The Zaporizhzhia Nuclear Power Plant (ZNPP), the largest nuclear plant in Ukraine and Europe, has now been in a blackout for nearly three consecutive weeks. All that time the plant has been operating on emergency diesel generators, which supply power to cool the reactors and ensure safety.
After the Fukushima disaster in 2011, European regulators set a rule that a nuclear power plant can operate without external power for no more than 72 hours. Exceeding this limit increases the risk of a nuclear catastrophe. But as usual the Russians are disregarding such regulations, as they do with most international laws and the rules of war.
Why have the occupiers once again cut off power to the ZNPP, and what might happen next? Ukraine's Foreign Minister Andrii Sybiha believes this is a "test" blackout – part of preparations to integrate the plant into the Russian grid. "The next step is even more dangerous: starting up a reactor under occupation – without proper cooling, without any licence, and beyond any control," Sybiha warned.
Is this a realistic scenario? What are the risks for Ukraine and the world, and how can it be stopped?
How Russia occupied the ZNPP
Early March 2022. Enerhodar, the ZNPP's satellite city, was under attack, fires raged nearby, and Russian tanks were firing at the nuclear facility. At that moment, the world was on the brink of another Chornobyl.
There were hopes that the International Atomic Energy Agency (IAEA) would intervene and quickly end the occupation. But the Russians brought military equipment and weapons onto the premises of the plant, mined the surrounding area, and restricted staff access.
Since then, the plant has endured constant disruptions in communications and the electricity supply from the Ukrainian grid. Russian attacks on power transmission lines have repeatedly left the ZNPP without power, forcing its reactors into a cold shutdown state (when no nuclear reactions occur) and halting electricity generation.
During this period, staff worked at gunpoint and control over the facility was gradually seized by Rosatom, Russia's state-run nuclear power operator. The Kremlin has made no secret of its plans to connect the ZNPP to its own power system, but various technical, organisational and safety issues have prevented it from doing so. Nevertheless, systematic efforts in this direction have continued.
Preparing for a restart: what the Russians have done
Since 2023, the Russians have been laying the groundwork to restart the illegally occupied plant, working in at least two areas – information and technical.
In the information sphere, they are trying to create the illusion that there is "order at the plant": spreading claims about the supposed "technical readiness of the units", "scheduled maintenance", or "routine system checks". In reality, this is a façade aimed at convincing the world that the ZNPP can safely operate under Russian control.
In the meantime, technical preparations are also underway. The Russians are developing infrastructure to try to integrate the nuclear power plant into their grid. According to satellite intelligence analysed by Greenpeace, the Russians have focused on several key projects over the past two years.
The first is the construction of a 201-km power transmission line between substations in the occupied cities of Melitopol and Mariupol. This line is part of the Russian Federation's plan to connect the energy systems of the temporarily occupied territories to its own grid.
The second is the construction of a water supply system to cool the reactors – a particularly urgent issue since the destruction of the Kakhovka hydroelectric power plant.
In addition, the Russians have deliberately damaged the 750-kV power lines near the plant. This caused the tenth blackout at the ZNPP, forcing it to switch to backup diesel power. According to Greenpeace Ukraine, these actions indicate that Russia may attempt to connect the occupied plant to the Russian grid. Their next step could be to restart one of the reactors.
Is it possible to restart reactors under occupation?
The experts and officials Ekonomichna Pravda spoke to emphasised that restarting even one reactor would be a complex, dangerous and expensive process – but it is technically possible.
"There are no technical problems that cannot be solved, so in theory it is possible," said a representative of one Ukrainian energy company. "The real issue is the safety factors, which remain critical and are not going to go away until the hostilities end."
According to Sean Burnie, a nuclear specialist at Greenpeace Ukraine, from a technical standpoint Rosatom can only start up one reactor at the moment.
"Although we do not know the details of these plans, our analysis of documents, Russian statements and satellite images shows a clear trajectory towards start-up. Our assessment is based on the fact that, given the available cooling water, operating one reactor at reduced capacity in generation mode is possible," said Burnie.
He noted that to operate several reactors Rosatom would have to ensure a much larger volume of water in the cooling pond at the ZNPP, which is not currently possible.
A senior Ukrainian official believes that the Russians are unlikely to be able to restart or operate even a single reactor until a ceasefire is in place: "They will continue to carry out provocations to achieve certain political or military goals, but the start-up and operation of a reactor during wartime are unlikely." Burnie agrees: "Russia's covert aim is to use the threat of restarting the plant as a tactical and strategic weapon to achieve military objectives."
Could a Chornobyl- or Fukushima-style disaster occur?
From a technical standpoint, the situation at the plant is critical. This has been stated by President Volodymyr Zelenskyy, representatives of Ukraine's Energy Ministry, Energoatom and the IAEA, and nuclear energy experts. Ukrainian experts are under no illusions: starting up even a single reactor in the current conditions would be a crime that would cost the world dearly.
This is confirmed by radiation and nuclear energy expert Jan Vande Putte: "There are risks resulting from Russia's actions. Their scale is broad and depends on the type of incident, and above all on what measures the Russian occupiers take or do not take."
The ZNPP has 12 sources of radioactive material: six nuclear reactors and six spent fuel pools. All of them could lead to radioactive substances being released into the environment.
"If there is a complete loss of power at the plant, including generators and batteries, and if the reactors are in a shutdown state, then the decisive factor will be Russia's actions and whether the automatic safety systems operate as designed. Depending on these factors, the critical element will be the amount of time until the nuclear fuel is damaged and radioactive emissions begin," Vande Putte explained.
Greenpeace estimates that at least two weeks would pass at the ZNPP before the nuclear fuel heats up to the point of damage. It could even take more than a month, depending on which of the twelve sources is involved and what actions the Russians take. Were Russia to start up one or more reactors, the consequences would become even more dangerous.
"If any reactor begins producing electricity again, the scenarios start with the fact that in the event of a power outage, including the loss of emergency generators, the nuclear fuel would quickly overheat. Under such circumstances, the nuclear fuel would be damaged and a meltdown would occur within a few hours," Vande Putte concluded.
Can the world end the occupation of the ZNPP?
The international community has sufficient leverage to influence Russia regarding the de-occupation of the plant. The key is to ramp up sanctions pressure on Rosatom and its subsidiaries to remove Russia from the global nuclear framework.
Despite the war, the Russian nuclear corporation continues to operate on global markets, including in the European Union, Türkiye, India and Egypt. Restricting contracts, halting joint projects and freezing assets would send a strong signal to the Kremlin.
IAEA member states should be playing a key role in containing the Russian threat looming over the ZNPP. Their support and political pressure should be continuously drawing the world's attention to the nuclear risks created by the occupation of the plant. Yet IAEA Director General Rafael Grossi has been sending out contradictory and troubling signals regarding the organisation's stance towards Russia and its nuclear sector.
It was telling that the day after the tenth blackout at the ZNPP, from which the plant has not yet recovered, Grossi was in Moscow as a guest of honour at Atomic Week, a conference organised by Rosatom.
In a speech, Grossi thanked the Russian nuclear industry, calling it a "reliable partner", and emphasised his friendly relations with Rosatom Director Alexei Likhachov. Such a gesture appears to turn a blind eye to Russian aggression and raises legitimate questions about whether the IAEA can be considered an impartial arbiter.
Author: Mykola Topalov
Translation: Myroslava Zavadska and Anastasiia Yankina
Editing: Teresa Pearce