Ukraine informed the International Atomic Energy Agency (IAEA) today that the country’s Zaporizhzhya Nuclear Power Plant (ZNPP) continued to have access to off-site electrical power for cooling and other safety functions and that one of its reactor units had been reconnected to the national grid, a day after the plant temporarily lost connection to a vital power line, Director General Rafael Mariano Grossi said.
The ZNPP’s connection to its last remaining operational 750 kilovolt (kV) line was restored yesterday afternoon after two power cuts and the disconnection from the grid of the plant’s two operating reactors, one of which was reconnected today, Ukraine said.
Director General Grossi said he welcomed the restoration of the external power line. But he added that the power cuts had highlighted the potential vulnerability of a major nuclear power plant (NPP) located in the middle of an active conflict zone and the critical importance of sending an IAEA expert mission to the six-reactor facility as soon as possible to help stabilise the nuclear safety and security situation there.
“I remain engaged in active and intense consultations with all parties to organize and lead an IAEA mission to the Zaporizhzhya NPP very soon, hopefully in the next few days. As yesterday’s sudden loss of the external power line showed, the IAEA’s presence at the site is urgently needed,” he said.
Ukraine told the IAEA that the ZNPP was now connected both to the 750 kV power line forming part of the national electricity grid and to a 330 kV line linking it to a nearby thermal power facility that can also provide off-site power if required.
During yesterday’s power cuts, emergency diesel generators were started in accordance with plant safety requirements in the event of such a power cut, but the 330 kV back-up line had remained connected and operational throughout that time, Ukraine said. The ZNPP normally has four external 750 kV power lines, but three of them were lost earlier during the conflict.
Power lines are primarily used to transport electricity from an operating nuclear facility through the grid in order to supply households, factories and others. NPPs also require a constant supply of electricity for their routine operations and to power the safety systems needed during an emergency or accident. If the external power line is lost, as was the case at the ZNPP yesterday, it is essential to have a back-up power source for the safety systems, in order to prevent any accident with radiological consequences for the public and the environment. The back-up power can be provided by the emergency diesel generators, or by additional reserve power lines.
A secure off-site power supply from the grid and back-up power supply systems are essential for ensuring nuclear safety. This requirement is among the seven indispensable nuclear safety and security pillars that the Director General outlined at the beginning of the conflict.