Europe’s newest reactor prepares to start up after 39-year wait

Almost four decades after the fall of communism in Slovakia, a Soviet-designed reactor is finally about to produce power.

Fuel loading began at the fourth and final unit of the Mochovce nuclear plant on Monday, paving the way for commercial startup by the end of the summer. It’ll also be the fourth new reactor commissioned in the European Union in three years, underscoring the bloc’s efforts to bolster clean power just as widespread electrification and a burgeoning data-center buildout boost demand.

Completing the facility was far from easy. At 39 years, it’s the second-longest construction time in the industry’s history, reflecting difficulties with funding, changing safety regulations and faulty workmanship. The project also does nothing to reduce the EU’s reliance on Russian energy, with Mochovce’s nuclear fuel supplied solely by Rosatom’s TVEL Fuel Co. — at least for now.

The new plant will “ensure we have a reliable energy supply at all times,” said Branislav Strycek, chief executive officer of Slovenske Elektrarne, the utility controlled by Czech billionaire Daniel Kretinsky that operates the complex. “This is a significant step forward for Slovakia and for the wider eastern European region.”

Several countries in Europe are adding reactors in a bid to strengthen energy security without burning fossil fuels and jeopardizing climate goals. While renewables are also expanding at a rapid clip, nuclear plants can provide round-the-clock power, running regardless of weather conditions to stabilise the grid.

The new reactor at Mochovce will come online just a few years after another unit at the sprawling site was connected to the network. France and Finland have also added atomic stations since 2023.

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Russian dominance

Despite efforts to curb reliance on fossil-fuel imports — including an EU phaseout of Russian gas by the end of next year — Moscow’s grip on nuclear-fuel supplies persists. Indeed, Slovenske Elektrarne has stockpiled enough from TVEL to supply its six reactors until 2031.

Yet the utility is also looking to diversify, working with both Westinghouse Electric Co. and France’s Framatome on future supplies. The first deliveries from both companies are expected in 2028, although Framatome’s fuel will initially be produced by a Franco-Russian joint venture and will only become fully European within about a decade.

Russia accounts for an estimated 40% of the world’s uranium enrichment capacity. Slovakia has objected to European Commission proposals for a swift wind-down of Russian nuclear-fuel imports, arguing that alternative global suppliers don’t yet have sufficient capacity to meet demand.

The EU does have its own enrichment capability. If the bloc were to stop other countries from using it, Slovenske Elektrarne could in theory cut out Russian fuel by 2032, Strycek said in an interview on Friday.

Nuclear’s swellingshare

The new VVER-440 reactor at Mochovce is expected to generate about 3.5 terawatt-hours of electricity a year, boosting nuclear’s share of Slovakia’s total power generation to 77%, according to Strycek.

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Work on the final two reactors at Mochovce began in 1987, but was halted in the early 1990s when the centrally planned economy collapsed following the fall of communism.

It was Prime Minister Robert Fico who in 2008 pushed Italy’s Enel SpA — Slovenske Elektrarne’s owner at the time — to resume construction. It was expected to be completed in five years at a cost of about €2.8 billion ($3.2 billion), but the price tag ultimately ballooned to €6.7 billion.

Only America’s Watts Bar nuclear plant in Tennessee took longer to build, with construction lasting 43 years.

Beyond Mochovce, the Slovak government has plans for another reactor at Jaslovske Bohunice in the west of the country, in cooperation with Westinghouse. The project remains at an early stage, with completion not expected until around 2040.

Slovakia is already self-sufficient in electricity production, meaning all new capacity is expected to be exported.

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