“The generators and the plant were never designed for this and have never operated in such a mode for so long,” he said.

The Russian-installed communications director for the power plant, Yevgenia Yashina, told the Russian news agency Tass that “the situation … remains under complete control”.

Kremlin spokesman Dmitry Peskov said on Wednesday that Russia was in constant contact with the IAEA about the plant. “The station and nearby facilities are subjected to constant attacks by the Kyiv regime. It would be, to say the least, absurd to accuse the Russian side of shelling a station that it itself controls. Despite this, Russian specialists and station personnel are doing everything possible to guarantee the station’s safety, which is reliably maintained.”

However, the head of Ukraine’s State Nuclear Regulatory Inspectorate, Oleh Korikov, maintained in a statement posted to Facebook that the current situation “poses great threats to nuclear and radiation security”.

“Ignoring the requirements and principles of nuclear and radiation, Russian shelling of power lines and the resulting damage, as well as obstructing Ukrainian specialists from restoring these lines,” Korikov said, “all of this could well lead to the worst-case scenario”.

Grossi said that his agency has been in “constant contact” with officials on both sides of the front lines. The generators are the “last line of defence”, he said, for the now-dormant plant, which has not generated power since Russia seized it in 2022 after invading the southern Ukrainian region of Zaporizhzhia, about 482km southwest from Chernobyl.

While not generating power, the facility requires electricity to cool its half-dozen reactors, averting massive disaster. Though the danger now is less than it would be if the plant – which once supplied 20% of Ukraine’s power needs, enough to export electricity to the rest of Europe – was running, Grossi warned that the nuclear fuel “could melt if power was not restored in time”.

Of the diesel generators, eight are in use, the plant’s Russian management reported to the IAEA. Workers are cycling those generators out with nine additional units – currently in standby mode – to keep them serviced. Another three generators are in maintenance. There are typically 10 days of diesel fuel on hand.

The plant reported it was possible to fix the 750-kilovolt electrical line that was damaged in September – but they have been unable to complete the work because of fighting in the area. Meanwhile, Ukraine has repeatedly offered to repair a backup 330-kilovolt power line that was disconnected in early May, though Russia has declined to take Kyiv up on this offer.

The plant caught the attention of Trump earlier this year, when he suggested that American ownership of the facility would help recoup investments from the Biden administration to defend Ukraine – and even keep the plant safe. Kyiv bristled at the proposition. Complicated by Russia’s occupation, the idea has since seen little momentum.

For now, Grossi said, “it is extremely important that off-site power is restored”.

Natalia Abbakumova in Riga, Latvia, contributed to this report.

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