Ukraine's Zaporizhzhya Nuclear Power Plant (ZNPP) lost the connection to its only remaining back-up power line today amid renewed indications of military activity in the area, in yet another incident highlighting persistent nuclear safety and security risks during the conflict, Director General Rafael Mariano Grossi of the International Atomic Energy Agency (IAEA) said today.
The IAEA experts stationed at the ZNPP reported that the sole remaining 330 kilovolt (kV) line was disconnected at 10:06am local time, leaving the plant entirely dependent on its sole remaining 750 kV line for off-site power. Before the conflict, the ZNPP had four 750 kV and six 330 kV power lines available.
The cause of the latest outage was not immediately clear, but it followed reports of military activity in the region and beyond. This was also confirmed by the IAEA team on the ground who heard numerous rounds of outgoing artillery fire this morning, as well as on Wednesday, when the firing of rockets was heard by the team.
"As has happened repeatedly during this devastating war, Europe's largest nuclear power plant has lost a key source of the electricity it needs to cool its reactors as well as for other essential nuclear safety and security functions. This morning's developments once again underline the very real dangers facing this major facility," Director General Grossi said.
Also before these latest events, the IAEA experts have continued to hear daily explosions over the past week, at various distances from the site.
Since August 2022, the ZNPP has suffered eight events with a complete loss of off-site power, most recently in December last year. The 330 kV line was also disconnected for three weeks earlier this year, but the main 750 kV line remained available at that time.
Separately today, Ukraine's national regulator, the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU), informed the IAEA that a research and development facility in the country's north-east - used before the war to produce radioisotopes for medical and industrial applications - had once again lost off-site power due to shelling. The facility now relies on emergency diesel generators, as it did during a previous week-long outage, from 22-29 March 2024. The on-site radiation situation is within the normal limits, SNRIU said.
The subcritical Neutron Source installation, located in the Kharkiv Institute of Physics and Technology (KIPT), was transferred to a deep sub-critical state at the start of the conflict, and its radioactive inventory is low. In November 2022, an IAEA safeguards and nuclear security expert mission found that the facility had been heavily damaged by shelling, but without any indication of radiological release or diversion of declared nuclear material.
"As this facility has been shut down since the start of the armed conflict more than two years ago, we do not currently expect the situation to have any consequences for public safety. But it also underlines the potential risks to nuclear safety and nuclear security during the military conflict and we will continue to monitor the situation at the facility," Director General Grossi said.
Earlier this week at the ZNPP, the IAEA team was informed that the plant was assessing the future operational status of its only heat-generating unit after the nearby town of Enerhodar - where most plant staff live - officially ended the winter heating season.
The ZNPP stopped producing electricity for the national grid in September 2022, but it has kept at least one of its six units in hot shutdown to provide district heating as well as process steam for liquid waste treatment at the site. After the plant earlier this year started operating four newly-installed diesel steam generators to handle such waste, reactor unit 4 has remained in hot shutdown primarily to help keep Enerhodar warm. The five other reactors are in cold shutdown.
This week, however, the IAEA experts stationed at the site were informed that on 1 April, Enerhodar decided to end its heating season for 2023-24 and shut down its own local heat generation, prompting the ZNPP to also re-consider the situation regarding unit 4.
"A decision to move unit 4 to cold shutdown would be more favourable for nuclear safety and security, but it should not detract from the fact that the situation at the Zaporizhzhya Nuclear Power Plant remains highly precarious, as this morning's power loss once again demonstrated," Director General Grossi said.
The IAEA team this week continued to conduct walkdowns at the site, including to some of the reactor units as well as the ZNPP inlet and discharge channels, where they also observed the cooling towers and their pumping station.
At the waterworks facilities, the team was informed that the ZNPP cooling pond currently receives approximately 400 m3/h of water from the sprinkler ponds as well as from the discharge channel of the nearby Zaporizhzhya Thermal Power Plant. The water supplied from the eleven underground wells is providing enough cooling water for the six units in shutdown, but still not enough to maintain the water inventory in the ZNPP cooling pond.
During a visit to the unit 4 reactor building the team observed the chemical analysis laboratory and the safety system rooms. No leaks or traces of boric acid were seen. But the experts noted what appeared to be some crystallised boric acid in one of the sump intakes during a visit to unit 1 sumps for the ECCS (Emergency Core Cooling System). Borated water is used in the primary coolant to help maintain nuclear safety functions. Although leaks may occur, prompt investigation, repair, and clean-up are crucial to prevent potential damage to any system important to nuclear safety.
During the walkdowns over the past week, the experts were not granted access to the cooling pond isolation gate, a location the IAEA last saw in November 2023, nor to the western part of the turbine hall of unit 6. As reported previously, the ZNPP has not provided timely and appropriate access for the IAEA experts to all areas that are important to nuclear safety and security.
The IAEA teams at the Khmelnytskyy, Rivne and South Ukraine NPPs as well as at the Chornobyl site reported that nuclear safety and security continues to be maintained, despite multiple air raid alarms over the past week. Maintenance in the unit 2 turbine hall at the Khmelnytskyy NPP has been completed and the reactor has returned to nominal power. Unit 4 at the Rivne NPP remains in planned outage. The IAEA experts at the South Ukraine and Rivne NPPs rotated during this past week.
