The Zaporizhzhia Nuclear Power Plant is the largest in Europe — six reactors on the bank of the Kakhovka reservoir in southern Ukraine — and it has sat inside the war since Russian forces seized it in the first weeks of the 2022 invasion. All six reactors are shut down, but a shut-down reactor is not a safe one: its fuel and the used fuel stored beside it keep generating heat for years and must be actively cooled, which takes electricity and water without interruption. The question that matters is not who is winning the war around the plant, but whether the plant stays cool, on whose observation, and who answers for it when it does not. As of early September 2026 it has been running on emergency diesel for more than two weeks, with no connection to the grid at all and a fuel margin now measured in days.

The vulnerability is off-site power. Cooling pumps run on external electricity; before the war the plant drew it from ten separate lines. Four years of fighting cut those to one, and on 20 August 2026 the last of them — the 330-kilovolt Ferosplavna-1 line — went down after military activity north of the Dnipro, leaving the site with no grid connection at all. From that moment the reactors and their spent-fuel pools have been cooled only by the plant's roughly twenty diesel generators. If those run out of fuel before power is restored, the result is a 'station blackout': cooling stops, and given enough time the water in the pools boils off and the fuel overheats. The generators are only as safe as their fuel supply, and that supply is the real weakness — the off-site fuel farm has not been resupplied since March, a May delivery was blocked by fighting, and the IAEA's inspectors have not been allowed to see the storage since March 2025. When the fuel runs short the plant's only levers are to run fewer generators and to cool intermittently, both of which trade safety margin for time. The agency has negotiated a series of localized ceasefires to get lines repaired — seven during the war so far, the most recent of them to let Ukrainian technicians reach Ferosplavna-1.

Around the cooling problem sits an accountability vacuum. Drones and shelling repeatedly strike the site or its surroundings — in late August three drones hit the cooling pond, the dry spent-fuel store and the sprinkler system within two days, injuring two workers — yet through the entire occupation no determination of who fired has ever been published. Each side blames the other, and each has a reason to: Energoatom, the plant's lawful pre-occupation operator, and Rosatom, the Russian corporation now running it, are both interested parties, authoritative about their own actions and unreliable about the other's. The one independent witness is the IAEA, whose team has been stationed inside the fence since 2022 and whose numbered Director General updates carefully separate what the inspectors saw for themselves from what the plant told them — a distinction that runs through every figure about the plant, including the fuel-margin numbers, which are the operator's reports rather than the inspectors' measurements. The instruments meant to hold someone responsible — the seven pillars of nuclear safety, the five principles the agency set for Zaporizhzhia, the resolutions of its Board of Governors — describe what should not be done to a plant in wartime but cannot compel it.

So the story stands at a familiar, dangerous equilibrium: a plant that is never quite safe and never quite in catastrophe, kept on the near side of disaster by generators, occasional trucked-in diesel, and ceasefires brokered line by line. What is unresolved is everything that matters — whether off-site power is restored before the fuel runs low, whether the ceasefire zones the agency brokers hold long enough for repairs to finish, and, underneath both, whether anyone will ever be named as accountable for firing on a nuclear plant. Russia's operator publicly disputes the agency's account of how close the plant is to the edge; that dispute is unresolved, because no independent party can yet settle it.