Low Danube Water Levels Impact Nuclear Power Plant Operations in Romania and Hungary

On August 4, amid persistently low Danube River water levels, Romania was rushing to build temporary dikes to divert more river water toward the Cernavodă Nuclear Power Plant to secure cooling water for its remaining operational reactor. Meanwhile, Hungary stated that the only still-operating turbine unit at the Paks Nuclear Power Plant was running in a safe condition.

Both Hungary's Paks Nuclear Power Plant and Romania's Cernavodă Nuclear Power Plant rely on Danube River water for cooling. Recently, the Danube's water level dropped to historic lows, leading to a significant decline in nuclear power output in both countries. Budapest and Bucharest have had to increase electricity imports and call on residents and businesses to reduce consumption to ease grid pressure.

Romania's state-owned nuclear power company, Nuclearelectrica, typically supplies about one-fifth of the country's electricity. Affected by declining river water levels, the company shut down one of the two reactors at the Cernavodă Nuclear Power Plant early last week.

In Hungary, three of the four turbine units at the Paks Nuclear Power Plant have been taken offline, and the plant is currently operating at just over 10% of its installed capacity. Local authorities are closely monitoring Danube water levels to avoid a forced shutdown of the last operational unit.

Hungarian Prime Minister Péter Magyar said that around 1:30 a.m., the water level relevant to the intake at the Paks Nuclear Power Plant, located south of Budapest, came within just a few millimeters of triggering a full shutdown condition, before the decline stopped and the level recovered by about 1.5 centimeters by morning. He later said in a video released at the plant that significant rainfall might occur in Austria's catchment area around Thursday, but whether it would effectively replenish the Danube remained uncertain.

Romania's national water management authority is building a temporary dike in a tributary of the Danube. The construction method involves sinking four barges loaded with rocks into the riverbed to alter the flow direction and divert more water toward the Cernavodă Nuclear Power Plant.

On August 3, the Romanian Navy blasted away a rock outcrop to facilitate water flow and create conditions for sinking the barges. Local officials said the dike project is expected to be completed by Wednesday or Thursday. Nuclearelectrica executive Romeo Urjan said that after removing the rock obstruction, the operating time of the remaining operational reactor at the Cernavodă Nuclear Power Plant is expected to be extended by about seven days.

To reduce grid load, Hungarian households and more than 300 businesses have responded to the government's call to voluntarily cut electricity consumption. Hungarian power company Magyar warned that, with the continued heatwave, this week remains a critical phase for electricity supply. The Hungarian government has not yet imposed mandatory restrictions on industrial power use, but has not ruled out such measures if the situation deteriorates.

Romania has also called on households, businesses, and public institutions to reduce electricity consumption. Austrian wood panel manufacturer Kronospan said it would phase out some of its production lines in Romania, cutting its electricity use in half. Planned maintenance and summer production halts at French automaker Renault's subsidiary Dacia and at Ford Otosan Romania are also expected to further reduce local electricity demand.

Elsewhere in the region, Polish grid operator PSE on Tuesday evening called on power generators to fulfill capacity obligations and strengthen reserve generation capacity to cope with heat-driven electricity demand pressure. PSE had previously said that high temperatures and low water levels had limited the operation of some power plants, but that the power system was prepared for summer demand.