Hot hydro testing begins at Mochovce 4

Monday, 24 March 2025

The purpose of the testing is to perform pressure and leak checks of the primary circuit and reactor, functional tests of the primary and secondary circuit equipment, safety systems, air conditioning, electrical components and control and management systems.

Slovenske elektrárne Chairman and CEO Branislav Strýček said: "The project to complete unit 4 in Mochovce has achieved significant milestones - a cold hydro test and a small revision. With the hot hydro test, we are in the next stage of the inactive testing programme. Our goal is to load fuel into the reactor this year after all necessary tests and revisions have been completed, so that we can generate even more electricity in Slovakia reliably and without direct CO2 emissions."

The company said that "during the cold hydro test, the primary circuit was heated to 130°C and pressurised to 13.7 MPa, which is more than 111% of the operating pressure".

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.

Mochovce 3 entered commercial operation in October 2023 and unit 4's schedule has been to follow about two years behind unit 3. Each of the units will be able to provide 13% of Slovakia's electricity needs when operating at full capacity.