Romania's Nuclearelectrica announced it will temporarily shut down the second reactor at the Cernavoda nuclear power plant on July 30, two days after Unit 1 was taken offline, leaving the country's sole nuclear facility without generation for several days as severe drought pushes Danube water levels to unprecedented lows.

Nuclearelectrica said the controlled shutdown of Unit 2 was required because of the "very low, unprecedented water level of the Danube". The reactors use Danube water for cooling, making the plant particularly exposed to low river flows. The two Cernavoda reactors normally cover nearly 20% of Romania's electricity demand during peak hours.

Based on current hydrological forecasts, Unit 1 is expected to resume production on August 4, while Unit 2 is scheduled to return on August 10, according to Economica. The latest forecast from the national company Romanian Waters and the Hydrology Institute INHGA, however, questions these expectations, as the Danube flow rate on August 4 is expected to be the same as currently, according to Mediafax.

First Danube-related shutdown in 23 years

The simultaneous shutdown of both units is the second such incident in several months, but it is the first time in 23 years that the Cernavoda plant has been forced offline because of the Danube's flow, according to Dumitru Chisăliță, president of the Smart Energy Association, in an analysis for Mediafax.

The situation is part of a broader regional impact from the low Danube level. Hungary has already reduced production at its Paks nuclear plant to prevent overheating, and Bulgaria's Kozloduy nuclear power plant could also face a shutdown if water levels continue to deteriorate, according to Ziarul Financiar.  Unlike nuclear plants in Slovakia and the Czech Republic, which use natural or artificial lakes for cooling, Cernavoda, Kozloduy and Paks depend on river water, leaving them exposed to drought-related restrictions.

Separately, Serbia has cut output at the Djerdap 1 hydropower plant to around one-third of its capacity, reported Reuters,

Djerdap 1, also known as Iron Gates 1, has an installed capacity of 1,000 MW for Romania and 1,000 MW for Serbia and accounts for roughly one-tenth of Romania's electricity output, adding to the pressure on the country's power system.

Romania to rely more heavily on imports

Acting Prime Minister Ilie Bolojan, who is also interim Energy Minister, speaking on July 29, said that Romania would activate all available generation capacity and urged households and industrial consumers to reduce electricity consumption during the evening peak between 20:00 and 23:00.

"We will have to bring online all capacities that we can use, namely gas-fired power plants, photovoltaic, storage, wind power, and also resort to imports," Bolojan told Digi24.

Notably, the coal-fired power plants supplied roughly 10% of domestic electricity consumption on July 29 and accounted for more than 10% during peak hours, when they produced around 900 MW against total consumption of approximately 7,000 MW.

Romania was already importing around 1,600 MW during peak hours on July 29, mainly from Bulgaria, while Cernavoda was still contributing approximately 680 MW, according to Transelectrica. The loss of that nuclear generation from July 30 will increase the country's reliance on imports and domestic thermal, hydro, wind, solar and storage capacity.

Imports from Bulgaria are expected to reach the available interconnection capacity during the evening peak. On the day-ahead market for delivery on July 30, the Bulgaria-Romania interconnection was already fully booked between 19:00 and 23:00, with imports exceeding 1,800 MW during the 20:00-23:00 period, according to the market operator OPCOM.

The traders booked the available capacity at prices above €150/MWh ($172/MWh), with some hourly segments approaching €350/MWh ($402/MWh), compared with a daily average of around €130/MWh ($149/MWh).

Higher costs likely to reach consumers

The Romanian power system is considered capable of managing the temporary loss of Cernavoda's output by using all available generation sources and imports, but the adjustment will come at a cost.

AEI expert Dumitru Chisăliță said consumers should not expect an immediate increase in electricity prices as a direct result of the shutdowns. However, the higher costs incurred by suppliers are likely to be reflected in future offers when existing contracts are renewed.

"We will not necessarily see an increase [in the electricity price] tomorrow or next month, but the situation we are witnessing generates costs that will be recovered by suppliers from future price offers," Chisăliță said.

He added that the disruption could also increase the risk premium incorporated into suppliers' offers as companies seek to protect themselves against the possibility of further supply disruptions.

"All this will most likely lead to increases in price offers in the market," the AEI president said.

The impact will therefore depend partly on how quickly the Danube recovers and whether the two Cernavoda reactors can return to operation according to the current timetable. For now, Romania's power system will have to operate without its source of nuclear generation while regional drought simultaneously limits some neighbouring countries' ability to provide additional electricity.