Zaporizhia NPP acts to ensure back-up electricity supply

9 January 2024

Following discussions with the International Atomic Energy Agency (IAEA), the Zaporizhia NPP (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.

Frequent power cuts have remained a source of serious concern for safety and security at the plant, which needs electricity to cool its reactors and for other essential functions, even when all reactor units are shut down. Currently five of 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 Energodar, where most plant staff live.

Since August 2022, ZNPP has suffered eight events with a complete loss of off-site power. When 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 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,” 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 ZNPP 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.”

Since Russia took control of ZNPP in March 2022 as part of its special military operation in Ukraine, the Russian national guard, Rosgvardiya, has been protecting the station. In October 2022, Russian President Vladimir Putin signed a decree formally transferring ZNPP to Russian jurisdiction under nuclear utility Rosenergoatom (part of Rosatom). A Russian Federal State Unitary Enterprise. Zaporizhia NPP was established by Rosenergoatom to operate the plant. However, Ukrainian nuclear utility Energoatom still claims ownership of the plant. IAEA has maintained a permanent presence at the plant since September 2022. Russia and Ukraine have blamed each other for shelling that has repeatedly downed power lines vital to cooling the reactors. Russia and Ukraine also accused each other of destroying the Nova Kakhovka dam, drastically reducing levels in the Kakhovka reservoir, which provides cooling water for the plant.

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. The IAEA team has continued to conduct walkdowns across the site as part of activities to monitor the nuclear safety and security situation at ZNPP, as well as adherence to the five concrete principles for the protection of this major facility, elucidated by Grossi in May 2023.

The five basic principles Grossi announced at the United Nations Security Council state that there should be no attack from or against the plant and that it should not be used as storage or a base for heavy weapons – multiple rocket launchers, artillery systems and munitions, and tanks.

Grossi noted that IAEA experts are currently 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&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. The team will continue to request this access.

In response to the IAEA statement, Renat Karchaa, adviser to the Director General of Russian nuclear utility Rosenergoatom, explained that IAEA staff had not been allowed to enter sealed units (GO - Germetichniye Obolochki) in ZNPP reactor compartments, which always remain sealed for safety reasons except in an emergency.

Sealing the GO in the reactor compartment restricts access to the main technological equipment, which is highly radioactive and ensures nuclear and radiation safety is maintained. In accordance with the technological regulations for the safe operation of power units, plant personnel are allowed to enter these sealed enclosures only in emergency cases or to perform routine maintenance. Currently, all six enclosures ZNPP are sealed.

Karchaa noted that IAEA experts are present on a regular basis when the GO and the reactor compartment building are sealed. He added that nuclear and radiation safety is the highest priority at ZNPP, and the plant's personnel work strictly in accordance with the regulations of the Russian Federation. "To date, after the IAEA experts carried out verification of nuclear materials in accordance with the requirements of regulatory documents, all six GOs at Zaporizhia NPP were sealed, he said. “In the sealed mode, personnel access to the GO is prohibited and is permitted only when there is an unambiguous justification and in emergency cases.”

Referring to the concern expressed by Grossi, Karchaa suggested that this may be due to insufficient knowledge or inadequate professional training of the IAEA employees. “A hermetic shell, and especially a sealed one, is not a museum or a zone for free walks”, he said. He added that he understands Grossi’s concerns but stressed that Russia takes a responsible approach to cooperation with the IAEA. “The content of the latest statement gives us reason to assume that either Rafael Grossi was not informed fully enough, or the information was submitted by people with low professional training, which is hard to believe,” Karchaa said.

In addition, IAEA said access to some parts of the ZNPP’s turbine halls continues to be restricted, including those areas of reactor units 3, 4&6 over the past week. IAEA experts are also awaiting access to the reactor rooftops planned on 19 December that did not take place because of 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. Grossi noted that 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. The IAEA team continues to ask the plant for the maintenance schedule for 2024.

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.

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