The diesel generators, which have been ensuring the safety of Europe’s largest nuclear power plant since September 23, are the last line of defense for the NPP. Is a “second Chornobyl” possible if they fail or if Russia tries to “ramp up” one of the shutdown reactors?

Contents

1. What is happening at the Zaporizhzhia Nuclear Power Plant?
2. Why Russia needs a blackout at the Zaporizhzhia Nuclear Power Plant
3. Is a Chornobyl or Fukushima scenario possible?
4. After connecting the plant to its power lines, Russia may try to start a reactor
5. How the IAEA and the EU are reacting to the situation

What is happening at the Zaporizhzhia Nuclear Power Plant?

The Zaporizhzhia Nuclear Power Plant is the largest in Europe and one of the five largest in the world. It has six VVER-1000 power units, each with a capacity of 1000 MW. In early March 2022, Enerhodar was occupied, and the Zaporizhzhia Nuclear Power Plant came under Russian control. Gradually, all power units were transferred to a so-called cold shutdown – meaning the nuclear fuel is not active, and the plant does not produce electricity. However, the fuel itself still heats up gradually, and to maintain a safe temperature of 30-35°C, the plant needs electricity. Thus, from being the largest producer of electricity, the ZNPP has turned into a consumer. 

Until May 2025, the Zaporizhzhia Nuclear Power Plant could receive electricity from the Ukrainian power grid through two transmission lines: Dniprovska 750 kV and Ferosplavna-1 330 kV. At the end of May, IAEA Director General Rafael Grossi reported that the plant was receiving electricity from only one line because the 330 kV line was damaged. And since September 23, the ZNPP has lost power from the Dniprovska line as well. The Russian Federation blamed a “Ukrainian drone” for this, and the plant switched to power from diesel generators. 

Such blackouts have happened at the ZNPP before. This is the 10th one. However, until now, Ukrainian energy workers quickly restored the damaged lines, and the plant switched back to normal power supply. But now the damage is in the territory controlled by the invading Russian forces, and they are not repairing it.

Why Russia needs a blackout at the Zaporizhzhia Nuclear Power Plant

Mykhailo Shuster, former director of procurement at Energoatom, is convinced that this blackout is a special operation to switch the ZNPP’s own needs to power from the Russian Federation. An information cover has been created specifically for this.

“By the end of 2025, the ZNPP management promised Kiriyenko to begin operating the ZNPP in accordance with Russian Federation standards. This does not mean connecting to the grid, but they need to show some success. The Russian Federation is extending its own power transmission line, elements of which were previously successfully damaged by Ukrainian means. Now it is at a high state of readiness, and to connect it, the electricity supply from Ukraine must be interrupted. Therefore, a ‘Ukrainian’ drone damaged phase C of the last live line at a distance of 2.8 km from the NPP. A relatively simple repair is needed, similar to what our repairmen did in literally hours. But they are not letting us near for repairs and are not repairing it themselves without explaining the reasons,” he writes.

According to him, the mode of operation on diesel generators can be continued indefinitely – as long as there is fuel. But the situation is being used to stir up fear. Allegedly, there is not enough diesel, and the generators could shut down at any moment. “The calculation is for a fool who wouldn’t think about what prevents them from refueling and repairing the line. Because of these fools, the international ‘community’ will put pressure on Ukraine to give up and allow the Russian Federation to ‘save the world from catastrophe’,” writes Shuster. “If we destroy the line they are building, a wave of hysteria will start – this is a special calculation. They will portray us as the creators of, if not a catastrophe, then an unacceptable risk. In this way, they are trying to tie our hands.”

The idea that the situation at the Zaporizhzhia Nuclear Power Plant is a Russian trap to connect the plant to the Russian grid is supported by Hryhorii Plachkov, former head of the State Nuclear Regulatory Inspectorate of Ukraine.

“In my opinion, this is a kind of trap. Now they will launch their power transmission line, we will strike it, and they will say that we are creating a catastrophe at the Zaporizhzhia Nuclear Power Plant. Therefore, what is happening now is a probing of the ground to reconnect the ZNPP to the Russian energy system or to the energy system operating in the occupied territories and in occupied Crimea to meet the plant’s needs,” he stated in a comment to Espreso.

Is a Chornobyl or Fukushima scenario possible?

According to Dmytro Humenyuk, head of the safety analysis department at the State Scientific and Technical Center for Nuclear and Radiation Safety, one generator is sufficient to power one power unit in a cold shutdown state. The ZNPP has three generators for each unit. If we assume that none of the generators work and the power unit is left without any power, then in a cold shutdown, the melting of nuclear fuel would begin in a few days (if the unit were operating at power, the fuel would start melting in about 3 hours). It would happen gradually, and some time would pass before the reactions that can no longer be stopped would begin.

At the same time, even if the Zaporizhzhia NPP were operational, an accident of the scale of Chornobyl is no longer possible because RBMK reactors are no longer used in Ukraine. The VVER reactors at the Zaporizhzhia plant have eliminated the shortcomings of the “Chornobyl reactors.” In particular, the possibility of an uncontrolled increase in power output in the reactor core, which led to the Chornobyl disaster, has been excluded.

As for the Fukushima accident in 2011, which is the second largest after Chornobyl, it was caused by an earthquake and a tsunami. The NPP was operating at power, the earthquake triggered the emergency protection, and the plant was supposed to switch to power from generators, but due to the powerful tsunami, the generators did not turn on.

“At Fukushima, the reactors were at power. At the Zaporizhzhia Nuclear Power Plant, the reactors are in a cold shutdown state. Therefore, a catastrophe of the scale of Fukushima or Chernobyl will not happen. But still, some local accident could occur if there is no external power and the diesel generators do not work,” says Hryhorii Plachkov. “However, the reactor core itself, the concrete confinement over the nuclear installation, and the fuel itself are designed to prevent catastrophic consequences, as many lessons have been learned since the accidents at Chornobyl and Fukushima. But causing trouble at the Zaporizhzhia Nuclear Power Plant is a piece of cake. You don’t have to think much to melt the reactor cores. This is also one of the occupier’s options – to melt the reactor cores so that when the ZNPP returns to Ukrainian control, they will either have to be repaired for a very long time or cannot be returned to commercial operation.”

After connecting the plant to its power lines, Russia may try to start a reactor

The danger could increase if the Russian Federation tries to bring one of the reactors out of cold shutdown. Greenpeace, which monitors the situation at the ZNPP via satellite images, believes that the Russian Federation may be preparing to start one of the reactors.

“In recent days, a series of parallel and significant events have taken place, which has led Greenpeace Ukraine to conclude that the Russian Federation and Rosatom may take advantage of the current crisis, which they deliberately created, to try to restore the connection to the temporarily occupied Russian energy system of Ukraine in the south and east of the ZNPP. The next step could be attempts to start at least one nuclear reactor,” the organization reports.

In a new study, Greenpeace points to several factors:

• Russia’s construction of a new 201 km power transmission line between substations in occupied Melitopol and Mariupol;
• Russia’s deliberate damage to the 750 kV power line near the ZNPP in the territory illegally occupied by Russia, a complete disconnection from the Ukrainian-controlled power grid, and the loss of power supply to the ZNPP;
• The completion of a new water supply system for the ZNPP cooling pond;
• The transition of plans to restart the reactor to the “final stage,” according to a statement by Russia’s state nuclear corporation Rosatom;
• The controversial role of IAEA Director General Grossi in supporting Rosatom’s nuclear business.

By the way, in early June, Rafael Grossi said that if enough water could be pumped from the Dnipro, all six of the plant’s reactors could eventually be restarted, although a “number of things” would need to be done first.

“Ukraine has stated that any attempt by Russian technicians to restart the plant would be dangerous as they are not certified to operate it. Grossi said that the Russian nuclear personnel are capable of carrying out a restart, and that the issue of certification is more political than technical,” Reuters reported at the time.

How the IAEA and the EU are reacting to the situation

“This is a threat to absolutely everyone. No terrorist in the world has ever allowed themselves to do with a nuclear power plant what Russia is doing now. And it is right that the world should not remain silent. I held a meeting with the military and the Ministry of Energy. I have instructed the government – the Ministry of Energy of Ukraine together with the Ministry of Foreign Affairs – to draw the world’s attention to this situation as much as possible,” said President of Ukraine Volodymyr Zelenskyy on September 30.

On the same day, the IAEA also issued a statement on the situation at the ZNPP. Although on September 25, when the largest NPP in Europe was already without external power and operating on generators, the head of the agency, Rafael Grossi, attended “Atomic Week” in the Russian Federation and shook hands with Vladimir Putin. The IAEA press release states that the agency is working with “both sides of the conflict.”

“Europe’s largest nuclear power plant has been without external power for over a week, the longest such event in more than three and a half years of war. I am in constant contact with both sides to ensure the plant is reconnected to the power grid quickly,” said Director General Grossi.

According to the IAEA, eight electric generators are currently operating at the ZNPP, nine additional units are on standby, and three are undergoing maintenance. Last week, the plant rotated the operation of those working to service some of the idle ones and ensure continuous availability. The plant has enough fuel for 10 days of operation. The water level in the cooling ponds is also sufficient.

“The ZNPP stated that it has the personnel and spare parts needed to repair the damaged 750 kV line, but has not yet been able to do so due to military activity in the area. For its part, Ukraine has stated its readiness to repair the backup 330 kV power line, which has been disconnected since early May, but the military situation has not yet allowed this either,” the press release says.

In contrast to the impartial statement of the IAEA, the EU in its statement called on Russia to immediately cease all military operations around the nuclear power plant to ensure the urgent restoration of power lines.

The nuclear power plant now depends solely on emergency diesel generators for the electricity needed to cool the six shutdown reactors and other essential nuclear safety functions. A prolonged loss of power could eventually jeopardize the safety systems.

“The EU fully supports the efforts of the IAEA to facilitate the repair of power lines in accordance with the seven indispensable pillars of nuclear safety and security outlined by the IAEA Director General. This includes adherence to pillar 4, which states that ‘there must be a secure off-site power supply from the grid for all nuclear sites.’ The seven indispensable pillars, as well as the five concrete principles for the protection of the ZNPP, must be fully respected. This is essential for further strengthening nuclear safety and security worldwide,” the EU statement reads. “Russia’s attempts to illegally seize ownership of the Ukrainian ZNPP have no basis under international law. Russia must immediately, unconditionally, and completely withdraw all its forces, military equipment, and other unauthorized personnel from the ZNPP and the entire territory of Ukraine. The return of the ZNPP to the full control of the competent and legitimate Ukrainian authorities is the only long-term solution to minimize the risk of a nuclear accident with global consequences.”

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