Kozloduy NPP operates stably despite the drop in the Danube's water level

The water level of the Danube River continues to decrease, and in the Bulgarian section near Ruse, a value of minus 91 centimeters relative to the conditional zero mark was measured today. This represents a drop of two centimeters compared to the previous day, and a further decline of about three centimeters is expected in the coming days.

The Ministry of Energy states that no significant limitation of the production capacity of the Kozloduy NPP is expected over the next three weeks. Both operating units of the plant continue to function in normal mode, regardless of the falling river level.

Energy expert Prof. Yanko Yanev clarified a common misconception about the way the reactor is cooled. "Ordinary people sometimes think that water from the Danube flows through the reactor – no, it does not flow through the reactor," he pointed out.

In fact, river water is used via pumps and a gravitational channel solely for cooling the steam in the condensers – a system entirely separate from the nuclear reactors themselves. Both Kozloduy NPP and the Ministry of Energy confirm that the available water resource is sufficient, even if the river's decline continues at the same pace for at least the next three weeks.

"This danger, at least for the moment, does not face the Kozloduy plant, as it still has a sufficient reserve in the cooling water level to properly cool the plant," stated Prof. Yanev.

However, the situation is different for neighboring nuclear power plants. The low river level has already caused difficulties in the operation of the Hungarian Paks NPP and the Romanian Cernavodă NPP, which carries a risk of tension in the regional energy market and a possible need for electricity savings.

"It is more than certain that every country will strive to preserve its own electricity transmission network," the energy expert commented regarding the expected reaction of the states in the region.

Currently, more than 30% of the electricity produced in Bulgaria comes from the Kozloduy NPP, while photovoltaic plants provide about 40%. Solar energy, however, cannot completely replace turbine-based production, as this would disrupt the energy balance of the system.

Prof. Yanev also explained the technological limitations of solar installations. "Photovoltaic plants produce a fixed voltage, and from that point on, if the frequency changes, their systems will shut down the entire plant so it doesn't burn out," he pointed out.

It was precisely the disruption of such an energy balance that led to the total blackout that paralyzed Spain and Portugal in April 2025. To avoid such scenarios, it is key to maintain the sustainable participation of electricity produced through turbines.