Hungary’s Paks Nuclear Power Plant has successfully restarted its sixth turbine, with the unit now generating electricity again as the country’s largest power plant moves faster than expected towards full capacity.

Prime Minister Péter Magyar announced late on Saturday that the sixth turbine of Unit 3 had reached its target speed of 3,000 revolutions per minute and had begun producing electricity again. The restart means that three of the plant’s eight turbines are now operating, with further units expected to come back online on Sunday morning.

Magyar said the plant could return to its full output of 2,000 megawatts by Wednesday, following emergency works to raise and stabilise the Danube’s water level.

Third turbine successfully restarted

Magyar announced on Saturday evening that engineers had begun reconnecting the sixth turbine of Unit 3, which had been offline because of the exceptionally low water level of the Danube.

By around midnight, the turbine had reached 3,000 rpm and resumed electricity generation.

The prime minister said the turbine would now contribute electricity to Hungarian households and businesses, while additional turbines were expected to restart by Sunday morning. The latest development are a significant improvement from earlier this month, when only two turbines were operating at Paks.

Why does restarting a turbine take 49 hours?

Although the final stage of the restart attracted considerable attention on Saturday night, the process had actually begun almost two days earlier. According to Károly Vigh, the plant’s director of operations, restarting a turbine takes around 49 hours.

During the process, the turbine is initially kept turning at just 3–4 revolutions per minute. This is necessary to prevent the turbine shaft from bending as it is exposed to steam and to ensure that heat is distributed evenly.

The turbine is then brought up to speed in stages. First, its speed is increased to 600 rpm, followed by a technical inspection. It is then raised to 900 rpm and checked again before the final acceleration to 3,000 rpm.

The last stage is the most critical, with the turbine’s speed increased by 600 rpm at a time. Once the target speed is reached, a further 90 minutes to two hours may be required before the turbine’s electricity generation appears on the MAVIR transmission network.

For Paks engineers, the procedure itself is not unfamiliar. The plant carries out between six and ten planned turbine restarts every year as part of maintenance and repair work.

If you missed it: Paks nuclear plant begins turbine restart as Hungary races towards full capacity

Paks restart moving faster than expected

The latest progress is also ahead of the timetable previously announced by the government. Magyar said on Sunday morning that construction of the bottom sill in the Danube was progressing faster than expected and that four of Paks’s eight turbines were already generating electricity.

The prime minister said the gradual restoration of the plant’s capacity was continuing and that Paks could return to its full 2,000 MW output by Wednesday. At full capacity, the plant is expected to cover around 35 per cent of Hungary’s electricity consumption, according to Magyar.

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Emergency Danube works remain crucial

The rapid restart has been made possible by a combination of rising water levels and emergency construction works on the Danube. Paks was forced to reduce its output after the river reached exceptionally low levels during the summer heatwave. The plant requires sufficient river water for cooling, and the situation became serious enough in late July to force Unit 3 to shut down.

The government subsequently ordered the construction of a bottom sill in the Danube near the plant to raise the water level at its cooling-water intake. Temporary barges were also deployed in the riverbed, while other measures were taken to increase the amount of water available to the plant.

The works have already raised the water level around Paks, allowing the restart process to proceed sooner than originally expected.