Energoatom, the Ukrainian state nuclear energy company, reported this Saturday a threat to radiation safety following a blackout on Friday at the Zaporizhzhia nuclear plant, under Russian control.

“Last night there was a complete blackout at the Zaporizhzhia NPP. On the afternoon of December 1, a breakdown occurred in the 330 kV power line between the Zaporizhzhia thermal power plant and Ferrosplavna, through which power is supplied to the plant from the Ukrainian electricity grid,” he said in a statement.

He added that at 02:31 last morning, during an air attack, the last 750 kV line between the Zaporizhia and Dniprovska power plants lost power and that due to the total blackout, the plant began to be supplied with diesel generators.

He stated that the 20 diesel generators were turned on automatically, of which 8 were subsequently left in operation.

“The biggest threat to security in this state is in unit 4. This is because the occupiers used it in violation of the terms of the Ukrainian regulator’s license to operate reactor units of nuclear power plants and kept it in a shutdown state hot,” he said.

He added that deactivating the main circulation pumps that cool the reactor core causes the plant to go into natural circulation mode.

“This mode is difficult for the reactor unit, its duration is limited by the design and can cause failures in the main equipment of the power unit. The unit requires an urgent transfer to a cold state,” he warned.

According to Energoatom, at 7:00 a.m. local time, Ukrainian specialists managed to reestablish the connection with the Ukrainian energy grid, that is, the 750 kV power line.

The Ukrainian regulator warned that “another blackout poses a threat to nuclear and radiological safety.”