Ukraine’s Zaporizhzhya Nuclear Power Plant (ZNPP) lost its immediate back-up 750 kV power supply to the reactor units for several hours during the week of 15 January. This was the latest incident underlining persistent nuclear safety and security risks at the site, director general Rafael Mariano Grossi of the International Atomic Energy Agency said on 19 January during its Update 207 report.
The failure on 18 January of two of the ZNPP’s back-up power electrical transformers showed the continuing vulnerability in the availability of external power, which the plant needs to cool its six reactors and for other essential nuclear safety and security functions.
Even though the back-up 330 kV line remained available, the failure reduced the redundancy of the already fragile power supply. The 750 kV and 330 kV lines are all that remain available for the NPP, compared to four 750 kV lines and six 330 kV lines before the conflict.
The back-up power supply was restored eight hours later when two other back-up power electrical transformers were put into operation. The ZNPP is investigating the cause of the failure, but state that there was no sign of external transformer damage. But failure of the 750 kV line has happened repeatedly during the armed conflict.
“The plant’s vulnerable power status remains one of the main dangers for nuclear safety and security at the site. The situation remains extremely worrying in this respect. The site has already lost all off-site power eight times since August 2022, forcing it to rely on emergency diesel generators,” said Mr Grossi.
During the past week, the IAEA experts discussed the plant’s maintenance activities with the ZNPP and were shown its high-level 2024 maintenance plan for such work, which is vital for nuclear safety and security. The ZNPP informed the IAEA team that the priority is to perform maintenance on the site’s safety systems as well as important activities not conducted last year. The annual maintenance plan includes the safety systems, diesel generators, unit transformers and the 750 kV electrical switchyard.
The IAEA team did not receive a copy of the plan, but based on discussions and information provided to the team the IAEA concluded that the ZNPP will not be implementing a comprehensive maintenance plan during 2024, although such a plan is considered essential to ensure plant safety and security. “This maintenance needs to be performed to ensure nuclear safety, especially in the current situation where the six reactors have been shut down for an extended period. It is important that the IAEA [is] able to fully assess nuclear safety at the ZNPP. We will continue to monitor the maintenance situation closely” said Mr Grossi.
The IAEA team has continued to conduct walkdowns at the site, including to all six main control rooms, although IAEA experts were not permitted to ask the staff questions about their qualifications and experience.
After being granted access to the reactor hall of unit 6 recently, the IAEA experts are still seeking access to the other reactor halls, as well as to parts of all six turbine halls that they have not yet been able to visit, as well as to some of the reactor rooftops. Such access is needed to monitor nuclear safety and security as well as adherence to the five concrete principles for the protection of the ZNPP, director general Grossi said.
Mines along the perimeter of the ZNPP between the facility’s internal and external fences, which were previously identified by the IAEA team and were removed in November 2023, are now back in place.
Elsewhere in Ukraine, the IAEA teams at the Rivne, Khmelnitsky, and South Ukraine NPPs as well as the Chornobyl site continue to report that nuclear safety and security is maintained despite multiple air raid alarms heard over the past week. The IAEA experts at the Khmelnitsky, Rivne and South Ukraine NPPs have reported air-raids on a near-daily basis with the teams at the Khmelnitsky and Rivne NPPs required to take shelter on several occasions.
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