Two weeks after the 349 fuel assemblies were loaded, a series of checks and tests have taken place to confirm the readiness of the primary circuit for the next stage of start-up of the VVER-440 unit.
Slovenské elektrárne is aiming for unit 4 to deliver the first electricity to the grid after the turbogenerator is phased in at the end of summer 2026. It will then have its power gradually increased – with tests and checks at each level – before a final 144-hour test at full power.
Martin Mráz, director of the MO34 project, said: “By completing the assembly of the reactor, we have concluded one of the key stages of physical start-up. Ahead of us are strength and leak tests, pre-critical tests and then the first criticality, ie the first controlled fission chain reaction.”
Branislav Strýček, Chairman and CEO of Slovenske elektrárne, said: “Mochovce has once again come close to its goal. In recent days, we have successfully completed two key operations – the loading of nuclear fuel and the assembly of the reactor.”
He said they were now entering the start-up phase and “each of these milestones brings us closer to the moment when Slovakia will fully utilise the potential of the completed Mochovce and the new unit will begin generating electricity for households and businesses for decades to come”.
Background
Construction of the first two VVER-440 units at the four-unit Mochovce plant started in 1982. Work began on units 3 and 4 in 1986, but stalled in 1992. The first two reactors were completed and came into operation in 1998 and 1999, respectively, with a project to complete units 3 and 4 beginning ten years later at an estimated cost of EUR6.7 billion (USD7.6 billion).
Mochovce 3 entered commercial operation in October 2023. Each of the units can provide 13% of Slovakia’s electricity needs when operating at full capacity and when the 471 MW-capacity unit 4 is operating, nuclear will be providing the equivalent of 77.5% of Slovakia’s electricity consumption, the highest proportion for any country.
Slovenské elektrárne’s majority shareholder is Slovak Power Holding BV (SPH), which is owned by the Czech energy group Energetický a průmyslový. The second shareholder is the Slovak Republic, which has a 34% stake.
Slovakia currently has five nuclear reactors generating about half its electricity. As well as the Mochovce units, there are two at Bohunice, which went into commercial operation in 1984 and 1985, respectively. The Slovak government has plans for a new large unit at Bohunice, and has also been exploring the potential for small modular reactors in the country.
