Slovakia's new 471 megawatt (MW) Mochovce Unit 3 nuclear power plant over the weekend took another step towards being ready to launch in early 2023, reaching a sustained chain reaction state, utility Slovenske Elektrarne said on its website.

The unit will produce around 3.7 Terrawatt hours per year, covering 13% of Slovakia's electricity consumption and making the country self-sufficient, the company co-owned by the Slovak government, Italy's Enel and Czech energy group EPH, has said.

"Controlled fission chain reaction is already under way in the reactor, although the reactor power is very close to zero," Slovenske's Director General Branislav Strycek said in the website statement.

He added the reactor should be at full power in early 2023.

Mochovce is based on the originally Soviet VVER design with control systems from Siemens and Areva.

Once Mochovce Unit 4 is complete, around two years after Unit 3 is functioning, Slovakia is expected to become a net electricity exporter to other European Union countries. (Reporting by Jan Lopatka; editing by Barbara Lewis)