Mochovce NPP: The turbine is spinning at Unit 3

03/07/2019
Mochovce NPP: The turbine is spinning at Unit 3
At Mochovce 3, Slovenské elektrárne has successfully started the turbine and the circulation pump, and also filled the cooling tower.

In order to start a turbine in a nuclear power plant, you must first start it with a rotator to reach fifty-three rotations per minute. Only then you can let in the hot steam that will push the turbine blades. At full operation, they will spin three thousand times per minute.

The turbine of unit three at the Mochovce nuclear power plant started rotating for the first time in second half of June 2019. The news was presented on 2 July also to the MPs of the Slovak Parliamentary Committee for Economic Affairs who came to visit the nuclear construction site.

It’s running but not yet generating power

Spinning at a rate comparable to the human heartbeat – fifty-three per minute – preparations are being made to put the whole nuclear unit into operation. The turbine was started first by a button located directly at the turbine’s site, but then also through the main control room, which is the “brain” of the entire power plant. It controls everything – starting from the reactor through to the turbine and finishing with the cooling towers.

The first spinning of turbines is important for the commissioning of the new nuclear power plant and it allowed Slovenské elektrárne to continue with the scheduled tests.

At the control room – the launching of turbines of Mochovce NPP unit three.

At the control room – the launching of turbines of Mochovce NPP unit three.

Steam does not come from the reactor

Let’s talk a bit more about turbo generators of the new Mochovce power plant. Under each turbine there is a condenser. The condenser gathers the condensation of the “exhausted” steam that has been spinning the blades of the turbine’s impellers. This type of steam needs to be liquefied so that it can be afterwards reheated again and changed to steam in the steam generators, subsequently using the steam pressure to spin the turbine generators. Round and round, 345 days a year (the remaining days are taken by planned overhauls and refuelling).

When the steam passes its heat onto the condenser, how will it be cooled?

Well, this is the moment when the iconic image of nuclear power plant in Slovakia, more than one hundred and twenty metre tall cooling towers come into play. Many people passing by Mochovce or Bohunice nuclear power plants presume that reactors are hiding directly under these towers. The truth is though, the cooling tower simply cools water. More precisely, it fans the water through the natural air flow. In order to increase the cooling effect, the cooling towers are shaped as a nozzle with clouds of water aerosol rising above the installation’s panorama. The towers thus serve only for cooling the condensers.

And what about the reactor?

Well, the reactor is to be found somewhere else, in separate constructions, hundreds of metres away, enclosed in ferroconcrete containments. In June 2019, the cooling towers at Mochovce were related to yet another success in completion of the new nuclear power plant.…

Standing next to the turbine at Mochovce – Launch of the EMO TG31 rotator.

Standing next to the turbine at Mochovce – Launch of the EMO TG31 rotator.

Premiere filling of the unit three cooling tower

In June 2019, Slovenské elektrárne filled the cooling tower of Mochovce Unit 3 to its operational level. The huge pumps used for pumping water from the cooling tower to the condenser were turned on. It was also the premiere launch of the pump from the main control room.

About the pumps.

These are the the two largest engines at Mochovce Unit 3, used to push massive amounts of water through pipes that are two hundred and twenty centimetres wide in diameter. Each pump consumes almost five megawatts of the approximately five hundred megawatt output of each reactor unit. It means that one pump consumes as much electricity per one hour as two average Slovak households per entire year.

This is what the start-up of water circulation pump no. 3 at Mochovce unit 3 looks like at the screen inside the control room.

This is what the start-up of water circulation pump at Mochovce unit 3 looks like at the screen inside the control room.

Seventeen swimming pools per hour

No wonder that it needs a lot of juice when the pump, at its maximum flow, pushes some thirty-five thousand cubic metres per hour, i.e. thirty-five thousand tonnes of water from the cooling tower to the condenser. To have a better picture of what that means, imagine seventeen swimming pools filled in sixty minutes, or the weight of four hundred and forty Boeing 737s.

All that is needed to cool down the water for the condenser, to a temperature not higher than thirty-three degrees Celsius.

From the right: Mr. Branislav Strýček, Slovenské elektrárne CEO; Ms. Marta Žiaková, Head of the Slovak Nuclear Regulatory Authority; and Mr. Karol Galek from the Slovak Parliamentary Committee at the press briefing after a visit to Mochovce on 2 July 2019.

From the right: Mr. Branislav Strýček, Slovenské elektrárne CEO; Ms. Marta Žiaková, Head of the Slovak Nuclear Regulatory Authority; and Mr. Karol Galek from the Slovak Parliamentary Committee at the press briefing after a visit to Mochovce on 2 July 2019.