A fire at a cooling tower of the Russian-controlled Zaporizhzhia nuclear power plant (Image: UKRAINIAN PRESIDENTIAL PRESS SER)
Ukraine’s Zaporizhzhia nuclear plant faces meltdown risks from its longest blackout since Russia’s 2022 invasion, with one expert warning of a single power line’s deadly vulnerability. The plant lost its last connection to the external grid on September 23, marking the 10th such outage since the war began, according to the International Atomic Energy Agency (IAEA).
As of Friday, ZNPP remained in a cold shutdown with all six reactors inactive, but it requires continuous electricity to power cooling systems for spent nuclear fuel. IAEA Director General Rafael Grossi described the situation as “clearly not sustainable in terms of nuclear safety” during talks with Russian and Ukrainian officials this week. Nickolas Roth of the Nuclear Threat Initiative think tank emphasised the fragility of the plant’s power infrastructure.
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Russian President Vladimir Putin (Image: Getty)
He told Express.co.uk: “For much of this year, the site has relied on a single functioning transmission line instead of multiple redundant connections.
“That creates a single point of failure: if that one line goes down, the plant loses the electricity needed to keep cooling and safety systems operating.”
The outage has been attributed to fighting near the plant, with Ukraine accusing Russian forces of shelling the last remaining 750 kV power line.
A Greenpeace satellite investigation released on Wednesday found no major damage to the line, fuelling speculation of sabotage.
Moscow denied the claims, with Kremlin spokesman Dmitry Peskov calling them “stupid” and asserting that Russia would not target a facility under its control.
ZNPP, Europe’s largest nuclear power plant, was captured by Russian forces in March 2022 and formally annexed by Moscow following disputed referendums later that year.
Ukrainian President Volodymyr Zelensky (Image: Getty)
The facility no longer generates electricity for the grid but houses thousands of tons of spent fuel that must remain submerged in water to prevent overheating. Ukrainian officials, including President Volodymyr Zelensky, have labelled the blackout “critical,” noting that backup generators were “never intended for prolonged use.”
Mr Roth outlined specific risks in the event of a total power loss. Referencing the need for contingency plans to mitigate such scenarios, he said: “A complete loss of power could lead to fuel overheating if cooling systems fail.”
He also called for governments to “develop plans to ensure the continuity of nuclear security operations during major crises,” including regular exercises simulating extended external threats.
Among the recommended measures are protecting supply chains for diesel fuel, transferring spent fuel to dry casks when possible, and securing off-site power sources.
Ukrainian nuclear safety official Dmytro Gumeniuk echoed these concerns, saying: “The fact that it is running on diesel generators already represents a risk. Even if they are refuelled, this is still not a typical situation. Generators can fail, and they must be constantly monitored.”
Current fuel reserves are expected to last more than 10 days, with plant staff rotating eight operational generators while nine remain on standby and three undergo maintenance.
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However, access to repair the damaged line has been blocked by active combat in the region, where Russian advances in 2025 have yet to consolidate full control.
Under Russian occupation, IAEA access to ZNPP has been limited, complicating oversight. Roth stressed the need for adherence to the IAEA’s five principles on nuclear safety, which include prohibiting attacks on the plant or its infrastructure and ensuring off-site power availability.
Mr Roth said: “Both Russia and Ukraine should affirm their commitment.
“The plant should not be used to store or base heavy weapons or military personnel that could be employed for attacks. Off-site power must not be put at risk, and every effort should be made to ensure its availability and security at all times.”
Highlighting the human element, he said: “First and foremost, Ukrainian reactor operators must be able to manage the plant without fearing for their lives and the lives of their families. They need safe working conditions and clear lines of communication with their national regulator.”
The European Union expressed concern in a statement from the European External Action Service on Oct. 2, urging both sides to prioritise de-escalation around nuclear sites.
The statement read: “Last week, the Zaporizhzhia Nuclear Power Plant has again lost connection to its last external power supply,” calling for immediate restoration.
Russian officials at the plant announced on Thursday that two additional backup generators would be activated to bolster supplies. Despite these steps, Mr Grossi warned that prolonged reliance on diesels heightens the risk of mechanical failure, potentially escalating to a radiological release similar to the 2011 Fukushima disaster in Japan.
The situation evokes memories of the 1986 Chernobyl meltdown, which released massive radiation across Ukraine and Europe. While ZNPP’s cold shutdown reduces immediate meltdown risks compared to Chernobyl’s operating reactors, experts such as Mr Roth warn that complacency could prove fatal.
He said: “Through close coordination, governments, nuclear facilities, and regulators should conduct regular exercises… including those that go beyond the design-basis threat.”
As diplomacy continues, the IAEA reports the plant remains stable for now. But with fighting persisting near the facility, the margin for error is razor-thin.