Danube Drop Threatens Romanian Power

At Cernavoda, on Romania's lower Danube, the river is carrying about 1,600 cubic metres of water a second. That is less than 40% of its normal July flow (Digi24, Bloomberg). For a nuclear plant, this is not a picturesque drought story. Reactors generate electricity by producing heat, and the heat left over has to be carried away by river water pumped through cooling systems. If the river falls too far, the pumps cannot operate safely. The reactor is taken off the grid, and a source of steady low-carbon electricity, the kind that does not depend on whether the wind is blowing or the sun is out, disappears.

Romania declared a national energy alert for August on 31 July. This is an energy-system alert, not a constitutional emergency (Mediafax). Interim prime minister Ilie Bolojan said drought could put around 20% of national electricity output at risk (RRI, Agerpres). The most exposed hours are between 20:00 and 23:00, when solar production drops but families are still cooking, cooling homes and using appliances.

The same pressure is showing up along the river. 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 problem has moved from a plant outage to a regional energy risk.

Sinking barges to save a reactor

Cernavoda's Unit 1 was disconnected on 28 July. Romania's Energy Ministry warned that pushing the cooling pumps at such low flows could damage them badly enough to 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 on the grid, Bolojan released 7 million lei from the government reserve for emergency works at a river junction upstream. The aim is to push more water towards Cernavoda's intake basin. Officials have discussed sinking metal barges to redirect the main current towards the plant (Adevarul, Digi24). Romania is, in effect, reshaping part of the Danube to keep one nuclear reactor running.

Same river, same squeeze

Hungary is in an even tighter position. The Danube gauge at Paks reached -122 cm on 30 July, a record low (kormany.hu). By 31 July, one unit had been shut and another was running at half power, leaving the plant at roughly half its capacity. Operator MVM warned that a full shutdown could become unavoidable within days (MVM Paks, HVG).

Bulgaria's Kozloduy plant, which also depends on Danube cooling water, 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 hydropower producer, Verbund, separately reported that drought had cut its output to 68% of plan (Kleine Zeitung). Low water is hitting nuclear and hydro at the same time.

Who pays when cheap power disappears

When nuclear output falls, more expensive power replaces it. Romania expected peak demand of about 7,300 MW, while domestic production was only 4,000–4,300 MW. By evening it was already importing around 1,700 MW, mainly from Bulgaria (Profit.ro, EUAlive). Romania has moved from exporter to importer.

Gas plants and battery operators benefit because they can sell during the expensive evening hours. Nuclear operators lose revenue. Suppliers with fixed-price household contracts have to buy dearer replacement electricity on the wholesale market. Analysts at Hungary's Portfolio estimated that replacing Paks output through imports could widen Hungary's trade gap, meaning 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 risk is not that the lights go out immediately. It is that several countries lose cheap power at the same time and then turn to neighbours facing the same river constraint. 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 into the night can buy days, not weeks. The Danube is showing a harder lesson for Europe's grid planners: summer drought can take out reliable low-carbon power across connected electricity markets at the same time.