Following discussions with the International Atomic Energy Agency, Ukraine’s Zaporizhzhya Nuclear Power Plant (ZNPP) has taken action to ensure an immediate supply of back-up electricity in case its main external power line is lost, as has happened repeatedly during the military conflict, IAEA Director General Rafael Mariano Grossi said today.
Frequent power cuts have remained a source of serious concern for safety and security at Europe’s largest nuclear power plant (NPP) as it needs electricity to cool its reactors and for other essential functions, even when all reactor units have been shut down. Since August 2022, the ZNPP has suffered eight events with a complete loss of off-site power.
When the ZNPP’s only remaining 750 kilovolt (kV) line is cut, the plant may still have access to off-site power through a 330 kV back-up line, if it remains connected to the grid. However, since mid-2023, this line has required manual intervention to become operational.
In discussions with the plant, the IAEA experts present at the ZNPP stressed that it was important for nuclear safety and security to address this matter. As a result, the plant carried out work on its back-up electrical transformers and two out of three are now operational, of which one is permanently connected to the on-site back-up power lines – known as busbars – of all six reactor units.
“This means that if the main power supply through the 750 kV switchyard is lost, the back-up line will automatically be able to provide electricity to the plant without manual, and hence delayed, intervention, provided it remains operational,” Director General Grossi said. “This is a significant development, as it enables independence and redundancy in the site’s power supply scheme, even though the overall off-site power situation at the Zaporizhzhya Nuclear Power Plant remains extremely fragile. This solution will only be effective if the 330 kV power line remains available, which – as we know from experience – is far from guaranteed.”
Underlining the continued dangers facing the plant, the IAEA team has in recent weeks continued to hear regular explosions some distance away from the site.
Five of the ZNPP’s six reactors remain in cold shutdown, while unit 4 is in hot shutdown to produce steam and heat, including for the nearby town of Enerhodar, where most plant staff live.
The IAEA team has continued to conduct walkdowns across the site as part of activities to monitor the nuclear safety and security situation at the ZNPP, as well as adherence to the five concrete principles for the protection of this major facility.
However, the IAEA experts remain unable to gain access to all parts of the site, and for the past two weeks they have not been allowed to access the reactor halls of units 1, 2 and 6. This is the first time that IAEA experts have not been granted access to a reactor hall of a unit that was in cold shutdown. This is where the reactor core and spent fuel are located. The team will continue to request this access.
In addition, access to some parts of the ZNPP’s turbine halls continues to be restricted, including those areas of reactor units 3, 4 and 6 over the past week. Also, the IAEA experts still await the access to the reactor rooftops planned on 19 December that didn’t happen due to stated security concerns.
In a separate development during a walkdown of the safety system rooms of unit 6 on 22 December, the IAEA experts observed boric acid deposits on valves, a pump and on the floors of several rooms in the containment building. The plant informed the team that the source of the leak is one of the boric acid storage tanks and that considering the small magnitude of the leak it is not planned to be repaired immediately, but rather as part of the planned maintenance of the impacted system. This type of leak can occur during the operation of a plant. However, this kind of event requires proper and timely attention, investigation and response from the operator, to prevent further and potentially more severe safety implications. The team will closely follow developments regarding this issue.
As reported earlier, the IAEA team continues to ask the plant for the maintenance schedule for 2024, which has not yet been provided.
The IAEA team has over the past two weeks continued to observe progress in the installation of four mobile diesel boilers at the site. As reported previously, the new units will generate additional steam needed for various nuclear safety functions at the site, including for waste treatment.
The site currently has nine mobile boilers, of which at least eight have been operating, providing additional heating during the winter.
The IAEA teams of experts at the Rivne, Khmelnitsky, South Ukraine NPPs and the Chornobyl site continue to report that nuclear safety and security is being maintained, despite wide-ranging missile attacks on Ukraine in the past week, which forced the IAEA experts at the Khmelnitsky NPP to take shelter three times.
The IAEA experts at the Rivne NPP were informed that a cruise missile flew close to the plant on 29 December, and their colleagues at the South Ukraine NPP were informed that missiles and drones crossed the region where the plant is located.