Mochovce Nuclear Power Plant Construction

The overall investment costs of Units 3 and 4 of the Mochovce Nuclear Power Plant were approved at €4,6 billion, the total cost progress as of December 2015 reached 3,503 mln euro. It is the largest investment in the private sector in Slovakia, the power plant that will contribute 26% of Slovakia’s power demand.

Hours worked in 2015 exceeded 12.5 milion overall with the peak number of overall employees at the construction site (direct and indirect) amounting to more than 6.890. Total number of hours worked from the beginning of the project is around 50.1 milion overall (November 2008 until the end of December 2015).

Project team comprised of over 800 experts from Slovenske elektrárne, its subsidiary SE SIS and Enel ER. The construction involved approximately 190 contractors. More than 48% of contracts were awarded to Slovak companies.

Innovative technology

Gross capacity at the Commercial Operation Date will be 2 x 471 MW, each reactor designed to reach 530 MW. Technology used is VVER 440-213. Reactor is moderated and cooled by pressurized water. Technology of MO 3,4 is upgraded Generation III, which means:

  • Evolutionary design through proven technology and safety upgrades.

  • Inherently safe basic characteristics: low power density and large thermal capacity of primary circuit;

  • availability and efficiency: improved outage and maintenance Schedule.

Most significant activities and milestones in 2015

At the end of 2015, overall physical progress at Unit 3 reached 90.5 % and 72.2% at Unit 4. With Unit 3 erection completion, Unit 4 erection will increase significantly. Erection activities at Unit 3 accelerated significantly in 2015 to an average progress of 2% per month.

The most important milestone of 2015 was the energization of Unit 3 main control room. We successfully brought power supply from the external electrical lines through the medium and low voltage switchboards to the control system. The individual systems will be gradually connected to the control room and their testing and commissioning will be controlled from there.


control assembly activities. The main equipment involved in first phase of clean assembly were the reactor pressure vessel, reactor shaft, reactor shaft bottom, core cage, tube protection block and reactor upper block.

Rate of cable pulling in Unit 3 significantly increased, reaching 73% of completion in the Conventional Island. Concrete pouring of the reactor postament of Unit 4 was completed. Postament is a civil structure which surrounds the upper part of the containment around the reactor. The portion completed extends for more than 10 metres in height and it consists of almost 1000 cubic metres of concrete.

The tests at the MO34 simulator were successfully passed by shift supervisors, reactor unit supervisor, as well as reactor and turbine operators.

Mochovce poster

Nuclear Energy Projects

Projects Resulting from European Stress Tests

The stress test results from 2011 following Fukushima nuclear power plant accident and recommendations from the European Nuclear Safety Regulators Group (ENSREG) were used as the basis to prepare an Action Plan the final version of which was submitted to the Nuclear Regulatory Authority in December 2012. The Authority carries out regular inspections to verify the factual fulfilment of the items in the Action Plan and their performance to schedule.

The measures also include very sophisticated projects, such as Severe Accident Management Programme (SAM), whose implementation was accelerated after events in Fukushima and today they are already completed in both power plants. Among them is the installation of autocatalytic recombiners for hydrogen reduction, new systems to ensure supply of coolant and increase reliability of heat transfer, increasing of reliability of power supply to important appliances though installation of new sources of power, such as 6 kV diesel generators and 0.4 kV mobile diesel generators with required electrical equipment. Other project are the Seismic Resistance Increase in EMO 1,2 and new measures aimed mainly at safeguarding that critical safety functions of power plants are covered by diversified sources in extreme external events.

The ability of the nuclear power plants to withstand extreme meteorological phenomena with a probability greater than 10-4 was analyzed. Alongside the implementation of the specific measures in the Action Plan, work is being undertaken also to develop the advanced support instruments to manage a potential accident and to update the manuals for managing severe accidents and to integrate them with documents on severe accident management in order to comply with the updated WENRA and WANO requirements.

By the end of 2015 seven projects out of eighteen, selected ones were implemented, five projects are ready for full implementation during the general overhaul in 2016 and remaining five projects are in advanced stage of procurement or project documentation preparation in Bohunice power plant.

By the end of 2015 eight projects out of twenty-two selected ones were implemented, four projects are ready for complete implementation during the general overhaul in 2016 and remaining ten projects are in advanced stage of procurement or project documentation preparation in .

V2 Bohunice Nuclear Power Plant

In 2015 work continued on projects according to the investment plan for the power plant, with aim to allow further safe, ecological and efficient generation of the electricity and heat.

In accordance with the results of the periodic evaluation of operation of the nuclear installation at the end of its forecast life, preparation and implementation of projects which resulted from the programme aimed at long-term operation of the power plant commenced.

The project for replacement and revitalisation of pipelines for the essential service water belongs among the most significant ones; the project and legislative development was fully ensured, the implementation of the parts of the project which may be done out of the general overhaul has already commenced. It is scheduled to complete this project during the joined outage of both V2 NPP units in 2016.

The project and legislative preparation was ensured for the project of the reactor protection system replacement and cable replacement for the emergency and control assemblies in both units of V2 NPP; it will be carried out during the joined general overhaul of units in 2016.

During 2015 the works continued on projects for the separation of the V1 and V2 power plants and the related need to construct separate systems for the V2 Nuclear Power Plant.

The premises for contractors, the storage area for contractors were handed over for their use and the new waste management facility was completed and taken over.

Building of the new maintenance storage hall including the chemical substances storage is in its final stage, with completion is scheduled for 2016. The projects for new back-up supply system of the power plant continued; their project and legislative development was completed in 2015. Construction of a new 110 kV substation on site of the V2 nuclear power plant as well as installation of the new 110 kV line and technologies for connection of new back-up transformer started.

To ensure a sufficient efficiency of the cooling towers in adverse winter conditions, the project for reconstruction of the winter spray system of the last cooling towers was completed.

Mochovce Nuclear Power Plant Units 1 and 2

The main investment at the operational units 1 and 2 of the Mochovce Nuclear Power Plant in 2015 continued to be aimed at increasing the units´ safety, operational availability and reliability.

As part of the severe accident management (SAM) programme some supplementation projects were carried out for the primary coolant circuit depressurization system, the vacuum prevention system in the hermetic zone, the emergency coolant source and the emergency power supply, I&C system, long-term heat removal system in the hermetic zone of the primary circuit.

In the field of minimising the radioactive waste generation, the project preparation was completed for the project of radioactive waste concentrate processing, its implementation is scheduled for the next period.

Regarding elimination of external risks, the project for seismic reinforcement continued to increase the value of seismic load. In 2015 the construction modifications and seismic reinforcement were completed in the fire station and it was extended for placing the mobile sources of coolants and mobile diesel generators.

Further stages of the project for the replacement of diesel generator automatic systems and the replacement of the 0.4 kV section distributors continued during the planned outages of units and partly outside the outages.

With regard to efforts to increase the operational reliability and the availability of resources, the moisture separator and re-heater on of turbine generator TG12 were replaced and hydrogen burning system were modernized.

Conventional Projects

Nováky Thermal Power Plant

The most important investment in the Novaky Power Plant (ENO) in 2015 was the modernisation of the units 1 and 2 of ENO B. The goal was to meet new European emission limits valid from 2016.

To decrease limits of nitrogen oxides from 400 mg/m3 to new limits of 200 mg/m3, a selective non-catalytic reduction method was used, new low emission burners were installed, new lines for recirculation of gases were installed. To decrease particulate matter from 50 mg/m3 to 20 mg/m3, new electric separators. To decrease SOx limits from 400 mg/m3 to 200 mg/m3, a modification of desulphurisation technology was carried out and the control system was replaced. New emission measurement system was installed in both units. A general overhaul of the turbine generator TG1 turbine and replacement of generator coil was done during outage of unit 1.

Year 2015 marked the completion of the reconstruction of 110 kV substation, which created technical conditions for continuation of safe and reliable operation of substations and facilitites allowing changes of configurations of power lines in order to cover own consumption.

To ensure steady supply of coal in winter, a project of reconstruction of defrosting tunnels was completed successfully, replacing the old one, which uses the technology of infrared heating with higher efficiency in coal defrosting.

Since the operation of ENO B units 3 and 4 was terminated due to non-compliance with new strict ecological limits, a new backup source of heat was installed which will enable to start at least one of the three remaining units from cold state and thus renew the production of heat and electricity in the power plant.

Vojany Thermal Power Plant.

In 2015, Vojany power plant (EVO) focused on optimisation of the internal consumption. The sum of the implemented technical measures led to increase of the power plant efficiency by two percentage points up to 29.51% in comparison to 2014.

In order to improve the economic management of EVO, a successful co-combustion test of biologically degradable waste was carried out. The co-combustion tests proved the ability of fluidised bed boilers to burn the biologically degradable waste. Preparation of a homogeneous mixture of the biologically degradable waste with wood chips and transportation of the mixture to the reservoirs of the raw fuel and to the boiler was successfully tested. The tests proved that the emission limits, boiler efficiency and provision of the ancillary services were regarded when using this mixture.

In December an important project took place and the regulation band of B5 unit was extended from former 50 – 110 MW to 40 – 110 MWe, while the capability for provision of the ancillary services of the primary and secondary capacity regulation was preserved.

Hydroelectric Power Plants

The beginning of 2015 was very demanding for hydro power plants. The hydro power plants had to manage all the activities related to carving Gabčíkovo power plant out of Slovenské elektrárne portfolio. Then the organisational structure of the hydro power plants was optimised. Two operation units were established. Váh operation unit manages operation and maintenance of hydro power plant situated on the Váh river and the PS HPP operation unit manages operation and maintenance of the pumped storage hydroelectric power plants.

In 2015 an extended common repair of turbine generator TG2 at Lipovec hydro power plant was successfully completed; the common repairs at Ružín II small hydro power plant started as well as repairs of turbine generator TG2 at Nosice HPP the completion of which is scheduled for 2016.

Replacement of the unit transformers and the project for implementation of the unified access system continued in hydro power plants. At the end of the year the ancillary service for black start was successfully certified in Čierny Váh pumped storage power plant.

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