Ukraine’s Nuclear Safety on Edge as Zaporizhzhya Plant Loses Final Backup Line

The IAEA's on-site team at ZNPP continues its monitoring efforts amid sporadic explosions heard from a distance throughout the past week.

The International Atomic Energy Agency (IAEA) has raised fresh concerns over the ongoing vulnerability of Ukraine’s nuclear infrastructure after the Zaporizhzhya Nuclear Power Plant (ZNPP) lost connection to its only remaining backup power line. The disconnection of the 330-kilovolt (kV) line occurred just before noon local time on Wednesday, a consequence of heightened military activity in the area, as confirmed by Ukraine’s Ministry of Energy.

This latest setback has left the ZNPP entirely reliant on its single remaining 750 kV power line to provide the electricity necessary for critical functions such as cooling nuclear fuel and maintaining reactor safety systems. Any further damage or disruption to this last line could leave the plant without external power – a scenario that has already happened eight times since the conflict began.

Director General of the IAEA, Rafael Mariano Grossi, emphasized the precarious state of the plant's power supply. “A secure supply of off-site power from the grid for all nuclear sites is one of the seven indispensable pillars of nuclear safety and security that we outlined early in the war. It is obvious that this supply is far from being secure,” he said. Grossi added that the situation remains "a deep source of concern" not just for the ZNPP, but for the broader stability of Ukraine’s nuclear facilities.

IAEA Continues On-Site Monitoring Despite Risks

The IAEA's on-site team at ZNPP continues its monitoring efforts amid sporadic explosions heard from a distance throughout the past week. Their recent activities included a comprehensive site walkdown, checking water levels in sprinkler ponds, testing an emergency diesel generator, and inspecting electrical breakers and instrumentation of units 3 and 4.

Meanwhile, logistical challenges have delayed the scheduled rotation of IAEA staff at the plant. The current mission, labeled ISAMZ27, has been stationed at ZNPP for over two months – longer than usual due to the escalating risks on the front lines. Grossi said he remains in daily communication with both Ukraine and Russia to secure a safe rotation for the team, reiterating that his primary focus is the safety of IAEA personnel and the plant itself.

Drone Attack Causes Serious Damage at Chornobyl Site

In another troubling development, the Chornobyl nuclear site is recovering from significant damage caused by a drone attack in mid-February. The strike resulted in fires that took several weeks to extinguish, damaging the New Safe Confinement (NSC) arch structure built over the destroyed reactor.

Preliminary assessments show that the outer cladding of the NSC suffered around 330 penetrations, each 30–50 cm wide. The stainless-steel panels, insulation layers, and crucial membrane structures have all been compromised. Furthermore, the NSC’s main crane system, including its maintenance garage and several control cabinets, was disabled by both the impact and the firefighting efforts.

Despite the damage, critical safety systems such as radiation and seismic monitoring, decontamination units, and fire protection measures remain operational. However, ventilation systems, although still functional, have not been reactivated since the incident.

Grossi noted, “We are gradually getting a more complete picture of the severe damage caused by the drone strike. It will take both considerable time and money to repair all of it.” Importantly, radiation levels at the Chornobyl site remain unchanged, indicating no release of radioactive material occurred.

Current Status of Other Ukrainian Nuclear Plants At Ukraine’s three operational nuclear power plants – Khmelnytskyy, Rivne, and South Ukraine – five of nine reactor units are currently online and supplying power. The remaining four are offline for routine maintenance and refueling, with two units expected to resume operations shortly.

IAEA teams stationed at these plants continue to report frequent air raid alarms. On April 30, staff at Khmelnytskyy NPP were forced to shelter in place due to incoming threats.

IAEA's Continued Support and International Contributions

Despite challenges, the IAEA remains committed to supporting Ukraine’s nuclear safety infrastructure. Recent deliveries as part of the agency’s assistance program include radio-communication systems for Khmelnytskyy NPP and the Centralized Spent Fuel Storage Facility, funded by the European Union. Additionally, the Ukrainian state enterprise USIE Izotop received dose assessment software with funding from New Zealand. Since the war began, the IAEA has delivered a total of 135 consignments of aid and equipment to bolster nuclear safety and security in Ukraine.

As the war in Ukraine grinds on, the country’s nuclear facilities continue to operate under the constant threat of power disruptions, military damage, and logistical challenges. The IAEA’s presence and international support have proven vital, but the latest developments at both Zaporizhzhya and Chornobyl underscore the urgent need for sustained attention, resources, and diplomacy to avoid a catastrophic nuclear incident.