The Ukrainian Zaporizhia Nuclear Power Plant (ZNPP) has once again lost access to external electricity and is instead relying on its emergency diesel generators for the power it needs for reactor cooling and other essential nuclear safety and security functions, Director General Rafael Mariano Grossi of the International Atomic Energy Agency (IAEA) said today, using information provided by the IAEA staff on the site.

The IAEA team at Zaporizhia NPP also said that the two reactors, which were in hot shutdown mode to provide the power plant and the nearby city of Energodar with steam and heat, will be prepared for cooldown. Four others remain in cold shutdown.

The IAEA also said the national operator of Ukraine, Energoatom, reported that "due to a decrease in the frequency in the power system of Ukraine at the Rivne, South Ukraine and Khmelnytsky nuclear power plants, emergency protection worked, as a result of which all power units were automatically disconnected. Currently, they work in the design mode, without generation into the power system."

As Grossi noted, the latest incident at the ZNPP highlights the increasingly dangerous and difficult situation with nuclear safety and security at Europe's largest nuclear power plant.

He said the ZNPP has been disconnected from the national grid several times during the current military conflict in Ukraine, most recently in early November when it took two days to restore external power supplies.

The team of IAEA experts present at Zaporizhia NPP said it lost off-site power at 15.30 local time today "when it was fully disconnected from the grid, following reports of widespread military action targeting Ukraine’s energy infrastructure."

Initially all the site's 20 diesel generators started operating automatically, and now eight of them are supplying the site with back-up electricity needed for all safety related equipment. The other 12 diesel generators are in stand-by mode.

The IAEA recalls that reactors need power for cooling and other essential nuclear safety and security functions also when they are in shutdown mode and do not produce electricity anymore. In the case of an external power loss, they have emergency diesel generators that can provide back-up electricity for a limited period of time, at least for 10 days in the case of the ZNPP.