While Romania uses explosive detonations to save the Cernavodă nuclear plant and Hungary's Paks avoids forced shutdown, the Croatian-Slovenian power plant has a more modern cooling system.
The heatwave that has hit Europe has brought record-low river levels, threatening the operation of nuclear power plants across the region. While Romania takes unprecedented measures to save its nuclear plant, and Hungary's Paks barely avoided a forced shutdown, nuclear energy expert Tonči Tadić from the Ruđer Bošković Institute in Zagreb points out that the Krško Nuclear Power Plant (NEK) is in a significantly better position thanks to decisions made half a century ago.
The Romanian government declared a state of alert during August due to a drop in electricity production caused by drought. Last week, the state-owned company Nuclearelectrica, which normally generates about 20% of Romania's electricity, had to shut down one of the two reactors at the Cernavodă nuclear plant because there was not enough water for cooling.
To increase the flow of water from the Danube towards the plant, Romania carried out a controlled explosion on the Pârjoaia rock formation on Sunday and Monday (August 2-3, 2026). The operation involved one hundred members of the Romanian armed forces and 16 experts, using more than 180 kg of explosives. Rear Admiral Marcel Neculae, deputy chief of staff of the Romanian Navy, said the aim was to divert part of the water from the Bala branch to the Old Danube, from where the Cernavodă nuclear plant draws its cooling water.
After the explosion, dredging of the riverbed was carried out on Tuesday and Wednesday (August 3-4). There are also plans to sink barges filled with stones in the Bala branch to further increase the flow towards the Old Danube. This action comes as the Danube's flow at the entrance to Romania is expected to drop to about 1,400 cubic meters per second in the coming days, close to the record low from 1985 and nearly three times less than the August average.
The government has appealed to citizens and businesses to voluntarily reduce electricity use during evening peak hours. Car manufacturers Dacia (owned by Renault) and Ford have agreed to halt production at their plants in Romania until August 19, voluntarily cutting electricity consumption by about 200 megawatts.
On Monday (August 3), the Paks nuclear plant in Hungary was nearly forced to shut down due to historically low Danube water levels, but that scenario has been avoided for now. Zoran Đuroković, director general of Hrvatske vode, warned on N1 on Tuesday about the extremely low water levels of all rivers in Croatia. In the past few days, the lowest Danube water levels since 1909 have been recorded, and the Drava in Osijek is only three centimeters from its historical minimum.
Although NE Krško also faces low flow and elevated temperatures of the Sava River, Tadić emphasizes that the situation is significantly different. "These two nuclear plants in Hungary and Romania and Krško are on different rivers, and there is an attempt to project a problem that does not exist," he said for N1.
"NE Krško has cooling towers, which greatly secures the situation. These are things that are taken into account when building a nuclear plant, not when such problems arise. It is much cheaper to build a nuclear plant without them, but it is a matter of responsibility. When the construction of NE Krško began (mid-1970s, note), the then representatives of Croatia and Slovenia insisted on a modern cooling system that would not overheat the Sava nor depend on thermal oscillations like we have now. That is the difference between Krško and the nuclear plants in Hungary and Romania. Krško is in a much better position because it was taken care of in time," says Tadić.NE Krško issued a statement on Monday saying it is operating at full reactor power, with cooling towers in operation and compliance with restrictions related to the Sava River. The plant must ensure that the daily average temperature of the Sava at the point of complete mixing downstream from the Brežice Hydroelectric Plant does not exceed 28°C, and the average daily temperature increase must not exceed 3°C.
For the plant to operate smoothly, the Sava River flow must be 25 cubic meters per second. On Tuesday around 1 p.m., the flow was 49.4 cubic meters per second, twice the prescribed amount. However, on Monday around 1 p.m., the water temperature increase was 2.6 degrees Celsius, approaching the maximum allowed limit of 3°C.
At the Čatež I measuring station, relevant for NE Krško, the Sava water level varied over the past days from 62 centimeters on Saturday (August 1) to 56 centimeters on Sunday and Monday (August 2-3), before reaching 62 centimeters again on Tuesday. The highest Sava temperature at that station was 31.5°C on Sunday, 28.8°C on Monday, and 27.9°C on Tuesday at 1 p.m.
NEK has informed the authorities that it is approaching a situation where, due to environmental restrictions, it will have to reduce reactor power, and in the worst case, gradually shut down the plant. Tadić, however, sees no reason for alarm. "We will just have to take into account that there will be more heatwaves and that nuclear plants will need to address this with cooling towers. It is nothing unusual. Most nuclear power plants and even thermal power plants have this technology," he concludes.
