. The consequences would be regional, and possibly even transboundary, radioactive contamination. There is a risk of death from radiation sickness and long-term consequences such as increased cancer rates in the affected area.
The release of radioactive material into the vicinity of the power plant can have dramatic consequences for people and the environment. Short-term radiation exposure of 0.25 sieverts can cause radiation sickness. Symptoms include headaches, nausea, and vomiting. If exposure rises to 4 sieverts, the illness can be fatal.
In the long term, people living in contaminated areas have a significantly increased risk of cancer. Thyroid cancer, leukemia, and solid tumors are particularly common. The radioactive material can seep through the soil and contaminate many square kilometers of soil and plants. If no monitoring measures are taken, it can also enter the food chain of humans and animals.
Evacuations and emergency measures would then affect not only the population in the immediate vicinity, but also cities and countries hundreds of kilometers away. As determined by the Max Planck Institute for Chemistry in Mainz, half of the radioactive cesium-137 would be transported more than 1,000 kilometers in such a worst-case scenario.
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How comparable would the effects be to Chernobyl or Fukushima?
The reactors in Zaporizhia are Western-style pressurized water reactors. The risk of a nuclear explosion is lower with this type of reactor than with other types. The reactors have containment—a protective shell around the reactor core, which did not exist at Chernobyl.
The Chernobyl accident of April 26, 1986, was due to the reactor's design. It was constructed in such a way that, under certain circumstances, the nuclear chain reaction could escalate uncontrollably. Within seconds, the reactor reached several hundred times its designed maximum power. Furthermore, due to its design, the reactor contained large amounts of graphite, which ignited and burned for several days.
The graphite fire carried significant amounts of released radioactivity to great heights, thus causing the widespread dispersal of radioactive substances. In Fukushima, however, it was pressurized water reactors similar to those in Zaporizhzhia. There, too, the failure of the cooling systems was the primary cause of core meltdowns in three reactors.
What preventive measures are common internationally?
The IAEA Safety Standards represent the international consensus on what constitutes a high level of safety to protect people and the environment from the harmful effects of ionizing radiation. These standards are divided into three categories:
The Safety Fundamentals define the basic safety objective and the principles of protection and safety. The Safety Requirements establish an integrated and consistent set of requirements that must be met to ensure the protection of people and the environment. The Safety Guides provide recommendations and guidance for compliance with the safety requirements.
Modern Western nuclear power plants generally take core meltdowns into account during design and configure secondary safety systems to ensure a safe outcome even if the safety measures intended to prevent a meltdown fail. This is increasingly moving away from "active" safety and toward "passive" safety, which functions even when humans cannot intervene.
How likely are nuclear accidents statistically?
Scientists at the Max Planck Institute for Chemistry in Mainz have calculated, based on the operating lives of all civilian nuclear reactors worldwide and the number of core meltdowns that have occurred, that such events can occur in the current power plant inventory approximately once every 10 to 20 years. This is 200 times more frequent than previously estimated.
The researchers also determined that Western Europe – including Germany – will likely be exposed to more than 40 kilobecquerels of radioactive cesium-137 per square meter once every 50 years. According to the IAEA, this level is considered radioactively contaminated. The results demonstrate that Western Europe faces the world's highest risk of radioactive contamination from severe reactor accidents.
What special challenges exist in times of war?
The situation in Zaporizhzhia is particularly precarious due to the ongoing war. Due to fighting near the power plant, both Russia and Ukraine have declared themselves unable to repair the damaged power lines. According to Ukrainian sources, Russian shelling has cut the plant off the power grid, while Moscow blames Ukrainian shelling.
The Ukrainian Energy Ministry called on the country's international partners to put pressure on Russia to bring the plant back under Ukrainian control. Greenpeace accused Moscow of sabotaging the pipeline in order to connect Zaporizhia to the Russian grid and restart the reactors.
Before the war, ten external power lines were available. Currently, the power plant relies on a single external line. Furthermore, the water level in the cooling pond has dropped by more than 3.2 meters since the destruction of the downstream Kakhovka Dam in June 2023.
What role do international observers play on site?
IAEA observers are on site and monitoring safety. IAEA Chief Grossi has held multiple talks with both warring parties to defuse the situation at the nuclear power plant. The IAEA team on site regularly reports on the condition of the facility and conducts inspections of various areas.
However, according to the IAEA, the on-site team is not granted sufficient access to all areas of the power plant. Observers confirmed that all twelve sprinkler ponds, which receive water from groundwater wells and, among other things, provide water for cooling the reactors and spent fuel, are full.
What are the next critical points?
The critical phase has already arrived. With every day that the external power supply is not restored, the risk of a serious incident increases. Diesel reserves are sufficient for about ten more days, but the first generators have already failed.
A reliable power supply is essential for the safe operation of the plant, as it maintains cooling and safety systems that prevent reactor core meltdowns and thus a nuclear accident. If no quick solution is found to restore the external power supply or at least reliably maintain and supply the emergency generators with fuel, the situation could worsen dramatically.
The international community is monitoring the situation with growing concern, as a nuclear incident could affect not only the region but also large parts of Europe. The IAEA is in constant contact with both warring parties with the goal of facilitating a rapid reconnection of the power plant to the power grid.
What are the long-term implications of the crisis for nuclear safety?
The situation in Zaporizhia demonstrates the particular risks of nuclear power plants in war zones. With its attacks on nuclear facilities, Russia has violated the Geneva Protocol and IAEA resolutions, and thus international law. This sets a dangerous precedent for future conflicts.
The ongoing crisis highlights the limitations of the international nuclear safety architecture. Although IAEA safety standards provide comprehensive provisions for various accidents, the challenges of armed conflict are addressed only to a limited extent.
The events in Zaporizhia will likely lead to a revision of international safety standards to create better provisions for the protection of nuclear facilities in times of conflict. The IAEA is already working on a long-term strategy to further develop safety standards, including optimizing the interfaces between safety and security.
The crisis also underscores the need for increased international cooperation in protecting critical infrastructure and demonstrates how vulnerable even highly secure technical systems are in times of armed conflict. The lessons from Zaporizhia will have a lasting impact on the debate about the future of nuclear energy and nuclear safety requirements.
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