Slovakia connects Mochovce 4 nuclear unit to grid after brief delay

Slovak technicians have successfully connected a new nuclear unit at the Mochovce power plant to the electricity grid. The unit has begun supplying its first MWh of electricity. Before entering commercial operation, the 471 MW unit will undergo tests at various power levels. Once fully operational, the installed capacity of Slovakia’s nuclear units will exceed 2.75 GW. 

Slovenské elektrárne announced that it connected the new nuclear unit at the Mochovce power plant to the electricity grid for the first time on the evening of Thursday, 15 October. The connection had originally been scheduled for Tuesday, 13 October, but the company postponed it by two days because the unit had to repeat a technical test. Technicians synchronised the new VVER-440 unit, with an installed capacity of 471 MW, with the grid at 20% power.

“For the first time in history, Unit 4 of the Mochovce power plant is supplying electricity to the Slovak power system. This is a moment generations of people who prepared, built and commissioned this project have been waiting for. Today, we see the result of their work in the form of a new low-emissions source of electricity for Slovakia,” said Branislav Strýček, chairman of the board and CEO of Slovenské elektrárne .

The company said that the process, which lasted barely a few seconds and saw the first of the two turbogenerators connected to the grid, was preceded by years of preparation. The unit will now gradually increase its output, the second turbogenerator will be connected to the grid, and the performance of its technological, control and safety systems will be verified. After successfully completing a test at full power, the unit will enter commercial operation.

“In the unit control room, operators control the reactor’s output and monitor the operation of the steam generators, turbine and generators. Electricians then establish a safe connection to the grid. Today’s moment was brief, but it was made possible only by the perfectly coordinated work of many different specialists,” said Martin Mráz, project director for Mochovce 3 and 4.

The path to six nuclear units

Slovakia has two nuclear power plants—Jaslovské Bohunice and Mochovce. The former has two operating VVER-440 reactors; the first two VVER-440 units at the site stopped supplying electricity in 2006 and 2008.

Construction of four VVER-440 units at the Mochovce power plant began in the 1980s. However, only two were completed before 2000. The second pair had to wait more than 20 years to come online. Slovakia brought the Mochovce 3 nuclear unit online in 2023. With Mochovce 4, Slovakia’s nuclear capacity will exceed 2.75 GW, and the country will achieve a very high share of nuclear generation in its electricity consumption.