Ukraine’s Zaporizhzhya Nuclear Power Plant (ZNPP) lost again the connection to its last remaining operating 750 kilovolt (750 kV) power line this morning, but it is continuing to receive electricity from the grid through a back-up system, Director General Rafael Mariano Grossi of the International Atomic Energy Agency (IAEA) said.
The IAEA team of experts present at the ZNPP site were informed by senior operating staff that the 750 kV line was disconnected by sub-voltage protection – a system which automatically takes such action when the voltage drops too low – at around 4am local time.
Ukraine’s national nuclear operator Energoatom said that this was caused by shelling of a sub-station, which forms part of the grid’s electrical transmission system, located far from the plant itself.
It was the third time the ZNPP’s connection to this power line was lost over the past ten days, underlining the plant’s fragile power situation during the current military conflict in Ukraine.
The IAEA experts reported to Agency headquarters that the plant – which needs electricity for reactor cooling and other essential safety functions – now receives external electricity through the switchyard of the nearby thermal power station, a back-up arrangement that was restored last week.
For about ten minutes, one of the ZNPP’s 20 emergency diesel generators started operating after this morning’s loss of the 750 kV line, but it was soon switched off again as the back-up electricity system provided the necessary power.
Ukraine said that the shelling of the sub-station, which is also connected to the South Ukraine Nuclear Power Plant, did not impact the operating mode of that NPP.
At the ZNPP, the IAEA team reported that another three trucks with diesel fuel arrived today at the plant from Crimea, as well as a convoy with spare parts and consumables from the city of Zaporizhzhya. Yesterday, the IAEA team learned that a decision had been made not to continue start-up operations of reactor unit 5. However, the unit remains in a hot shutdown state in order to supply process steam to the ZNPP site.