Hungary was forced to shut down most of the Paks nuclear power plant — the country's only nuclear facility — after the Danube river dropped to record-low levels. The plant needs river water to stay cool, and there was not enough to keep it running safely. This has never happened in the plant's 44-year history.

A severe heatwave is gripping Central and Southern Europe. Budapest and Vienna are forecast to reach 37°C (about 99°F) on August 3, 2026. Cities including Zagreb, Rome, Tirana, Bucharest, and Paris are all seeing temperatures above 33°C (91°F). The heat is expected to last up to five days.

Paks produces a large share of Hungary's electricity. The plant runs four reactors that use water from the Danube to carry away excess heat — think of it like a car radiator that needs a steady flow of water to keep the engine from overheating. With the river level still falling, the plant was expected to be fully powered down later that week. Reuters reported on August 1 that the second-to-last unit still running would be shut, following an earlier warning from Prime Minister Péter Magyar that a complete shutdown was possible that weekend.

The shutdown has a big impact on power supply. According to the plant operator's own documentation, a full closure would remove about 2,000 megawatts of generating capacity from Hungary's system, with an additional loss of roughly 4,000 megawatts expected across the wider grid. Those numbers show how central Paks is to keeping Hungary's lights on.

The problem extends beyond Hungary. Romania and Serbia reported their lowest-ever river water levels in early August 2026, which disrupted hydroelectric power — electricity generated by water flowing through dams — across the lower Danube region. The same drought drying up the river at Paks is also cutting output from those dams downstream, worsening the regional energy shortage just when people need power most for air conditioning.

Hungarian authorities acted quickly to reduce consumption. On August 3, many digital advertising screens across the country were switched off as part of a broader energy-saving effort. Prime Minister Magyar warned that "the hardest five days are ahead."

The plant is built to shut itself down automatically if any of its systems are damaged, and backup safety systems remain available. The plant's water supply comes through steel pipes laid in tunnels and partially buried sections, as documented in a Hungarian Atomic Energy Authority (OAH) expert review. A 2020 OAH memo had already noted that under similar river conditions, planned new reactors at the site would need to run at reduced power to stay safe.

The broader context here extends beyond the immediate crisis. The Paks shutdown reveals a built-in weakness in nuclear plants that rely on rivers for cooling: as droughts become more frequent and intense across Central Europe, these plants have less and less safety margin. Hungary's 10th National Report on Nuclear Safety references the KNPA fund, set up to cover the eventual cost of taking the plant out of service. This event is not a shutdown-for-good scenario — the plant's safety systems are working as designed — but it is a real-world test of the assumptions behind both the current plant's operating limits and the case for building new reactors. If low river levels become more common, the reduced-output plans mentioned in that 2020 memo could go from a rare precaution to a regular limitation, affecting how much electricity the plant can reliably produce.

This is not just Hungary's problem. The hydropower disruptions in Romania and Serbia show that the Danube's water stress affects the entire river basin, hitting different types of power generation across several countries at the same time. For European energy planners, this event brings a question into sharp focus: do current safety tests and grid models fully account for how river levels, nuclear cooling, and hydropower are all connected? The fact that Paks ran for 44 years without a drought-related shutdown makes this a significant data point, even if the policy response will take months to work out.