Mochovce Nuclear Power Plant

Mochovce NPP consisting of four pressurised water reactors WWER 440/V-213 is located in the geographic centre of Europe – in the south Slovakia, between the historic towns of Nitra and Levice.

The Unit 1 has supplied electricity to the grid since the summer of 1998, Unit 2 since late 1999. In 2008, gross power output of each unit was uprated from 440 to 470 MW by 7% increase of the reactor power, and in 2020, the Unit 2 electrical output was uprated again to 505 MWe by replacement and modification of the secondary circuit components. The same electrical output uprate of the Unit 1 is planned in the spring of 2021.

The two operating Mochovce units deliver roughly 7 million MWh of electricity annually that equals to more than a quarter of Slovakia's electricity demand, thus preventing over 7 mil. tonnes of CO2 emissions every year as compared to a typical coal-fired power plant.

Construction of the Units 3 & 4 is in the final stage  - the Unit 3 shall be commissioned in 2021, and the Unit 4 will follow two years later.

20000BC: Inhabited by humans, stone axe found 20 000 BC
Inhabited by humans, stone axe found
1 259 AD
First written mention of a settlement called Mohi
1 259 AD: First written mention of a settlement called Mohi
1 981: Start of construction works at Mochovce – ground works 1 981
Start of construction works
at Mochovce NPP – ground works
Start of construction works on Mochovce NPP unit 1 and 2
Start of construction works on Mochovce NPP unit 3 and 4
Replacement of the instrumentation and control system
Halt of the construction works
Re-start of conrtruction works on unit 1 and 2
Commissioning of Mochovce NPP unit 1 and 2 1998
Commissioning of unit 1

Commissioning of unit 2
Enel acquired 66 % of Slovenské elektrárne
Unit 1 and 2 installed output increased to 107%
Start of the Mochovce NPP 3&4 completion project
Unit 2 installed output increased to 505 MWe
Green field
Green field
Number of units 2
Reactor type VVER 440/V 213 - tlakovodný
Reactor heat capacity 1 471 MWt
Reactor rated output* 470/505 MWe
Self-consumption* 35 MW (7 % of the rated output)
Unit efficiency* 34%
Reactor pressure vessel
- internal diameter 3 542 mm
- wall thickness 140 + 9 mm
- height 11 805 mm
- weight (less internals) 215 150 kg
- material Cr-Mo-V steel
Primary circuit
- number of cooling loops 6
- coolant flow rate 42 600 m3/h
- operating pressure 12,26 MPa
- reactor output coolant temperature 297,3 °C
- reactor input coolant temperature 267,9 °C
- core temperature drop 29°C
- overall volume 242 m3
- number of operating fuel assemblies 312
- number of control fuel assemblies 37
- total fuel assemblies 349
- core fuel weight 42 t
- fuel used UO2
- medium fuel enrichment 4,87 % U235
Steam-generator 6 per unit
- PG type V-213
- amount of steam generated 450 t/h
- steam output pressure 4,61 MPa
- steam output temperature 255 °C
- feed water temperature 222 °C
- weight 169 t (less suspensions)
Conventional island
Turbo-generator 2 per unit
- Type ŠKODA - K 250-44 250 MWe
- number of stages 1 high-pressure, 2 low-pressure
- rated rotational speed 3 000 rpm
- generator rated apparent output* 277 MVA
- terminal voltage 15,75 kV
- rated current 3 x 10130 A
- amount of cooling water 35 000 m3/h
- maximum cooling water temperature 33 °C
Cooling towers  
Number of towers 4
Height 125 m
Bottom diameter  
Upper diameter  
Pool diameter  
Emergency systems
4 hydro-accumulators 70 m3 each
of which:  
- water volume 40-50 m3
- nitrogen volume 20-30 m3
barbotage tower  
- overall barbotage well capacity 13 800 m3
- 4 capture chambers for gases with a capacity 16 140 m3
- 12 barbotage throughs 1 380 m3
high-pressure system  
- pump capacity 65 m3/h
- outlet pressure 13,5 MPa
low-pressure system  
- pump capacity 800 m3/h
- outlet pressure 0,72 MPa
- pump capacity 380-520 m3/h

* data for Mochovce 2 after turbine replacement and power increase

Nuclear power plants in Slovakia emit no greenhouse gas to the atmosphere during operation, except for water aerosol released from cooling towers, hence contributing to annual CO2 emission reduction by 15 million tonnes.

Nuclear power plants thus contribute significantly to the obligation of reducing the emissions of greenhouse gases to the atmosphere and carbon neutrality by 2050. Slovenske elektrarne supplied 92.5% of electricity from low-carbon sources in 2019, and the figure will even increase after commissioning of the Mochovce NPP Units 3&4.

Mochovce NPP meets all national and international environmental requirements and its operation environmental impact is minimal. Water needed for cooling is taken from a water dam on the nearby Hron river, which has sufficient flowrate even in extremely dry months. Impact of effluents discharged from the power plant site on the Hron river water quality, fauna and flora is practically negligible.

Atmospheric emissions and hydrosphere effluents are regularly measured and evaluated in the 15-km area around the plant. There are 40 monitoring stations (19 on site and 21 off-site) of a tele-dosimetry system, which continuously monitor dose rate of gamma radiation, volume activity of aerosols and radioactive iodine in the air. Moreover, samples of soil, ground water and food chain (feed, milk, agricultural products) are regularly analysed, too. The volume of radioactive substances contained in liquid and gaseous discharges is considerably lower than the limits set out by authorities. Monthly reports of releases into environment are available in the section Publications.

In addition to common communal wastes, operation of nuclear power plants also produces a small amount of radioactive wastes. One unit annually produces approx. 13 m3 of liquid and 15 tonnes of solid low-level radioactive wastes. Such wastes need to be treated and safely disposed of, so that they were isolated from the environment. Liquid radioactive wastes are treated right at Mochovce, solid radioactive wastes at Bohunice treatment centre. Compacted wastes in fibre-concrete containers are then transported and stored at the National radioactive waste repository at Mochovce. Treatment and disposal of radioactive wastes is a capacity of the state-owned company JAVYS.

Every year during a general outage, one fifth of the fuel is replaced in the reactor (i.e. 66-72 of 349 fuel rods), that is around 8 tonnes of uranium. Spent fuel rods are cooled down for 5 to 6 years in a pool next the reactor and then they are transported into the interim spent fuel storage at Jaslovske Bohunice, which is operated by JAVYS. The spent fuel is stored in water pools there. Water provides excellent shielding preventing the leak of radioactivity into environment. Further energy use of the spent fuel is assumed in the future using new technologies.

Občianska informačná komisia Mochovce

Civic Information Committee (CIC) of Mochovce is an independent information channel for information transfer between nuclear facility operators at Mochovce and population living around. Establishment of the Committee was inspired by good practice from some countries, where similar committees had been established on voluntary or legislative basis.

The Mochovce CIC was established on 1 January 2005 and consists of representatives of the public (mayors) who are independent from nuclear operators and active in public life. The Committee members are the following: Regional association of municipalities Mochovce, Slovenske elektrarne and JAVYS.

The purpose of the Committee is to lead open dialogue with the public about peaceful use of nuclear energy and transfer qualified and current information about nuclear developments to the public, taking into account the right of citizens to be informed truly and immediately about all aspects construction and operation of nuclear facilities, safety and environmental impact of the nuclear facilities though the delegated representatives of the public.

For more information about the Association of municipalities Mochovce and Civic Information Committee see