€15 Million Buys Paks 20 Centimetres

Crews sank two barges and built a temporary dam on the Danube riverbed to raise the water level by centimetres. It worked. By 23 August, Hungary's only nuclear plant had four of its eight turbines running, output above 800 MW, and the government expects full 2,000 MW capacity by midweek (Portfolio, Euronews HU). The restart matters because Romania tried comparable emergency works at Cernavodă, its sole nuclear plant, and still lost both reactors. Emergency engineering can restore a pump margin. It cannot stop a falling river.

What crews built and why it was enough

Nuclear plants use huge volumes of river water to cool steam after it drives the turbines. Paks needs roughly 100 cubic metres per second of Danube water at full power. When the river dropped to record lows, the plant's fixed-depth pumps could no longer draw enough (MVM). Operator MVM began cutting output in late July.

On 12 August, the government ordered two fixes. First, a bottom sill: a low structure on the riverbed that slows the current and backs water up at the intake. Second, two 80-metre barges prepared for controlled sinking to block more flow. The cost was HUF 6.1 billion (about €15 million), set against an official estimate of at least HUF 50 billion per month in replacement power from a full shutdown (kormany.hu, Energy Connects). Fifteen million euros to avoid fifty million per month is not a hard decision.

By 22 August, 242 metres of sill had been built and the combined effect raised the water level by more than 20 cm. Seven of eight cooling pumps were running and intake was close to capacity (kormany.hu, MTI).

Romania's warning

Romania tried the same playbook at Cernavodă, which normally supplies about a fifth of its electricity (World Nuclear). Crews blasted a rock formation, dredged channels, and sank barges to redirect Danube flow toward the intake (The Guardian, Financial Intelligence). The first intervention raised the water by 8 cm and bought Unit 2 about nine extra days (HotNews). Then the river kept falling. Unit 2 shut on 13 August. Romania has since approved a second emergency package because the first bought time, not security (AGERPRES).

The difference is not engineering skill. Both countries threw resources at the same problem. Hungary's sill delivered 20 cm where 20 cm was enough. Romania's interventions delivered 8 cm where the deficit kept growing.

Who paid, who profited

When Paks moved toward shutdown, Hungarian week-ahead power jumped to around EUR 250–263/MWh, roughly 15–20% above the previous day's level (Argus). Those prices flow through to industrial buyers within days. Hungary doubled electricity imports, reaching about 4 GW at night, and the government asked households to avoid washing machines and dryers between 17:00 and 22:00 (Euractiv). A separate decree gave the grid operator authority to cut large industrial consumers above 0.5 MW, with penalties at 200% of the spot price — factories that ignored the order paid double the market rate (HVG). Households were asked; factories were ordered.

Romania's exposure was sharper. One evening, imports hit 1,839 MW, covering 27.4% of consumption (Curs de Guvernare). Bulgaria became the short-term winner: its exports surged to roughly 32,000–33,000 MWh per day as neighbouring nuclear output disappeared (Mediapool). Slovakia, whose Mochovce and Bohunice plants use cooling towers instead of river water, kept running at full power and quietly collected higher regional prices (Info.sk).

The river still decides

Hungary avoided the immediate cost of replacing Paks. The sill-and-barge fix cost €15 million against losses that would have run to tens of millions per month. But the restart does not remove the exposure. Paks still draws cooling water from the Danube through fixed-depth pumps, and the next low-water episode may last longer than a sill can manage. 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 question is whether that will still be enough next August.