Romania Loses a Fifth of Its Power as Danube Starves Nuclear Plant

About a fifth of Romania's electricity vanished in a single morning. That is the scale of what happened when the country's only nuclear power plant, Cernavoda, went fully offline, leaving a gap normally filled by two large reactors to be covered by other generation and imports during summer heat ⁸⁹. For a power system that counts on steady nuclear output as its backbone, losing that share at once is not a maintenance blip. It is a system-wide stress test.

Unit 2, the plant's last operating reactor, began a controlled shutdown on the morning of Thursday, 13 August 2026, with power reduction from 8:00 AM and disconnection from the grid from 11:00 AM, just before midday ¹⁰. Operator Nuclearelectrica announced the move that morning as a controlled shutdown tied to conditions on the Danube ¹⁰. The timing matters because the aired video described the shutdown as happening on 14 August, but primary reporting dates the Unit 2 disconnection to 13 August, with the full-plant-offline report following on 14 August ²³⁵¹⁰⁴.

The outage did not arrive suddenly. Unit 1 had already been disconnected from the National Energy System on 28 July ⁵. World Nuclear News reported that shutdown as driven by unprecedentedly low water conditions on the river ⁵. For more than two weeks, Romania therefore ran with half its nuclear fleet down before the second unit followed, turning a partial loss into a complete one.

Each of Cernavoda's two CANDU reactors is rated at 706 MW ²⁸. Together they normally supply about a fifth of Romania's electricity ⁸⁹. That arithmetic explains why the loss of one unit in July was serious and the loss of both in August was consequential: roughly 1,400 MW of firm, round-the-clock capacity had to be replaced at a moment when heat tends to push demand higher and strain other parts of the system.

Cooling water for Cernavoda comes entirely from the Danube ⁶. When prolonged heat drove river levels to record lows, the plant lost the margin it needs for safe operation. One specialist report put the trigger in concrete terms, saying the Danube fell below the plant's 185-centimetre operating threshold ⁷. A nuclear plant does not negotiate with that kind of limit. Without assured cooling water at the required level, the only safe choice is to reduce power and then disconnect.

The operator's public outlook on restart was cautious, with Nuclear Engineering International quoting the company as saying it did not foresee a restart within the immediate period covered by its statement ⁸. The full wording of that statement was truncated in the available reporting text, so the precise window should not be overstated beyond what the sources preserve. What is clear is that restart was not presented as imminent, leaving Romania exposed for as long as heat and low water persisted.

With both reactors dark, Romania was obliged to import more electricity to help cover the shortfall ⁹. Balkan Insight framed the moment as a deepening power crisis rather than a brief technical outage ⁹. Imports can bridge a gap, but they do so at the market's price and on neighbours' availability, which is an uncomfortable position when a heat-driven drought is basin-wide rather than local.

The basin-wide character is essential. Hungary, facing the same river crisis on the same Danube, moved to keep its Paks nuclear plant operating through emergency measures ⁵. Reporting describes barges and riverbed works as part of that effort, alongside controlled explosions and other riverbed interventions discussed by Romanian and Hungarian authorities in response to the low water ⁵⁶¹¹. The available sources place those barge and riverbed operations in the Hungarian and Paks context ⁶¹¹. They do not establish that rock-loaded barges were sunk at Cernavoda's own intake, and that distinction should be kept.

This was not presented as a reactor failure or a safety incident inside the plant. It was a controlled response to an external condition the plant cannot control. That is in some ways more sobering for energy planners than a broken part, because a part can be repaired on a schedule. A river recovers only when rain and upstream flows return, and prolonged heat across southeastern Europe gave little assurance of quick relief.

What remains is a waiting game measured in centimetres. If the Danube rises back above safe operating levels, Cernavoda can begin the careful path back to power. If it does not, Romania must continue to replace nuclear output from elsewhere while watching the same heat that emptied the river push demand upward. The sources do not support broader claims sometimes attached to this shutdown, including that it was the first full outage since a particular year or that a specific share of the Danube set a particular multi-decade record. What they do support is stark enough: record-low water, two 706 MW units offline, about a fifth of national electricity to replace, and no quick fix while the river stays low ²⁴⁷⁸⁹.