Cold hydro testing under way at Slovakia's Mochovce 4

Thursday, 2 January 2025

The cold hydro-testing of unit 4 began in early December, Slovenské elektrárne has said. Cold functional tests are carried out to confirm whether components and systems important to safety are properly installed and ready to operate in a cold condition. The main purpose of these tests is to verify the leak-tightness of the primary circuit and components - such as pressure vessels, pipelines and valves of both the nuclear and conventional islands.

Peter Andraško, deputy director of the Mochovce unit 4 project, said: "Following the successful completion of the inactive functional tests, we are entering the second phase of the inactive tests of the plant commissioning process. These are the so-called staged inactive testing programmes. The first of them is the cold hydrotest of the primary circuit."

Martin Mráz, director of completion and commissioning of systems at Mochovce unit 4, said: "A small revision, a hot hydro test and a large revision will follow, which will end the inactive tests. Once the fuel loading application is approved by the Nuclear Regulatory Authority of the Slovak Republic, we will load nuclear fuel into the reactor and start active tests."

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.