Drought Is Turning Water Scarcity Into a New Risk for Europe’s Nuclear Power

Romania has shut down its entire nuclear power plant at Cernavodă after the Danube fell to record-low levels, exposing a vulnerability that could become increasingly important for Europe’s energy system. The second reactor was taken offline on August 13, after the first reactor had already been shut down at the end of July because there was not enough water available for cooling.

The two reactors at Cernavodă, each with a capacity of around 700 MW, normally provide roughly one-fifth of Romania’s electricity. Their simultaneous shutdown removes a major source of low-carbon baseload generation at a time when high summer temperatures are already increasing electricity demand. Romania is expected to compensate through imports and greater use of other generation sources, including hydropower, wind and coal.

The disruption also has regional consequences. Romania plays an important role in electricity supplies to neighbouring Moldova, while the wider southeastern European electricity market depends on cross-border flows to balance periods of high demand and limited domestic generation. Losing around 1.4 GW of nuclear capacity reduces the room for exports and increases pressure on regional electricity markets if extreme weather persists.

Nuclear power meets a changing climate

The Cernavodă shutdown highlights a contradiction at the centre of Europe’s energy transition. Nuclear power is increasingly viewed as a stable source of low-carbon electricity that can reduce dependence on fossil fuels and compensate for the variability of renewable generation. Yet many nuclear plants depend on large quantities of water for cooling, making them vulnerable to precisely the kind of extreme weather that climate change is making more frequent.

The problem has become particularly visible along the Danube. Romania has already resorted to extraordinary measures to preserve water flows towards Cernavodă. Earlier this month, authorities used controlled explosions to alter the riverbed and redirect more water towards the nuclear plant. The intervention was intended to keep the cooling system supplied as the river continued to fall. It ultimately proved insufficient to prevent the second reactor from being shut down.

Hungary has faced a similar challenge at the Paks nuclear power plant, which also relies on the Danube for cooling. The facility has had to reduce output as water levels and temperatures have reached critical conditions. Hungarian authorities have explored engineering measures to maintain sufficient water around the plant, including the construction of underwater barriers designed to raise local water levels.

The simultaneous pressure on nuclear facilities in two countries suggests that this is no longer simply a problem for individual plant operators. Low river levels are becoming an energy-security issue across the continent, particularly in regions where nuclear and industrial infrastructure is concentrated along major waterways.

The energy system is being squeezed from both sides

European energy planning has traditionally treated extreme heat primarily as a demand-side problem. Higher temperatures increase electricity consumption as households and businesses use more cooling. This summer is demonstrating that heat can also undermine the supply side.

For nuclear plants located along rivers, the pressure is particularly difficult to manage. As temperatures rise, electricity demand increases, while drought reduces the volume of water available for cooling. If river levels fall below operational thresholds, reactors may have to reduce output or shut down regardless of how much electricity the grid requires.

Water temperature adds another constraint. Even when sufficient water remains in a river, environmental regulations can restrict how much warm cooling water can be discharged back into the ecosystem. During prolonged heatwaves, this can further limit the operating capacity of thermal and nuclear plants.

The result is a potential feedback loop in which the weather simultaneously increases demand and reduces the availability of some of the generation needed to meet it.

The Danube is becoming an energy-security issue

The significance of the current crisis extends beyond Romania and Hungary because the Danube is much more than a source of cooling water. It is one of Europe’s most important waterways, supporting transport, agriculture, industry, drinking-water supplies and energy infrastructure across multiple countries.

The extreme drop in water levels is already affecting other parts of the regional economy. Lower river levels make navigation more difficult, increase transport costs and reduce the amount of cargo that vessels can carry. When the same hydrological conditions also constrain electricity generation, a single climate-related shock begins to affect several critical systems at once.

That raises a broader question for European infrastructure planning. Energy networks have increasingly been designed around the assumption that electricity can move across borders when individual countries face shortages. But if extreme weather affects several interconnected countries at the same time, regional markets may have fewer options for balancing supply.

Romania can replace some of its lost nuclear generation with imports. That strategy becomes considerably more difficult if neighbouring countries are simultaneously experiencing reduced hydropower production, constrained nuclear output or increased electricity demand caused by the same heatwave.

Adaptation is becoming part of nuclear policy

Romania is now looking for longer-term engineering solutions. Authorities have revived efforts connected with the Bala 2 project, which is intended to improve water flows towards Cernavodă and provide the plant with a more reliable cooling-water supply.

The crisis demonstrates why such infrastructure may become increasingly important for the future of nuclear power. Building a reactor is only one part of securing reliable nuclear generation. Operators must also ensure that the surrounding water system can continue to support the plant under increasingly extreme hydrological conditions.

That could influence where future European nuclear projects are built and how they are designed. Technologies that require less freshwater, alternative cooling systems, additional water reserves and more resilient intake infrastructure could become increasingly important considerations alongside construction costs, reactor technology and grid connections.

For existing plants, climate resilience may require significant investment as well. Infrastructure designed around historical river levels may not remain adequate if droughts become more frequent or last longer.

Europe’s nuclear expansion faces a new constraint

The shutdown at Cernavodă does not indicate a nuclear safety incident. The reactors are being taken offline because the available cooling water is insufficient. That distinction matters, but it does not make the event less significant for energy policy.

Europe is considering nuclear power as part of its long-term strategy for reducing emissions and strengthening energy security. Romania itself plans to expand its nuclear capacity, including through new reactors at Cernavodă. Yet the current crisis demonstrates that the reliability of nuclear generation cannot be assessed independently of the physical environment surrounding each plant.

The challenge is not simply whether Europe can build more reactors. It is whether the infrastructure supporting those reactors will remain resilient under conditions that were once considered exceptional.