Power start-up for Mochovce 4

The unit reached critical status and minimum controlled power at the start of August. The Slovak Republic's Nuclear Regulatory Authority performed inspections and assessed documentation before giving the go-ahead for the latest stage of commissioning.

The switch from the physical to energy launch means that heat from the reactor will heat water to produce the steam to spin the turbines.

The reactor's power output will now be gradually increased in stages - 5%, 20%, 35%, 55%, 75% and 90% - with checks and tests at each level before being increased. It will be phased into Slovakia's electricity system when it reaches 20%.

The final test will be a 144-hour run at 100% power.

Branislav Strýček , Chairman and CEO of Slovenske elektrárne, said: "After the successful completion of this phase, Slovakia will gain a new stable source of electricity that will contribute to the country's energy security and the achievement of its climate goals for decades."

Martin Mráz, project director of the Mochovce completion project, said: "We have successfully completed the fuel loading and physical start-up stages … the milestone achieved is confirmation of the high professional level of the Slovenské elektrárne project team and the quality of work of everyone who participated in the completion."

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, 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.