The International Atomic Energy Agency (IAEA) is assessing observations and information collected from its recent missions to Ukraine's electrical substations, conducted in the aftermath of attacks on the nation's energy infrastructure, as part of the Agency's ongoing commitment to monitoring nuclear safety and security, IAEA Director General Rafael Mariano Grossi said today.
Recent assaults on Ukraine's energy infrastructure, including a major attack on 25 December that caused some reactor units at the country's three operational plants to once again reduce their operating power for several hours, have reduced the stability of Ukraine's electrical grid. All affected reactor units subsequently returned to nominal full power.
During its eight-day mission from 16 - 23 December, IAEA experts gathered technical information about seven electrical substations critical to the safe operation of Ukraine's Khmelnytskyy, Rivne, and South Ukraine nuclear power plants (NPPs). A reliable and stable grid connection is essential to transfer the electricity generated by the operating NPPs and to receive off-site power, which is required for maintaining nuclear safety. The Zaporizhzhya NPP (ZNPP) and the Chornobyl site also depend on reliable and stable off-site power to maintain nuclear safety.
The IAEA team that visited the substations documented the damage and gathered critical evidence highlighting the electricity grid's vulnerabilities as a result of attacks on Ukraine's energy infrastructure. During the mission, the team met with experts from Ukraine's grid operator, nuclear plant operators, and nuclear regulator. Drawing on information from this mission and two previous substation assessments, the IAEA is working to identify and deliver targeted technical assistance to help prevent a nuclear accident.
"These attacks impact grid stability and jeopardise the reliability of the off-site power supply, creating risks to nuclear safety," said Director General Grossi. "Our ongoing missions to the substations and our presence at five nuclear power plant sites are essential for monitoring nuclear safety and security in Ukraine, particularly the reliable and stable provision of off-site power to the plants."
The IAEA Support and Assistance Mission to Zaporizhzhya (ISAMZ) has continued to carry out walkdowns and follow maintenance activities to monitor the status of nuclear safety and security systems and equipment at the plant.
In another instance highlighting the precarious external power situation, the IAEA team stationed at the ZNPP, were informed that the plant's last remaining 330 kV back-up power line was recently disconnected two times for maintenance from 20 - 22 December and from 24 - 25 December. Before the military conflict, Europe's largest NPP was connected to four 750 kV and six 330 kV off-site power lines.
The IAEA team was informed that unit 4's circulation pump used to maintain the movement and cleanliness of water in the ZNPP cooling pond was switched off on 18 December to maintain a level of water in the cooling pond. The ZNPP confirmed that water from the 11 groundwater wells is sufficiently feeding the sprinkler ponds which provide cooling to the six reactor units in their current cold shutdown states. The six reactor units at the ZNPP have not operated at power for more than two years.
The IAEA team was informed that planned maintenance activities were completed last week on safety trains in unit 2 and 6, as well as on one of the common emergency diesel generators. Additionally, diesel steam generators were operated between 12 - 30 December to treat roughly 800 cubic metres of liquid waste.
The team at the ZNPP continues to report hearing military activity in the vicinity of the plant. The ISAMZ team reported hearing explosions over the past days at various distances from Ukraine's largest NPP. No damage was reported to the ZNPP.
Separately, the IAEA teams at the Khmelnytskyy, Rivne and South Ukraine NPPs and the Chornobyl site also continue to report air raid alarms, and the Khmelnytskyy team were required to shelter several times in the past week.
Elsewhere in Ukraine, the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU) informed the IAEA that the subcritical neutron source facility at the Kharkiv Institute of Physics and Technology lost off-site power on the morning of 25 December, as a result of military activities. The facility, which remains shutdown, received power from its emergency diesel generator until off-site power was restored approximately five hours later.
