Ukrainian nuclear plant's longest power outage since war began 'critical' moment

Concerns are again mounting over the safety of Ukraine’s Zaporizhzhia nuclear power plant, which has been cut off from an external supply of electricity for more than a week.

Captured by Russian forces early in the war, the facility no longer supplies power to the grid but still needs electricity to cool its six inactive reactors and spent fuel. Emergency generators are currently keeping the systems running.

Rafael Grossi, head of the International Atomic Energy Agency, said conditions remain stable for now but warned that restoring reliable external power is vital. Ukrainian President Volodymyr Zelenskyy described the situation as “critical,” stressing that backup systems were never intended for prolonged use.

Here’s a look at what’s at stake — and what could happen if Zaporizhzhia suffers a total loss of power.

Longest outage since the war began

The Zaporizhzhia nuclear power plant, Europe’s largest, lost external power on September 23 and is now in its longest outage since Russia’s invasion in 2022. It is the latest in a series of incidents caused by fighting in the eastern region.

Grossi is holding talks with both Russian and Ukrainian officials in a bid to restore off-site power, underlining that the current backup system is “clearly not a sustainable situation in terms of nuclear safety.” Plant staff are rotating diesel generators to maintain a steady supply, the agency said. Eight units are currently operating, nine are on standby and three are under maintenance.

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Dmytro Gumeniuk, a senior official at Ukraine’s state nuclear safety agency, warned that Russian forces must ensure fuel deliveries to keep the generators running.

“The fact that it is running on diesel generators already represents a risk,” he told The Associated Press. “Even if they are refueled, this is still not a typical situation. Generators can fail, and they must be constantly monitored. We’ve never had a case like this before.” Although the equipment and staff are available to repair the main power line and a backup line, ongoing fighting has blocked access.

Fears of a total blackout The reactors at Zaporizhzhia have been shut down for more than three years, lowering the risk of a major incident. But a complete loss of power could lead to fuel overheating if cooling systems fail.

Ukrainians remain haunted by the Chernobyl disaster near Kyiv in 1986, when an explosion and fire released massive radiation with lasting impact.

The generators at Zaporizhzhia are considered a last line of defense. Fuel reserves are expected to last more than 10 days, though resupply continues.

With all reactors in so-called cold shutdown, fission reactions have stopped and temperatures and pressure are gradually declining – giving operators more time to respond before conditions become dangerous.

Cooling, however, remains essential, especially for spent fuel stored on-site, which must stay submerged to prevent overheating.

The IAEA says the plant is stable for now, but any disruption to backup systems could quickly escalate the risk.

Fighting continues near plant Russia declared Zaporizhzhia annexed in September 2022, along with Donetsk, Kherson and Luhansk, following disputed referendums held under military occupation.

The move was not internationally recognized, and fighting continues in all four regions, with Russia unable to gain full control despite advances in 2025.

Ukraine has blamed Russian artillery for the latest power loss at the Zaporizhzhia plant.

Moscow rejected the accusation, with Kremlin spokesman Dmitry Peskov calling it “stupid” to suggest Russia shelled a facility it controls.