IAEA Director General Rafael Grossi after another complete shutdown of the Zaporizhia NPP from the power grid called for intensified efforts to restore the plant's backup power lines and confirmed the need for the IAEA team at the NPP to gain access to the nearby Zaporizhia Thermal Power Plant (ZTPP), also occupied by Russian troops.

"[Access] has yet to be granted despite assurances by Russian state nuclear company Rosatom. The ZTPP operates its 330 kV open switchyard, through which back-up power has in the past been provided to the ZNPP," according to Grossi's statement on the IAEA website.

The ZNPP's only remaining external 750 kilovolt (kV) power line was cut around 05:30 local time and re-connected after more than five hours, according to IAEA experts present at the plant. This morning's loss of all off-site power demonstrates the highly vulnerable nuclear safety and security situation at the Zaporizhia Nuclear Power Plant.

The IAEA recalled that ZNPP is today connected to the power system by a single 750 kV external power line, since on March 1, the last operating backup power line of 330 kV was damaged on the right bank of the Dnipro River, which has not yet been repaired.

"For more than two and a half months, this major nuclear power plant has only had one functioning external power line. This is an unprecedented and uniquely risky situation. Defence-in-depth – which is fundamental to nuclear safety – has been severely undermined at the ZNPP," Grossi said.

Initially after this off-site power cut, all the ZNPP's 20 diesel generators started operating, but 12 of them were later switched off. This left eight running, which is sufficient to operate all systems safely. The IAEA experts at the site were informed that there is enough diesel fuel for 23 days. After the 750 kV line was restored, the diesel generators were gradually turned off.

Five of the ZNPP's six reactors were already in a cold shutdown state before today's power outage, and preparations were under way to transfer also Unit 5 from hot to cold shutdown. Following the restoration of off-site power, Unit 5 is being returned to hot shutdown.

Elsewhere in the country today, a team of IAEA experts at the South Ukraine NPP said an emergency shutdown had occurred at one of its three reactor units. "Plant management informed the IAEA team that the automatic shutdown took place due to grid disturbance or instability. The SUNPP still has off-site power available," the report notes.