21 Apr (NucNet): Fortum has completed construction of a unique new emergency air-cooling system at the twin-unit Loviisa nuclear power station in Finland, the company said today.
The system, which is the first of its kind at a nuclear plant, includes two forced-air cooling towers per unit, which will be used for removing decay heat from the reactor and the spent fuel pools and cooling of other equipment critical to nuclear safety.
The system will provide cooling in extreme conditions when seawater becomes unavailable for cooling, for instance if there is as an oil catastrophe in the Gulf of Finland, or an exceptional natural phenomenon such as excessive algal bloom, Fortum said.
Loviisa, which has two 496-megawatt VVER pressurised water reactor units, already had back-up systems in place for the seawater cooling. The new air-cooled system further supplements those back-up systems, Fortum said.
Fortum, which operates the Loviisa station, said it has studied and developed the new independent cooling system concept for several years. It considered various alternative options, including the use of onsite water storage, a nearby lake and even a plan to dump the heat back into the bedrock, but it said that the air-cooling option offered the only long-term solution for decay heat removal.
The project became a development target following safety assessments carried out by the Finnish Radiation Safety Authority (Stuk) in 2012 as a part of the post-Fukushima stress tests within the European Union.
The cooling towers were supplied by the Hungarian firm GEA EGI Contracting/ Engineering Co. Ltd, and were installed by Finland-based Caverion, under a contract said to be worth €2 million ($2.1 million).
One cooling tower is connected to the reserve residual heat removal system (RR) and the other to the intermediate component cooling system (TF) in each unit.
Fortum said the reserve residual heat removal system removes decay heat generated in the reactor core through the secondary circuit after shutdown of the reactor. Heat is transferred from the reactor core by natural convection to the primary circuit and into the steam generators.
The RR system cools the secondary side of the steam generators. A seawater circuit (VF) then transfers the heat to the seawater. If seawater is not available, the RR air cooling tower will provide cooling to the RR circuit by replacing the VF connection.
Fortum 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 plant.
The solution is a cost-efficient way to increase the safety of the seawater-cooled nuclear power plant,” said Fortum group manager Samuli Savolainen.
Final capacity and warranty testing of the new system will be conducted during an annual outage scheduled for this summer.
