New cooling towers completed at Loviisa

Wednesday, 22 April 2015

The construction of a new backup air-cooling system independent of seawater cooling has been completed at the Loviisa plant in Finland.

One of the new air cooling towers at the Loviisa (Image: Fortum)

The Loviisa plant already has backup systems for seawater cooling, but the new air cooling system further enhances the safe use of the plant, Fortum said. The new system can be used "in the improbable extreme situation when seawater wouldn't be available to cool the plant's reactors," the company noted. For example, an oil catastrophe in the Gulf of Finland or an exceptional natural phenomenon like an excessive algal growth.

The new heat exchangers, the cooling towers, are located in three buildings which Fortum says have no significant impact on the landscape of the plant area. The buildings are ten meters wide and 15 meters high. Two cooling towers have been built for each of Loviisa's two units. One tower is used for removing decay heat from the reactor while the other is for removing decay heat from the used fuel storage pools as well as for cooling other safety-critical equipment. The towers used for removing heat from the reactors are located in the same building.

The cooling towers - designed by Fortum and supplied by Hungary's GEA EGI Contracting/Engineering Co Ltd - have been integrated with the power plant's existing systems. The power supply is ensured through the plant reserve systems. Construction of the new towers was completed in February and their final testing will be conducted during an annual outage at the plant later this year.

Any power plant using a steam cycle relies on cooling regardless of whether it uses fossil fuels or nuclear energy to generate that steam. In normal operation, Loviisa's two units use about 40 cubic metres of sea water per second to cool the steam that powers the electricity generation turbines. The cooling water is then returned to the sea about 10ºC warmer, but otherwise unchanged.

Unlike fossil fuelled plants, nuclear reactors also require cooling when shut down, to remove heat generated by radioactive decay. For this reason, nuclear plants are also equipped with emergency core cooling systems to ensure that cooling functions are not lost even if there is a major problem with the primary cooling system. Loviisa already has backup systems in the event of a loss of seawater, but Fortum says that the new air cooling towers will reinforce the plant's safety still further.

Air cooling towers were identified as a development target in safety assessments carried out by Finnish nuclear regulator STUK as part of the European Union program of stress tests in response to the Fukushima Daiichi accident in Japan, although Fortum says it has been studying and developing the new seawater-independent cooling system for several years.

Fortum group manager Samuli Savolainen said, "Air-cooled systems have been used before in other types of power plants, but the kind of cooling towers used at Loviisa are the first in the world at a nuclear power plant. The solution is a cost-efficient way to further enhance the safety of the seawater-cooled nuclear power plant."

Researched and written
by World Nuclear News