From the New York Times just now:
KYIV, Ukraine — Shelling once again threatened the safe operation of the Zaporizhzhia nuclear power plant, even as United Nations officials expressed cautious optimism that a permanent presence of its inspectors at the plant was helping to lower the risk of a nuclear disaster.
The plant lost the connection with its last remaining main external power line after shelling on Friday evening, forcing engineers to rely on a lower-voltage reserve line to power the cooling equipment needed to prevent meltdowns, the International Atomic Energy Agency said in statment.
Nuclear power plants must sometimes rely on external power drawn from the grid to cool the reactor cores and spent fuel. If the external power lines are cut, the Zaporizhzhia plant must turn to backup diesel generators, and if those malfunction or run out of fuel, a meltdown becomes possible.
https://www.nytimes.com/live/2022/09...ng-the-un-says