Romania’s Cernavodă nuclear plant shuts both reactors as Danube flow hits 1,600 m³/s, losing a fifth of daily power

Reactor shutdowns and river levels

Romania’s Cernavodă nuclear power plant, the country’s sole nuclear facility, lost both of its operating units within 48 hours after the Danube’s flow dropped to levels that no longer allowed safe cooling-water intake. Unit 1 was taken offline in a controlled procedure on 28 July, and operator Nuclearelectrica announced on 29 July that Unit 2 would follow, either late that evening or by 10:00 on 30 July, depending on the river’s continued decline. It is the first time both reactors have been shut simultaneously because of low water.

Similar to the shutdown of Unit 1, Unit 2 will be shut down in a controlled manner due to the extremely low, unprecedented level of the Danube, caused by severe drought, in accordance with the plant’s procedures applicable in severe drought situations.

Interim Prime Minister Ilie Bolojan told Digi24 that the Danube’s flow at the plant intake had fallen to 1,600 cubic metres per second, less than half of the 3,900–4,500 m³/s normally recorded in summer months. "They are less than half of the Danube’s flow in a normal period," he said, adding that the pumps that draw cooling water must be stopped when the level drops below two metres. The National Institute of Hydrology and Water Management (INHGA) forecasts that the flow at the Baziaș entry section will fall further to about 1,500 m³/s between 29 July and 5 August, far below the multi-year July average of 4,700 m³/s.

Impact on the national grid

Together, the two Cernavodă units supplied roughly 1,300 MW of baseload power, close to 20 % of Romania’s daily consumption of approximately 7,000 MW. With both reactors offline, the country has lost what energy experts call a "secure capacity," available around the clock regardless of weather. Dumitru Chisăliță, president of the Intelligent Energy Association, described the situation as "critical, but manageable." Romania must now push domestic thermal, gas, coal, hydro, wind and solar generation to maximum output while significantly increasing electricity imports.

Evening hours, especially between 20:00 and 23:00, are the most strained. Bolojan noted that the country was already importing about 1,700 MW during the evening peak on 29 July and would need to import "a somewhat larger quantity." Chisăliță estimated that peak imports could climb to 3,000–3,200 MW, very close to the maximum import capacity on Romania’s western and southern interconnections.

Price consequences for the market

The loss of the nuclear baseload and the forced reliance on expensive peak-hour imports have already caused sharp increases in day-ahead electricity prices. Chisăliță pointed out that the spread between the lowest and highest hourly price on the next-day market (PZU) was set to widen to a factor of 25 on 30 July, up from a previous record of 23.

From a price perspective, tomorrow we will have the largest difference between hourly prices. If the last big difference was 23 times between the lowest and highest price in a day, tomorrow we will have 25 on the day-ahead market. And frankly, I expect the day after tomorrow the peak-hour prices will be even higher.

He warned that the trend is unlikely to reverse quickly and that consumers will eventually feel the effect on their electricity bills.

Government appeal for conservation

Addressing the public on 29 July, Bolojan urged households and large industrial consumers to voluntarily reduce electricity use during the critical evening window.

I take this opportunity to make an appeal to the citizens of Romania, to the large industrial consumers, to consider the possibility of a voluntary reduction — simply to be careful how much they consume in the evening hours, from 20:00 to 23:00, when we have a deficit of energy.

He admitted that the crisis also reflects years of under-investment in new dispatchable generation. "Now we see what it means not to have made investments over the years," he remarked.

Outlook and drought forecast

With no significant rainfall forecast for the lower Danube basin, the drought-induced shutdown could last one to two weeks. Bolojan cautioned that import capacity might itself become strained if the drought affects neighbouring countries. One unit at Hungary’s Paks nuclear plant has already reduced output from nearly 2,000 MW to about 1,200 MW. Nuclearelectrica said it is continuously monitoring the Danube’s level and will reconnect the Cernavodă units only when hydrologic conditions allow safe operation.