€15 Million Lifts Paks by 20cm

Crews on the Danube sank two barges and built a temporary dam on the riverbed to lift the water level by a matter of centimetres. It was enough. By 23 August, Hungary's only nuclear plant had four of its eight turbines back online, output above 800 MW, and the government was saying full 2,000 MW capacity should return by midweek (Portfolio, Euronews HU). The case matters well beyond Hungary because Romania tried a similar emergency operation at Cernavodă, its own sole nuclear plant, and still lost both reactors. Emergency engineering can recover the margin a pump needs. It cannot command a river to stop falling.

What crews built and why it was enough

Nuclear plants need vast amounts of water to cool the steam after it has driven the turbines. At full power, Paks needs around 100 cubic metres per second of Danube water. When the river fell to record lows, the plant's fixed-depth pumps could no longer draw enough water, and operator MVM began reducing output in late July (MVM).

On 12 August, the government ordered two interventions. The first was a bottom sill: a low barrier on the riverbed that slows the current and backs water up towards the intake. The second was the controlled sinking of two 80-metre barges to block more of the flow. The bill was HUF 6.1 billion, about €15 million, against an official estimate of at least HUF 50 billion per month to replace the power lost in a full shutdown (kormany.hu, Energy Connects). Spending €15 million to avoid €50 million a month in losses is the kind of calculation even a finance ministry can make quickly.

By 22 August, crews had built 242 metres of sill. Together with the sunken barges, it raised the water level by more than 20 cm. Seven of the eight cooling pumps were operating and the intake was close to capacity (kormany.hu, MTI).

Romania's warning

Romania had already tried much the same approach at Cernavodă, which normally provides about a fifth of the country's electricity (World Nuclear). Crews blasted a rock formation, dredged channels and sank barges to redirect Danube water towards the intake (The Guardian, Financial Intelligence). The first intervention lifted the water by 8 cm and gave Unit 2 roughly nine more days (HotNews). Then the Danube kept dropping. Unit 2 shut down on 13 August. Romania has since approved a second emergency package because the first operation bought time, not security (AGERPRES).

The difference was not competence. Both countries spent money and moved fast against the same physical constraint. Hungary's works produced 20 cm where 20 cm was enough. Romania's produced 8 cm while the shortfall continued to widen.

Who paid, who profited

As Paks moved towards shutdown, Hungarian week-ahead power climbed to around EUR 250–263/MWh, about 15–20% above the previous day's level (Argus). Those prices reach industrial buyers quickly. Hungary doubled electricity imports, reaching around 4 GW at night, while the government asked households not to use washing machines and dryers between 17:00 and 22:00 (Euractiv). A separate decree allowed the grid operator to cut large industrial consumers above 0.5 MW, with penalties set at 200% of the spot price for those who ignored the order (HVG). Households were asked to cooperate. Factories were compelled.

Romania's exposure was more abrupt. On one evening, imports reached 1,839 MW, covering 27.4% of consumption (Curs de Guvernare). Bulgaria was the immediate winner, with exports rising to roughly 32,000–33,000 MWh per day as nuclear output vanished next door (Mediapool). Slovakia, whose Mochovce and Bohunice plants use cooling towers rather than direct river cooling, kept producing at full power and benefited from higher regional prices (Info.sk).

The river still decides

Hungary avoided the immediate cost of replacing Paks. The sill-and-barge operation cost €15 million, while the losses from a full shutdown would have run into tens of millions each month. For any small EU economy, Malta included, the lesson is familiar: infrastructure that looks like a national asset in ordinary weather becomes a national vulnerability when the operating assumptions change.

The restart does not remove that vulnerability. Paks still depends on Danube water reaching fixed-depth pumps, and the next low-water spell may be longer or deeper than a temporary sill can handle. France's EDF is spending €9 billion over 15 years to climate-proof its nuclear fleet (Le Monde). Hungary built 242 metres of sill in eleven days. The real test is whether that still buys enough water next August.