The loading of the fuel into the new reactor in Slovakia marks the transition from the construction phase to the start-up phase of a new nuclear power unit.
The VVER-440 unit will now move on to pre-criticality tests before the first controlled fission reaction takes place, all under the supervision of the Slovak Republic’s Nuclear Regulatory Authority.
There will then be a series of tests to verify the properties of the reactor core before the unit’s output is increased in small steps, with tests taking place at each stage before regulators clear an increase in power levels.
The 349 assemblies in the reactor are 312 fuel assemblies and 37 control assemblies. The fuel is uranium dioxide in the form of ceramic tablets, which each weigh about 5 grams and are in fuel rods. One fuel assembly includes 126 fuel rods. When fully loaded, the reactor contains about 42 tonnes of nuclear fuel, and fuel assemblies remain in the core for about five years, Slovenské elektrárne said.
Martin Mráz, Project Director Mochovec, Slovenské elektrárne, said: “The completion of fuel loading into unit 4 is another significant step on the way to completing the Mochovce project. With this unit, we are closing one of the most important chapters in the Slovak energy sector. The result will be a stable and reliable source of low-emission electricity for households, industry and future generations. It is the success of thousands of people who have been involved in the project for many years.”
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 (SPH), 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.
