The last remaining back up 330 kilovolt (kV) power line at the Zaporizhzhya Nuclear Power Plant (ZNPP), damaged since 1 March, remains disconnected and under repair, again highlighting the fragility of nuclear safety and security at Europe's largest nuclear power plant (NPP), Director General Rafael Mariano Grossi of the International Atomic Energy Agency (IAEA) said.
For three weeks, the ZNPP has received off-site electricity from only one remaining 750 kV main external power line. Though all six reactors at the ZNPP are in shutdown, with two in hot shutdown, the plant needs off-site power to perform essential nuclear safety and security functions. Without the back-up line, any damage to the 750 kV line will result in total loss of all off-site power to the plant.
On 9 March, the plant lost all off-site power for 11 hours when the 750 kV line was disconnected, forcing the plant to rely on its emergency diesels generators for reactor cooling and other essential nuclear safety and security functions.
Director General Grossi said that the situation at the plant remains perilous. The IAEA Support and Assistance Mission to Zaporizhzhya (ISAMZ) team currently present at the plant was informed that restoration of the line had been planned for 5, 10 and then 13 March but had not been possible. The latest reconnection date is scheduled for 23 March.
In an additional warning of the deteriorating situation, the ISAMZ team was informed that the connection to the 750 kV line may be disconnected for an unknown period of time to perform maintenance/repairs on the line. Currently, there is no information as to if or when this may occur or for how long. It is vital that there is the necessary coordination and communication between the Ukrainian electrical grid dispatcher and the plant.
"Nuclear safety at the ZNPP remains in a precarious state. If this disconnection from the main power line and repair work is performed while the 330 kV line is not available it will cause a complete loss of power and will make the plant reliant on diesel generators - its last line of defence - for the seventh time," said Director General Grossi. "I once again call for a commitment from all sides to secure nuclear safety and security protection at the plant."
The ZNPP, like all NPPs, maintains its preparedness for the loss of off-site power. On 20 March, the ISAMZ team reported that they observed the monthly test performed at Unit 4 for the loss of off-site power. The team reported that the emergency diesel generators successfully started, in line with nuclear safety requirements.
In addition, the Russian Federation has reported that Rosatom is working to restore three 330 kV lines at the thermal power plant switchyard into the grid system in currently Russian-controlled territory. The ISAMZ team has not been able to verify this information.
Separately, the ISAMZ team continues to meet with staff in the ZNPP training centre and in the reactor units. The team has observed personnel from NPPs in the Russian Federation receiving training in the reactor simulators and on-the-job training with experienced ZNPP staff in the main control rooms. ISAMZ was informed that the purpose of this training is to ensure that adequate staff are available to come and work at the plant in case of licensed staff shortages.
Since the start of the conflict, Director General Grossi has expressed serious concerns about the pressure that ZNPP staff are facing. "The reduced ZNPP staffing levels combined with psychological stress from the on-going military conflict is impacting the nuclear safety and security at the plant.
Also this week, teams of IAEA staff are travelling to Ukraine to complete the planned rotation of staff at the four other Ukrainian nuclear facilities, the Khmelnitsky, Rivne and South Ukraine NPPs, as well as the Chornobyl site.
