Cernavodă’s nuclear margin shrinks to 11cm

The water level at Cernavodă's intake basin read about -218 cm on 7 August (Newscenter). Operators must shut down Unit 2, Romania's last running nuclear reactor, if the level drops to around -229 cm (Capital). That is an 11-centimetre margin, and according to the same monitoring reports the river has been falling 2–3 cm a day.

Romania warned Brussels and all EU governments under Regulation 2019/941, EU rules that require countries to flag power-supply risks that could spill across borders (Europa FM). The alert gets everyone watching. It does not deliver a single megawatt.

Why a falling river shuts a nuclear plant

Cernavodă's reactors use Danube water to cool their condensers, the equipment that turns steam back into water after it has driven the turbines. No water flow, no cooling, no power. Unit 1 was already disconnected on 28 July when flow dropped to about 1,630 cubic metres per second, far below the August average of roughly 3,900 (Agerpres, HotNews).

Since then Romania has blasted a rock formation, dredged the channel and prepared to sink barges to redirect flow. The rock blast raised levels by about 2 cm (Euronews România). Nuclearelectrica technical director Emil Macovei said the barge work could buy two to three more days, but if the decline continues, Unit 2 will probably stop after that (Digi24).

The neighbours who could help need help too

Unit 2 produces roughly 680 MW, about 8–9% of Romania's evening peak demand, which the heatwave has pushed toward 8,000 MW (Europa FM). Romania was already importing about 1,700 MW at evening peaks. If Unit 2 stops, the import need could exceed 2,500 MW (Financial Intelligence).

The countries that would normally supply that power sit on the same river. Hungary's Paks plant fell to roughly 480 MW from its normal 2,000 MW in early August, forcing Hungary itself to import power and tap gas reserves (Pénzcentrum, MVM).

Bulgaria has been the clearest lifeline. On 7 August morning it was exporting 1,355 MW to Romania, drawing on solar and coal (economic.bg). But Bulgarian officials said export capacity had been "fully used" in recent days (Bulgarian Energy Ministry), and Kozloduy's nuclear reactors depend on the same falling Danube.

Who gains, who pays

Traders and flexible generators selling scarce evening power are the short-term winners. Day-ahead prices across Central and Southeast Europe already show premiums driven by the Paks and Cernavodă stress (Serbia Energy).

The immediate losers are Nuclearelectrica's customers. The company warned them it may not be able to meet delivery contracts, claiming force majeure, the legal argument that an extraordinary outside event prevents a company from fulfilling its obligations (ZF). Industrial consumers face voluntary or mandated demand cuts well before households see any retail-price change. Transelectrica, Romania's grid operator, asked large users to keep consumption low to avoid a major grid failure (Mediafax).

Energy Commissioner Dan Jørgensen described the EU's Electricity Coordination Group as a forum for sharing information (Dan Jørgensen). Europe's electricity market normally lets power move to wherever it is scarce. The problem this drought exposes is that Romania, Hungary and Bulgaria all need extra power during the same evening hours, and the river that cools their plants is the same river that is running dry.