IAEA Observes Critical Generator Tests at Zaporizhzhya NPP Amid Power Risks

IAEA Observes Critical Diesel Generator Tests at Zaporizhzhya Nuclear Power Plant Amid Escalating Power Concerns and Ongoing Conflict in Ukraine.

The International Atomic Energy Agency (IAEA) has confirmed that emergency diesel generators (EDGs) at the Zaporizhzhya Nuclear Power Plant (ZNPP) are fully functional following a series of operational tests conducted this week. This development is crucial amid continued instability in off-site power connections at the plant, which lies on the frontline of the ongoing military conflict in Ukraine.

Director General Rafael Mariano Grossi emphasized the significance of these tests, stating, “As the off-site power situation at ZNPP is still highly precarious, it is very important that these diesel generators can immediately start up without any issues. Our experts were this week able to confirm that the diesel generators that were tested can fulfil their function if the plant once again were to lose its external connections. Continued vigilance in this respect is necessary.”

Emergency Preparedness Tested Under Strain

ZNPP, Europe’s largest nuclear power facility with six reactors, has faced repeated disconnections from Ukraine’s power grid throughout the conflict, forcing reliance on its backup power systems. These include 20 EDGs, which ensure continued cooling of the reactor cores and support other critical nuclear safety operations when grid power is lost.

In response to heightened safety concerns following the 2011 Fukushima disaster, Ukraine previously installed six mobile diesel generators (MDGs) – four connected to the reactor units and two stationed offsite. Last year, the plant acquired three additional MDGs, currently positioned next to turbine buildings but not yet connected to operational systems. The IAEA team observed testing of one EDG and one of these newly procured MDGs this week.

Fuel Supply and Safety Concerns

The IAEA also addressed reports circulating in local and international media of an alleged fuel spill from the diesel storage tanks at ZNPP. Upon inquiry, plant officials denied the claims, calling them “fake,” and asserted that fuel tanks remain intact with enough diesel stored to operate the generators for at least ten days without resupply. Nonetheless, the IAEA has formally requested direct access to the storage facilities for independent verification of fuel integrity and inventory.

Broader Monitoring and Maintenance Activities

Beyond generator testing, the IAEA team stationed at ZNPP has been actively inspecting various critical infrastructure and maintenance activities. This included an inspection walkdown of the site’s waterworks facilities and reactor unit 4, where the team discovered residual traces of dried boric acid and noted a defective pump seal—issues that could potentially impact safety systems if not addressed.

In a positive development, the IAEA confirmed that the 330 kilovolt (kV) switchyard of the nearby Zaporizhzhya Thermal Power Plant (ZTPP) was successfully reconnected to ZNPP’s 750 kV switchyard on Friday. This reconnection, made roughly six weeks after damage severed the link, now provides an alternative route for backup power to reach the nuclear plant—an essential redundancy given the unstable grid conditions.

Military Activity and Security Threats Continue

Military activity around the ZNPP remains an ever-present threat to nuclear safety. IAEA personnel reported hearing explosions and observing ongoing conflict at varying distances from the site throughout the past week. While no direct attacks on the facility were confirmed, the proximity of hostilities continues to heighten concerns.

Other Nuclear Sites in Ukraine Remain Under Close Surveillance

IAEA teams also continue their oversight missions at Ukraine’s other nuclear facilities: the Khmelnytskyy, Rivne, and South Ukraine Nuclear Power Plants (NPPs), as well as the decommissioned Chornobyl site.

• Khmelnytskyy NPP: A 750 kV transmission line was briefly disconnected at the request of the national grid operator on 21 March but was swiftly restored. Refuelling operations remain ongoing at one of the reactor units.

• Rivne NPP: One reactor unit is currently shut down for routine refuelling.

• South Ukraine NPP: A leaking pump was repaired, and reactor unit 1 has since resumed full operational capacity.

• Chornobyl Site: A fire incident temporarily knocked out a 330 kV line, but the line was reconnected following quick action by the Ukrainian State Emergency Service. The site also reported a near-incursion by an unmanned aerial vehicle (UAV) spotted just 3 kilometers away, followed by an explosion and further drone activity witnessed by IAEA personnel.

All IAEA teams stationed across these facilities have reported air raids over the past week, underlining the ever-present risks posed by the ongoing war and the fragile state of nuclear safety infrastructure in the region.

IAEA's Continued Mission

As part of its ongoing mandate, the IAEA remains committed to maintaining a constant presence at Ukraine’s nuclear facilities, aiming to prevent nuclear accidents, provide independent oversight, and offer technical support to Ukrainian authorities. Director General Grossi reiterated the importance of international cooperation in mitigating the risk of a nuclear disaster amid an active conflict zone.

“This situation remains deeply concerning. We are doing everything we can to support the safety and security of nuclear facilities in Ukraine, but we must remain alert and responsive to rapidly changing conditions on the ground,” Grossi said.

The IAEA has pledged to continue its round-the-clock monitoring, provide technical evaluations, and advocate for increased protections and access to critical infrastructure as the conflict continues into its third year.