By Francois Murphy
VIENNA (Reuters) -Shelling on Tuesday damaged a backup power line at the Russian-held Zaporizhzhia nuclear power plant (ZNPP) in Ukraine, which has already lost all four of its regular power lines, the U.N. nuclear watchdog said in a statement on Wednesday.
The International Atomic Energy Agency (IAEA) said there was no immediate impact from the damage to one of its three backup power lines because the plant was already disconnected from the grid.
Like all nuclear power plants, Zaporizhzhia needs power to keep cooling the nuclear fuel in its reactors and its spent fuel. Its one operating reactor is supplying power but with each external power line that goes down, it loses a line of defence against potential nuclear meltdown.
"Of the three backup lines between the ZNPP and the thermal power station, one is now damaged by shelling, while the two others are disconnected, senior Ukrainian operating staff informed IAEA experts present at the plant since last week," the IAEA statement said, referring to a nearby coal-fired plant.
Russia and Ukraine have blamed each other for shelling that has occurred close to the plant and within its perimeter, risking nuclear catastrophe. Russian forces took over the plant soon after their Feb. 24 invasion of Ukraine but Ukrainian technicians still operate the power station.
Another of the backup lines was disconnected earlier this week to extinguish a fire.
Zaporizhzhia in southern Ukraine has six reactors and is Europe's biggest nuclear power plant.
Ukraine said on Wednesday it might have to shut down the plant to avoid a disaster and called on residents in areas nearby to evacuate for their own safety.
"While the plant also has emergency diesel generators available if needed, (IAEA) Director General Grossi has repeatedly expressed concern about the power supply situation," the agency said.
(Reporting by Francois Murphy; Editing by Chris Reese and Grant McCool)