Danube Drop Threatens Cernavodă Reactor

By the morning of 7 August, Romania's room for manoeuvre at Cernavodă had become almost absurdly small. The water level at the plant's intake basin was about -218 cm (Newscenter). Unit 2, the country's last working nuclear reactor, has to be shut down if that falls to around -229 cm (Capital).

That leaves 11 centimetres between a strained power system and the loss of another reactor. The same monitoring reports say the Danube has been dropping by 2-3 cm a day.

Romania has now warned Brussels and every EU government under Regulation 2019/941, the EU rulebook for electricity-risk preparedness. In plain English, it is the mechanism that forces a member state to tell its neighbours when a power problem may cross borders (Europa FM). It gets the phones ringing across the system. It does not produce electricity.

Why a falling river shuts a nuclear plant

Cernavodă's reactors need Danube water to cool their condensers, the equipment that turns steam back into water after the steam has driven the turbines. Without enough flow, the plant cannot cool properly. Without cooling, it cannot generate safely.

Unit 1 was already taken off the grid on 28 July, when the flow fell to about 1,630 cubic metres per second, well below the August average of roughly 3,900 (Agerpres, HotNews).

Since then, the Romanian authorities have tried the kind of emergency engineering that tells its own story. They have blasted a rock formation, dredged the channel and prepared to sink barges to push more water towards the intake. The rock blast lifted the level by about 2 cm (Euronews România).

Nuclearelectrica technical director Emil Macovei said the barge operation could buy another two or three days. If the river keeps falling after that, Unit 2 will probably have to stop (Digi24).

The neighbours who could help need help too

Unit 2 generates roughly 680 MW, or about 8-9% of Romania's evening peak demand, which the heatwave has pushed towards 8,000 MW (Europa FM). Romania was already importing about 1,700 MW during evening peaks. If Unit 2 goes, that need could rise above 2,500 MW (Financial Intelligence).

The catch is that the countries most likely to help are fighting the same river. Hungary's Paks plant dropped to roughly 480 MW from its normal 2,000 MW in early August, leaving Hungary to import power and draw on gas reserves (Pénzcentrum, MVM).

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

Who gains, who pays

The immediate winners are traders and flexible generators able to sell scarce evening power into a stressed market. Day-ahead prices across Central and Southeast Europe are already showing premiums linked to the pressure at Paks and Cernavodă (Serbia Energy).

The first losers are Nuclearelectrica's customers. The company has warned them it may not meet delivery contracts and is claiming force majeure, the legal defence used when an extraordinary external event prevents a company from fulfilling its obligations (ZF).

Industrial users are next in line. They face voluntary or mandated demand cuts before households see any retail-price change. Transelectrica, Romania's grid operator, has 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). That is useful as far as it goes. Europe's electricity market is built to move power to where it is needed most. The weakness exposed by this drought is more basic: Romania, Hungary and Bulgaria all need extra electricity in the same evening hours, and the river cooling their plants is the same river running out of water.