Low Danube Threatens Romanian Power

At Cernavoda, on Romania's lower Danube, the river is running at roughly 1,600 cubic metres per second, less than 40% of its normal July flow (Digi24, Bloomberg). For a nuclear plant, that is not just a worrying hydrological statistic. It goes to the basic mechanics of how the plant stays alive.

A reactor makes electricity by producing heat. The surplus heat has to go somewhere, and at Cernavoda it is carried away by river water pumped through cooling systems. If the Danube falls too far, those pumps can no longer be used safely. The reactor comes off the grid, and a steady source of low-carbon electricity, the kind that does not care whether the wind is blowing or the sun is shining, simply vanishes.

Romania declared a national energy alert for August on 31 July. This is an energy-system measure, not a constitutional emergency (Mediafax). Interim prime minister Ilie Bolojan said drought could put roughly 20% of national electricity output at risk (RRI, Agerpres). The hardest hours come between 20:00 and 23:00, when solar power fades but households are still cooking, cooling rooms and running appliances.

The same problem is moving along the river system. Hungary's Paks plant has cut output by half. Bulgaria's Kozloduy is under special monitoring. As we reported last week (To Brief), the heatwave had already forced Cernavoda's Unit 1 offline. Since then, the pressure has only grown.

Sinking barges to save a reactor

Cernavoda's Unit 1 was disconnected on 28 July. The Energy Ministry warned that pushing cooling pumps at such low flows could damage equipment and require repairs lasting up to a year (Agerpres). Unit 2 went through an overnight review on 30 July and remained connected, but only under strict monitoring (Curs de Guvernare, Romania Insider).

To keep that last reactor running, Bolojan allocated 7 million lei from the government reserve for emergency works at a river junction upstream. The aim is to push more flow towards Cernavoda's intake basin. Officials discussed sinking metal barges to steer the main current towards the plant (Adevarul, Digi24). Romania is, in effect, physically reshaping a stretch of the Danube to keep one nuclear reactor on the system.

Same river, same squeeze

Hungary is in a tighter spot. The Danube gauge at Paks hit -122 cm on 30 July, a record low (kormany.hu). By 31 July, one unit was shut and another was running at half power, leaving output at roughly half the plant's capacity. The plant operator MVM warned that a full shutdown could become unavoidable within days (MVM Paks, HVG).

Bulgaria's Kozloduy, also cooled by the Danube, was still operating but had activated procedures for low-river conditions. Energy Minister Iva Petrova contacted Serbia about managing flows through the Iron Gate dam complex upstream (24 Chasa). Austria's largest hydro producer, Verbund, separately reported that drought had cut its output to 68% of plan (Kleine Zeitung). The same dry spell is weakening nuclear and hydro generation together.

Who pays when cheap power disappears

When nuclear output falls, the missing power has to be replaced by something dearer. Romania expected peak demand of around 7,300 MW, while domestic production was only 4,000-4,300 MW. By evening it was already importing about 1,700 MW, mainly from Bulgaria (Profit.ro, EUAlive). A country that had been an exporter of power had become an importer.

The winners are gas plants and battery operators, which can sell into the expensive scarcity hours. Nuclear operators lose revenue. Suppliers that have promised households fixed prices must buy replacement electricity on the wholesale market. Analysts at Hungary's Portfolio estimated that replacing Paks output through imports could widen Hungary's trade gap, the difference between what the country pays abroad for energy and what it earns from exports, by up to 1% of GDP (Portfolio). Bolojan asked Romanian households to run washing machines and boilers after 23:00 (Mediafax).

The immediate risk is not blackouts. The problem is that several countries are losing cheap power at the same time, then turning to neighbours dealing with the same river. Forecasts show flows falling further towards 1,500 m³/s at Cernavoda and -130 cm at Paks by 3 August (RRI, kormany.hu). Emergency barges and shifting household demand buy days, not weeks. Summer drought can now take reliable low-carbon power out of several connected electricity markets at once. Europe's grid planning has not caught up with that fact.