The Organisation for Economic Co-operation and Development (OECD) and its Nuclear Energy Agency (NEA) have kept a close eye on Ukraine’s nuclear safety for more than four years of war. By partnering with the United Kingdom, the NEA launched a Visiting Experts Programme that brings Ukrainian specialists to the Agency, even as local conditions make data collection difficult. The agency repeatedly stresses that the information it gathers comes from “verifiable and reliable sources” because the on-ground situation remains highly volatile.
One of the first milestones of the conflict-era transformation was the successful synchronisation of Ukraine’s and Moldova’s electricity grids with the Continental European Grid on 16 March 2022. That alignment was intended to stabilise power supplies for all civil and industrial consumers, including the nation’s nuclear facilities.
Zaporizhzhia Nuclear Power Plant – a case study of chronic power loss
Ukraine operates fifteen pressurised-water reactors of the Russian-designed VVER type, managed by the State Enterprise National Nuclear Energy Generating Company “Energoatom”. Four sites host these reactors, with the Zaporizhzhia Nuclear Power Plant (ZNPP) housing the largest fleet – six reactors. The plant is overseen by the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU) and relies on a complex network of high-voltage lines for off-site power the external electricity essential for reactor cooling and safety systems.
Since the invasion, ZNPP has suffered a series of complete off-site power outages, each triggering its emergency diesel generators (EDGs). The pattern is stark: from the 11th loss in December 2025 to the 25th loss by August 2026, the plant has been forced to start diesel generators automatically or manually, sometimes with only a fraction of its twenty EDGs coming online because of fuel shortages and maintenance constraints. By late September 2026 a revised emergency plan stipulated that only four of the twenty generators would start automatically, with the rest requiring manual activation – a direct response to dwindling diesel reserves.
Key incidents include the disconnection of the sole 330 kV Ferosplavna-1 line on 20 August 2026 following combat on the Dnipro River, the longest outage since a September-October 2025 event, and a brief restoration on 7 September 2026 after technicians repaired the line. Diesel fuel stocks have hovered at the minimum regulatory ten-day supply, with the most recent delivery in March 2026 and a delayed May shipment due to military activity. The plant also relies on diesel-fired boilers for winter heating and waste-water processing, making fuel logistics a critical vulnerability.
Other Ukrainian nuclear sites – drone activity and power constraints
Beyond Zaporizhzhia, the country’s other reactors face a similar mix of operational strain and hostile surveillance. The Khmelnytskyi Nuclear Power Plant (KhNPP) operating two reactors and constructing two more, has logged numerous drone and missile sightings throughout 2025-2026, with spikes of up to fifteen flights in a single day. Similar patterns emerged at the Rivne Nuclear Power Plant (RNPP) and the South Ukraine Nuclear Power Plant (SUNPP) each reporting dozens of unmanned-aerial-vehicle (UAV) incursions and occasional missile alarms between 2024 and 2026. These incursions have prompted temporary power reductions, especially when attacks have targeted nearby substations or transmission lines.
Both RNPP and SUNPP have repeatedly lost access to one of their high-voltage off-site lines, forcing reliance on a single backup line and, in some cases, on emergency diesel generators. For example, RNPP’s 750 kV line was cut in December 2025, and SUNPP lost a 750 kV line in October 2025, each event accompanied by heightened IAEA monitoring and local air-raid alerts. Despite these setbacks, the plants have managed to keep all reactors in cold or hot shutdown modes, using groundwater wells and auxiliary cooling ponds to sustain the necessary water flow for residual heat removal.
In the exclusion zone of the historic Chornobyl Nuclear Power Plant (ChNPP) the situation is compounded by the presence of the New Safe Confinement (NSC). The NSC suffered a damaging drone strike in February 2025, igniting fires that compromised its multilayer insulation and sealing membranes. Subsequent assessments confirmed that radiation levels remained within safe limits, but the incident underscored the vulnerability of even decommissioned facilities. Throughout 2025-2026, the zone has seen a steady stream of UAV flights, sometimes exceeding one hundred in a 24-hour window, prompting the IAEA to label the airspace as a “high-risk monitoring zone”.
International monitoring and support
The International Atomic Energy Agency (IAEA) maintains a continuous presence at all Ukrainian nuclear sites, documenting explosions, artillery fire, and drone activity. Observers have confirmed that, despite frequent interruptions, the core safety systems—particularly the EDGs—have remained functional. The agency also assists with technical supplies, such as spare parts for diesel generators at SUNPP and fuel assemblies for Westinghouse-type reactors being introduced at KhNPP.
Continuous verification, fuel logistics, and the resilience of backup power infrastructure remain the linchpins of the country’s nuclear safety strategy.
