As heatwaves and drought restrict power generation across Europe, the BWRX-300 technology offers something increasingly valuable: reliable nuclear energy with cooling systems that require much less water and can be adapted to a world of lower river flows and higher temperatures.
When temperatures rise and electricity demand reaches its peak, Europe needs its most dependable power plants to be available. Yet this summer, the opposite has happened. Record-low river levels and exceptionally warm water have reduced nuclear generation in Romania, Hungary and France. The problem is not nuclear energy itself. It is that much of Europe’s existing power infrastructure was designed around climatic and hydrological conditions that can no longer be taken for granted.
Events of this summer
Hungary faced severe physical constraints as Danube levels fell. The Paks nuclear power plant, responsible for more than 40% of the country’s electricity, reduced generation dramatically. By early August, only one of the plant’s turbines remained in operation, producing approximately 240 MW, and the facility was running at around 10% of its normal capacity. A temporary increase in the river level prevented an immediate full shutdown, but the risk remained.
Hungary asked households and companies to reduce electricity consumption and prepared to increase imports. Large industrial consumers joined voluntary demand-reduction measures as high temperatures continued to drive air-conditioning use.
Downstream, in Romania, the consequences of low water levels were immediate when the Danube reached a critical point. Unit 1 (706 MW reactor) at the Cernavodă nuclear power plant was disconnected from the grid after the Danube fell to historically low levels. The two units normally account for around one-fifth of Romania’s electricity production.
At the Romanian entry point, the Danube was flowing at only around 35% of its July average — approximately 65% below normal. The disruption came as the heatwave increased electricity use, with peak demand estimated at 7.3 GW while domestic production had already fallen well below its normal level.
The Romanian government declared a nationwide state of emergency for August and funded emergency works intended to redirect water towards the remaining cooling infrastructure. It also sought additional electricity imports from neighbouring countries to cover periods of peak consumption.
The contradiction could hardly be clearer. Heatwaves increase the need for electricity while simultaneously reducing the availability of the plants expected to provide it.
France’s experience shows that the issue is not limited to rivers becoming too shallow. Nuclear plants can also face restrictions when rivers become too warm to receive the heat discharged during electricity production. Environmental rules limit the amount by which a plant may raise the temperature of surrounding water in order to protect aquatic ecosystems.
During the July heatwave, high river temperatures and low flows contributed to the unavailability of approximately 3.65 GW of French nuclear capacity. Reactors at sites including Golfech, Bugey and Chooz were shut down or had their output reduced, while France recorded its hottest July since national temperature measurements began in 1900.
Lessons learned
The lesson is not that Europe should move away from nuclear energy. It is that new nuclear capacity must be engineered for the climate in which it will operate over the next 60 years.
The BWRX-300 technology offers a solution. It can be configured with a range of heat dissipation systems, including mechanical-draft cooling towers, hybrid cooling and dry cooling. Where mechanical-draft cooling is selected, the plant can avoid the massive natural-draft towers associated with conventional nuclear facilities, which can lower construction costs. Instead of tying every project to the continuous availability of large volumes of river, lake or seawater, the cooling system can be selected to reflect the climate, water conditions and environmental requirements of an individual location. That flexibility is becoming a matter of energy security. A BWRX-300 equipped with dry cooling can reject heat primarily through the air, significantly reducing its operational dependence on river water. This would not make the plant immune to every effect of extreme heat, and site-specific engineering would remain essential. But it could sharply reduce one of the most immediate climate-related threats to Europe’s energy security: the loss of reliable generation when rivers run low or become too warm.
The technology also addresses a second, equally important question: how a reactor remains safely cooled if conventional plant systems or external water sources become unavailable.
The BWRX-300 uses passive isolation condensers located in dedicated pools within the seismically qualified reactor building. The system can shut down the reactor, remove decay heat and maintain it in a safe condition for seven days without electrical power or operator intervention. The cooling period can be extended by replenishing the isolation-condenser pools. Its core safety functions therefore do not depend on continuously returning water to a river, lake or ocean.
These are two separate but complementary advantages. Dry or hybrid cooling can make normal electricity production less vulnerable to declining river flows. Passive safety systems provide an additional layer of resilience when the reactor is shut down or conventional systems are unavailable. Together, they demonstrate what climate-resilient nuclear design can look like.
As policymakers across Europe assess how to strengthen energy security in the face of rising temperatures, changing rainfall patterns and growing pressure on water resources, cooling resilience will increasingly need to form part of decisions on new generating capacity. SGE is ready to work with governments, regulators and industrial partners in countries like Romania and Hungary to evaluate how the BWRX-300 could contribute to their future energy systems.
Through its European deployment platform, SGE combines a standardized reactor design and fleet-based approach with site-specific engineering, including the selection of cooling systems suited to local hydrological and environmental conditions. This is supported by regulatory cooperation, structured project development, financing solutions and the involvement of domestic supply chains. The objective is to ensure that new nuclear projects are designed from the outset for the conditions in which they will operate over the coming decades. As European decision-makers consider the next generation of reliable, low-carbon infrastructure, SGE is ready to offer a practical pathway towards resilient solutions for a changing world.
