Slovakia has entered the final stage of expanding the Mochovce Nuclear Power Plant after operators began loading nuclear fuel into the facility’s fourth reactor, a milestone that will further increase the country’s reliance on nuclear energy.
The state-owned nuclear regulator, the Nuclear Regulatory Authority, approved the reactor’s commissioning last week, clearing the way for Slovenske elektrarne to start fuel loading on June 29. The move marks the beginning of a testing programme that will continue for several months before the reactor enters permanent commercial operation.
The utility expects the new unit to reach full capacity by the end of the year, following a gradual increase in output and a series of mandatory safety and performance tests.
Once the reactor is fully operational, nuclear power will account for about 77% of Slovakia’s electricity production.
The fourth reactor is the last unit to be completed at Mochovce, bringing to an end an expansion project that has dominated Slovakia’s energy sector for years. The neighbouring third reactor started commercial operation in 2023 after an extended commissioning process.
Although fuel loading represents a major technical step, electricity generation will begin only after regulators approve successive testing phases. These include operating the reactor at different power levels before it undergoes a continuous 144-hour test at full output, a standard requirement before commercial operation.
According to Nuclear Regulatory Authority chair Marta Ziakova, the experience gained during the commissioning of the third reactor should make the process smoother this time. She said the reactor is expected to operate at around 20% of its capacity by the end of August, before gradually increasing production, Index wrote.
The new reactor has an installed capacity of 471 megawatts and is expected to generate 3.5-4 terawatt-hours of electricity annually. According to Slovenske elektrarne, that would cover roughly 13% of Slovakia’s electricity demand.
The additional capacity is expected to reinforce Slovakia’s position as a net electricity exporter. Nuclear energy already forms the backbone of the country’s power system, with Slovenske elektrarne producing most of its electricity from its nuclear plants in Mochovce and Jaslovske Bohunice.
The completion of Mochovce’s final two reactors comes after years of construction delays and rising costs. Both units were originally expected to enter operation much earlier, with the fourth reactor initially scheduled for completion in 2014. The project ultimately slipped by more than a decade.
Construction costs also increased substantially. While the expansion was initially budgeted at less than EUR 2.8 billion, current estimates put the total cost at around EUR 6.7 billion.
The prolonged construction placed considerable financial pressure on Slovenske elektrarne, which relied on repeated capital injections from its shareholders after commercial banks became reluctant to provide additional financing, according to Index. The company has since recovered, reporting record profits last year.
Ownership of Slovakia’s largest electricity producer has also changed during the project’s final stages. Slovak Power Holding, controlled by Czech energy group EPH, owns a majority stake, while the government retains a 34% share after Italian utility Enel completed its exit from the company last year. (The Slovak Spectator)