Ukraine's blackouts: are her nuclear power plants in danger?

Friday 13 February 2026

Ukraine’s winter blackouts have become so routine that she sometimes feels like a country living on a timer switch—two hours of light, two hours of darkness, then a brief return to normality before the next interruption. The question that sits behind every candlelit kitchen and every generator-hummed stairwell is sharper than mere inconvenience: if the grid cannot be trusted, can Ukraine’s nuclear power plants (and nuclear sites) still be operated safely?

The reassuring answer is that Ukraine’s nuclear facilities are designed for precisely this sort of contingency—loss of external power is a standard design-basis event, with layers of redundancy. The unsettling answer is that the war has turned an event once treated as exceptional into something approaching a recurring condition, particularly at the occupied Zaporizhzhia Nuclear Power Plant. The safety margins remain, but the number of times Ukraine is forced to rely upon them has increased, and that is what changes the risk.

Nuclear power stations need electricity to be safe

A nuclear power plant is not safe because it produces electricity; it is safe because it can continuously remove heat from nuclear fuel and keep essential instrumentation, control systems and physical protection functioning. Even when a reactor is shut down, the fuel continues to generate decay heat. Cooling systems, valves, pumps, monitoring equipment, communications and security all require electricity.

That creates a paradox that is not widely understood outside the industry: a nuclear power station is, in part, an electricity consumer. It must power itself to remain safe.

Under normal conditions, that electricity comes from the grid via “off-site power” lines feeding the plant’s internal systems. If off-site power is lost, the plant relies on on-site emergency systems—batteries for immediate bridging, and emergency diesel generators (EDGs) for sustained supply. The IAEA has repeatedly underlined that dependence on EDGs is the “last line of defence” and that frequent losses of off-site power are deeply concerning because each one increases nuclear safety risk. 

So can a nuclear power plant “supply power to itself”?

Sometimes—and only in specific conditions.

If a reactor is operating and generating electricity, the plant can feed its own “house loads” (its internal safety and operational systems) from its generator. In many designs, the station can run in a sort of islanded or self-supplying mode for limited periods. However this is not the same as being independent of the grid in the way a household generator is independent of the street supply. A large nuclear unit normally depends upon the grid for stability, for dispatching power, and crucially for starting up. In practice nuclear stations are not considered “black start” resources in the way some hydro or certain thermal plants can be.

If a reactor has shut down—whether deliberately or because the grid is unstable—the station is no longer producing electricity. At that point it cannot “power itself” from its own generator. It must receive off-site power from the grid or use on-site emergency sources.

This distinction matters in wartime Ukraine, because grid instability and damaged substations can force nuclear units to reduce output or disconnect, which then increases reliance on those back-up systems. The European Union’s diplomatic service has explicitly linked damage to the power system with operational constraints at Ukraine’s operating nuclear plants, noting recent forced power reductions. 

What the blackouts are doing to Ukraine’s operating plants

Ukraine’s three operating nuclear sites—Rivne, Khmelnytskyi and South Ukraine—have not been operating in a vacuum. They are tied into a national transmission system that has been repeatedly struck. When key substations or high-voltage lines are damaged, operators may have to reduce reactor output, not because the reactor is unsafe, but because the grid cannot reliably accept or balance the electricity.

The IAEA has reported precisely this dynamic: attacks damaging infrastructure “key to nuclear safety” and disruptions to external power lines, with units reducing output as a result. In January 2026, Ukrainian reporting also described a significant drop in nuclear generation contributing to wider grid stress during a major disturbance—illustrating how tightly coupled nuclear output and transmission stability are. 

This is the central point: for Ukraine’s operating plants, the blackout problem is less that they are minutes away from catastrophe, and more that they are being pushed into a less efficient, more operationally constrained posture—ramping down, holding steady at reduced output, and managing a grid that is repeatedly injured. Every time an external line is lost, the plant moves one rung closer to needing emergency arrangements, even if it never reaches them.

Zaporizhzhia is the special danger

If Ukraine’s operating plants are a story about resilience under strain, Zaporizhzhia is a story about abnormality becoming routine.

Zaporizhzhia, Europe’s largest nuclear power plant, has been under Russian control since March 2022 and is not generating electricity. That single fact makes the question of “self-supply” far more acute. Because it is not producing power, it depends on external electricity to run cooling and safety functions. When that off-site supply is cut, the plant must fall back upon emergency diesel generators.

The IAEA and multiple reporting streams have documented repeated full losses of off-site power at Zaporizhzhia since the invasion, including prolonged periods running on diesels.  Reuters reported the IAEA’s description of the situation as “extremely precarious” after another complete loss of external power in 2025. An IAEA update in late 2025 described emergency diesel generators automatically starting to supply essential electricity during an external power loss—exactly as designed, but under conditions that should not be repeatedly tested in a war zone. 

There is a deeper reason Zaporizhzhia is different. When a nuclear station is shut down and isolated, time becomes the currency of safety: diesel fuel stocks, generator reliability, maintenance under hostile conditions, and the ability to repair external lines. The longer off-site power is absent, the more the plant’s safety rests on logistics and mechanical luck rather than robust infrastructure. Even where generators are available, they are not meant to substitute for the grid for weeks at a time. One month-long outage was widely described as record-breaking and emblematic of the new abnormal. 

Chornobyl is not a power plant, but it is a nuclear site with real needs

Chornobyl often sits in the public mind as a historical symbol rather than an operating facility. Yet the site includes spent fuel management and the New Safe Confinement—systems that still require reliable electricity for monitoring, ventilation and other safety-related functions.

In January 2026 the IAEA reported that the Chornobyl site lost all off-site power during military activity, later relying on emergency diesel generators for about an hour. Ukraine’s authorities stated that the site was reconnected and that radiation levels were normal. 

This episode is instructive. It shows that blackouts can reach nuclear sites beyond the operating reactor fleet—and that even “non-generating” sites can be pushed onto emergency arrangements when the wider energy system is attacked.

Are the blackouts putting safe operation in danger?

They are increasing risk, but not in a simple, cinematic way.

In nuclear safety, “danger” is often misheard as an immediate cliff edge. The reality is more subtle. Each loss of off-site power is a step down a ladder of defence-in-depth: from normal grid supply, to alternative grid lines, to on-site diesels and batteries. Ukraine’s operating plants generally retain multiple external lines and established emergency procedures, and the IAEA’s on-site presence and reporting add a measure of transparency, even in wartime. 

But war changes the statistical landscape. Events that were assumed to be rare—multiple grid disruptions, repeated damage to substations, long repair times under fire—are no longer rare. The IAEA has explicitly pointed to the vulnerability of crucial substations and the way damage to them undermines nuclear safety. And in Zaporizhzhia’s case, repeated full external power losses have become a grim pattern rather than an anomaly. 

So the most defensible conclusion is this:

• Ukraine’s operating nuclear power plants are not helpless during blackouts—they have robust emergency systems, and they can usually keep their own essential systems powered through off-site redundancy and, if necessary, on-site generators.

  
  

• However they cannot assume infinite self-sufficiency. If a unit is shut down, it cannot generate its own electricity, and prolonged loss of off-site power would progressively shift the burden to emergency equipment and fuel logistics.

  
  

• The greatest safety concern remains the occupied Zaporizhzhia site, precisely because it is not producing power and because external power has been repeatedly severed, forcing reliance on emergency diesels for extended periods. 

In other words, the blackouts are not merely a civilian hardship running parallel to the nuclear story. They are part of the same strategic contest. Russia’s campaign against Ukraine’s energy system does not need to strike a reactor containment dome to create nuclear risk; it only needs to keep degrading the web of lines and substations that allow nuclear facilities to live in their normal, stable state.