Record low Danube river levels have sharply disrupted nuclear generation in Hungary and Romania, underscoring how extreme heat and drought are complicating the operation of reactors that rely on river water for cooling. Hungary earlier this month cut output at its 2-gigawatt Paks nuclear plant to just over 10% and has since raised it to 25%, narrowly avoiding a first full shutdown in 44 years. Romania’s state-owned Nuclearelectrica shut its last working reactor on Thursday after attempts to divert more cooling water proved insufficient. The strain comes as both countries still see nuclear power as a key source of domestic, low-carbon baseload electricity, even as climate pressures expose a vulnerability in traditional cooling systems. Scientists and water engineers have warned that Central eastern Europe is becoming drier and that Danube flow patterns may turn more extreme and volatile, increasing the risk of similar disruptions. Governments are now weighing emergency and longer-term responses. Prime Minister Peter Magyar said Hungary would build a riverbed sill (a submerged dam-like structure) to raise water levels, and two barges could be sunk on Friday to help prevent a shutdown as the river is expected to fall further. Hungary is also reviewing cooling assumptions for the planned Paks 2 expansion. In Romania, a 1.02 billion lei ($225 million) project approved in 2024 aims to reshape the Bala branch of the Danube system to improve water management, though it has been delayed. Nuclearelectrica said studies show that project would allow four reactors to run at full capacity, while analysts say additional cooling options may also need to be considered.