Key milestones reached in 2025

Unit 4

• Small Revision started on 02.01.2025 and was completed on 26.02.2025
• Hot Hydro tests started on 15.03.2025 and was completed on 25.05.2025
• Extended Revision started on 28.05.2025 and was completed on 25.07.2025

Key milestones reached in 2024

UNIT 3

Key milestones reached in 2023

UNIT 3

Key milestones reached in 2022

UNIT 3

Key milestones reached in 2021

UNIT 3

• On 13 May 2021, the Slovak Nuclear Regulatory Authority, after verifying the fulfilment of all technical and legislative requirements, issued the Decision No. 156/2021 - the permit for commissioning of Unit 3 of the Mochovce Nuclear Power Plant, as well as the related permits for radioactive waste and spent nuclear fuel management and for the early use of the construction.
• On 28 May 2021, the Slovak Nuclear Regulatory Authority received an appeal by the Austrian anti-nuclear organisation GLOBAL 2000 against the decision and the same party to the proceedings delivered a supplement to the appeal against the decision on 11 June 2021.

Key milestones reached in 2020

UNIT 3

• Completion of primary circuit re-heating.
• 3-week international review of readiness for commissioning by a team of IAEA experts Pre-OSART.
• Rectification of pending issues from last year’s hydrotesting and inspections.
• Replacement of pressurizer electric heaters.
• Completion of cooling tower distribution channel reinforcement.
• Completed cabling for Unit 3 operation.
• Repair of welds at service water piping.
• Completed upgrade and testing of control room simulator for personnel training.
• Confirmation of HVAC system tests at conventional part.
• EMC (electromagnetic compatibility) tests.
• Verification of some small diameter piping components with spectrum analysers, as well as all material certificates.
• Draft permit of the Nuclear Regulatory Authority for fuel loading at the Unit 3.

Completion progress as of December 2019

• Unit 3: 99.3 %
• Unit 4: 87.1 %

Key milestones reached in 2019

UNIT 3

• Hot hydro – all planned tests performed.
• Extended revision – inspection and evaluation of primary circuit equipment successfully completed.
• Application for preliminary use of civil structures – all local inspections performed by relevant authorities.
• Handover of systems to future Operation team in progress.
• Fresh nuclear fuel storage authorized by the Nuclear Regulatory Authority (ÚJD SR).
• Turbines in turning gear ready to receive steam.
• Boric acid preparation for fuel loading.
• Public consulting with on-site walkdown by stakeholders.
• Review of readiness for fuel loading by the International Atomic Energy Agency (Pre-OSART Mission).

UNIT 4

• More than 1000 km of cables pulled in 2019.
• All electrical panels of Distributed Control System installed and tested.
• Installation of fire detection and fire-fighting systems needed for energization.
• Essential service water mechanical assembly completed.
• 250 tons of steel structures installed for seismic reinforcement in conventional island.

Completion progress as of December 2018

• Unit 3: 98,23 %
• Unit 4: 86,6 %

Key milestones reached in 2018

UNIT 3

• NPP physical security system in operation
• Cold Hydro tests successfully completed
• Fresh Fuel Storage ready for fuel delivery
• All loop checks for Cold and Hot hydro tests completed
• Small revision (consisting mainly of disassembly, pre-service inspection and assembly of reactor, pressurizer and steamgenerators)
• Start of Hot Hydrotest

UNIT 4

• Completion of 110kV/400kV substation and transformer area
• Small bore piping completed in Nuclear Island
• More than 1000 km of cables pulled

Completion progress as of December 2017

• Unit 3: 96.1%
• Unit 4: 84.5 %

Key milestones reached in 2017

UNIT 3

• Primary (reactor coolant) circuit pressure test
• Hydrogen recombiner system flushing
• Integrated thermal cycle flushing completed
• Chemical and volume control system flushing
• Fire water station takeover
• Takeover of key emergency cooling and spray systems
• Connection to 400kV power transmission system
• Initial phase of the cold hydro testing of the primary circuit

UNIT 4

• Assembly of high-pressure air system
• Reactor control assembly
• Large bore piping erection
• Civil readiness for distributed control system rooms
• Completion of main cable trays in conventional island

1^st quarter

• Erection of fire detection system in the fresh fuel storage.
• Revisions and cleanings of the main circulation pumps at Unit 3.
• Turnover Low Pressure Air system.
• Turnover DemiWater distribution system.

2^nd quarter

• Reactor control assembly completed.
• Flushing of thermal cycle started.
• Functional Tests of Medium Voltage switchboards completed.
• Installation of the fuel loading rails at Unit 4.
• Installation of impulse pipelines in the hydrogen recombination system.
• Insulation of low-pressure reheaters at the Unit 3 turbine hall.
• Flushing of pure condensate distribution system completed.
• At Unit 4, the main circulation pumps were transported.

3^rd quarter

• Successfully passed functional tests in Unit 3: 110 kV substation for Units 2 and 4, fire protection system and HVAC unit in room No. 1305
• Radiation monitoring system finished in several rooms of the power block.
• Lengthwise side electrical building of Unit 3: painting of steel sections, plasters, disassembly of scaffolding, lying of cables, recovery of partitions
• Crosswise side electrical building of Unit 3: installation of pipes and supports, installation of channels
• Unit 3 commissioning: tests and installation works at the reactor and facilities of the concrete reactor cavity finished, testing of 19 home consumption power switchboards, put of other electronic fire protection system detectors into operation to activate the power home consumption  
• Unit 4: installation of steel structures of HVAC
• Completion status: Unit 3: 93.7 %, Unit 4: 79.2 %

 4^th quarter

• Finishing of the boron acid treatment plant.
• Diesel generator station of Unit 3: installation of switchboards, measuring and excitation transformer and cable trenches
• Unit 3 commissioning: functional tests of 6 kV switchboards, functional tests of secondary and section switchboards
• Turbine hall of Units 3&4: insulation of pipes, flushing, conformity check, installation of small diameter pipes, lying of cables, individual tests of switchboards, connection of switchboards
• Refurbishment of the cooling tower pool.
• Completion status: Unit 3: 94.1 %; Unit 4: 80.7 %

• Insulation of tanks for the Standby water system.
• Erection and welding of stainless steel lining of the Unit 3 spent fuel pool.
• Installation of 36.000 new anchoring plates for Unit 3 completed.
• Demineralized water system was installed for turbogenerator TG41.
• Construction test and hydrotest of the emergency feedwater system tank Erection of anti-aircraft barriers
• Delivery of a new TG32 turbogenerator for unit 3.
• The control room of unit 3 was energized, and the nuclear project entered the testing and commissioning phase. Individual tests of the I&C system commenced.
• Installation of common diesel generator.
• Under the supervision of the Nuclear Regulatory Authority of the Slovak Republic, Slovenské elektrárne verified the special professional skills of its shift engineers, unit heads and unit operators. The verification has to be done one year before the commencement of physical commissioning of the reactor unit.In unit 3, conditions for clean assembly in the reactor hall were reached.

• Completion of Full Scope Simulator site acceptance testing.
• Commencement of functional tests of medium voltage switchboards at Mochovce Power Plant Unit 3.
• Unit 3 Control Rooms (main control room, emergency control room, common control room) assembled for start of Commissioning activities.
• Start of Mochovce 3&4 operators training at the Full Scope Simulator; following the completion of licensing process for operators training by the Nuclear Regulatory Authority of the Slovak Republic.
• Submission of "Pre-Operational Safety Analysis Report" to the Nuclear Regulatory Authority of the Slovak Republic. The document is the key for authorization of Fuel Loading to Unit 3.
• Unit 3 Main Control System: 90 % of internal cabling of Unit 3 Main Control System (total: 9.000 cables) completed.
• Unit 3 Nuclear Island: Civil Readiness of over 90 % of NI rooms needed for Unit 3 Commissioning. Instrumentation room (1 out of 3) with impulse lines, penetrations impulse lines and racks completed. The room is ready for the installation of the instruments. Radioactive waste treatment piping installed.
• Reactor hall civil works completed which is the first step towards Strict Clean Conditions required for Reactor internals works.
• Unit 3 Conventional Island: First phase of 6kV busbars commissioning completed. Mechanical completion of the main systems (non-essential and essential service water, main steam, feed-water, condensate, high and low pressure air systems). Up to 100 km of main cable trays erected (100 %).
• As of the end of 2014, the Unit 3 was 81% and the Unit 4 was 63% completed.

• Civil readiness of Unit 3 Nuclear island critical rooms.
• Completed the Detailed Design of Unit 3 Anchoring Plates.
• Start of mechanical erection activities in the Nuclear island critical rooms.
• TG31 and TG32 Final assembly, bearing closing, turning gear installation, insulation assembly.
• Completion of Mechanical Erection of Unit 3 Main Steam and Feedwater systems.
• Individial tests of Unit 3 LV/MV Cabinets.
• Unit 3 – Distributed control system power up.
• Full Scope Simulator
  • Application Software Installed and Tested;
  • Site Acceptance Tests.
• Refurbishment of hermetic cable penetrations at the Units 3&4.

• Fire protection lining and painting in auxiliary nuclear building
• Civil readiness for foundations under pipe bridge
• Concrete floor drainage in room A217
• Transport and assembly of 7th section of spent fuel pool in Unit 4
• Installation of instrumentation and control system cabinets
• Welding of stainless-steel lining floors on Unit 4 in A201/2, A301/2
• Grouting activities - works under the tripods of primary circuit of Unit 4
• Assembly of penetrations on the shaft no. 1 of Unit 4
• Concreting of floors and vertical elements in the vent stack
• Modernization of main circulation pump 3, 6
• Refurbishment of main circulation piping
• Erection of diagnostic system on steam generator 6
• Welding of support ring under core basket
• Erection of removable part of main circulation pump 2-6
• Three stand supports straining of main circulation pumps 1-6
• Transport of frames and pumps of sprinkler and low pressure emergency injection system
• Erection of bellows
• Blowing through the steam generator 1
• Commissioning of 110 kV back-up electric source
• Concreting of Unit 3 reactor postament
• Installation of 400kV electric switch yard
• Fresh nuclear fuel storage prepared for technology installation
• Assembly of all four steam turbines of Units 3 & 4 completed
• Safe Enterprise certificate for SE-MO34 site

• Refurbishment of internal walls of vent stack;
• Refurbishment of roof of nuclear auxiliary building;
• Refurbishment works of condensate tanks on the roof of auxiliary nuclear building;
• Seismic reinforcement of reactor building;
• Seismic reinforcement of internal walls of auxiliary nuclear building;
• Refurbishment of internal walls of connecting bridge;
• Installation of earthing networks of vent stack;
• Civil readiness of the emergency room in a simulator building;
• Hydrotest of spent fuel pool of Unit3 (shaft No. 1);
• Grouting of mechanical equipments (primary coolant pumps);
• Civil readiness for refurbishment of reactor upper block;
• Refurbishment of hermetic and non-hermetic zone in reactor building (Unit 3,4);
• Foundations for pipe bridge; 
• Refurbishment of external walls of auxiliary nuclear building;
• Internal seismic reinforcement of connection bridge;
• Erection of fire protection lining in auxiliary nuclear building;
• Concreting works on postament of unit 3;
• Heavy concreting on postament of Unit 4;
• Reinforcement on postament of Unit 4 around shaft no.1;
• Concreting works around reactor pit of Unit 3;
• Erection and welding of main circulation piping in the steam generator box;
• Reactor pressure vessel of unit 4 transport and placement (2-3/12/2011);
• First turbine of Unit 3 installation (December 2011).

• Seismic reinforcement of reactor building roof;
• Seismic reinforcement of external structures of reactor building;
• Seismic reinforcement of steel structures of the turbine hall;
• Erection of new bridge crane in turbine hall;
• Refurbishment of turbines supports;
• Seismic reinforcement of internal steel structures of auxiliary nuclear building;
• Refurbishment of steam generators (unit 3);
• Refurbishment of 250t crane in the reactor hall;
• Reinforcement of roads, corridors and slabs for the reactor pressure vessel transport;
• Refurbishment of auxiliary structures for transport of reactor pressure vessel;
• Refurbishment of external walls of vent stack;
• Refurbishment of cooling towers;
• Reactor pressure vessel of unit 3 transport and placement (3-4/9/2010);
• Refurbishment of anchoring structures of steam generators (unit 3);
• Refurbishment of bubble condenser (unit 3);
• Refurbishment of external walls of reactor building;
• Removal of old moisture separators and reheaters (unit 3);
• Refurbishment of hermetic penetrations;
• Refurbished rooms in reactor building, number of rooms ready for mechanical erection:
  • Unit 3: 328 out of 353;
  • Unit 4: 197 out of 239.

• Main nuclear island contracts, EPCM contract for the conventional island and main I&C Engineering contract were signed and activities have started;
• Contractors' mobilization works completed (site services, site offices, ...);
• Evaluation of existing components;
• Refurbishment of reactor hall roof;
• Seismic reinforcement of the external walls of the reactor building.