The construction of a nuclear power plant is a huge industrial investment similar to the bioproduct mill in Äänekoski, but the construction of a nuclear power plant will take longer and employ more people than the construction of the large industrial plant.
The construction work in the plant area will start when a construction license based on the Nuclear Energy Act has been granted. During the year after the granting of the license, the number of people working at the construction site will increase to 1,500. At best, some 4,000 people will be simultaneously doing construction and installation work at the construction site, probably during the fourth year after the start of construction.
First, a concrete slab that is several meters thick must be poured. When this has been done, construction of the buildings can be started: the reactor building and the steam generator building, quickly followed by the control room building, the safeguard building, and the turbine building.
Hanhikivi 1 nuclear power area will be built from downwards up
According to the plan, more than a hundred buildings will be constructed side by side in the plant area over the course of five years. The order in which the buildings will be constructed and the schedules in general have been planned with exceptional care.
“The rule of thumb in construction will be proceeding from downwards up and from buildings in the middle of the area to those at the edges. The construction of the buildings that will take the longest to complete will be started early, regardless of their location,” says Petri Jyrälä, Fennovoima’s Engineering Director.
Many factors must be considered in addition to the lack of space in the plant area. Many components will be brought – or lifted into – the buildings while the walls are still being built. Testing of components and systems will also be part of the everyday life of the busy construction site.
“Making sure that all the components to be installed at an early stage are appropriately protected and stored is important to ensure that the components will still be intact and operable at the testing phase,” Jyrälä explains.
The installation work in the reactor building will take five years
When taking into account the preparatory work, installation of the reactor pressure vessel will take approximately one month, but it has been estimated that the mechanical installation work in the reactor building will take almost five years in all. Electrical installation work will take almost four years. In the turbine building, installation of the turbine will take approximately two years and installation of the generator approximately twelve months.
The power plant’s components will arrive as shipments of varying sizes. Most of the components delivered in one piece weigh hundreds of metric tons and can be more than ten meters tall or long.
Components will be delivered by sea to be unloaded at the construction site’s own pier or at ports in the neighboring towns. Most of the building supplies will be transported by road, but plenty of supplies will also be made at the Hanhikivi peninsula. An onsite concrete mixing plant has already been completed, for instance, and a concrete reinforcement plant is currently under construction.
Concrete structures have an important role in building a nuclear power plant
The reactor building is the most demanding structure of the plant area. The casting of the steel-concrete containment alone consists of several inspection phases. Many of the plant area buildings have more stringent strength and other special requirements compared to conventional industrial projects. Concrete has an essential role in the building of the entire nuclear power plant.
The reactor unit will have a thick double-shelled containment building that is several meters thick. The inner containment building made from reinforced concrete will be a prestressed cylinder with an elliptical cover. It has been designed to withstand temperature and pressure loads that may be caused by pipe breaks. The outer containment building will be a reinforced concrete cylinder that provides protection against external hazards. Both containment buildings will share a base slab.
More than a hundred buildings will be constructed side by side in the plant area over the course of five years.
Preventing release of gaseous material sets extreme requirements on the leaktightness of the containment building, which has an inner liner of steel for this reason. A large number of prestressing cables will be assembled in protection tubes installed inside the concrete wall of the inner containment. Leaktightness of the containment will be monitored, and any leaks will be stopped in the annular space of the containment, i.e. the space between the inner and outer shells of the containment building.
The casting of the concrete shells and the installations of the steel liner and the protection tubes will proceed synchronously from downwards up. This construction phase will be finalized by casting a double dome on the top.
Extensive commissioning phase after testing Hanhikivi 1 nuclear power plant
Testing of the components and systems will start when construction work is still ongoing. The components will be tested first, followed by sub-systems and finally the entire systems. The first commissioning test of the power plant will start before the nuclear fuel has even arrived at the plant. At that time, the construction work will be mostly complete, and there will be a double fence around the plant area and the rest of the site.
When the Radiation and Nuclear Safety Authority (STUK) has given its permit on the basis of the commissioning test results, the fuel will be brought in and loaded into the reactor pressure vessel. This will signal the start of a two-phase nuclear commissioning test. Only after that can the power plant be finally approved and commissioned for regular commercial electricity production.
An interim storage facility for spent nuclear fuel and a final disposal facility for low- and intermediate-level operational waste will be completed later on the Hanhikivi peninsula.
Hanhikivi 1 nuclear power plant
- The nuclear power plant will have a VVER-1200 reactor, which is a pressurized water reactor.
- The reactor generates heat from the nuclear fuel. The heat is generated when uranium atoms split.
- The reactor heats up water in the main circulation or primary circuit piping, but the water does not vaporize due to the high pressure inside the piping. The hot water is pumped into a steam generator, where the heat is transferred through a wall to the secondary circuit piping, vaporizing the water in the secondary circuit. The steam goes further into the turbine building. Both piping systems are closed cycles.
- The steam rotates a turbine that rotates a generator mounted onto the same shaft. This turns the kinetic energy into electricity that is transferred via a converter into the power grid.
- Seawater that is pumped into the condenser in the turbine building cools down the steam so that it changes back into water. The water is returned to the steam generator in the reactor building. The cooling water from the circulating water system is returned to the sea. The water in the circulating water system does not get into direct contact with the water in the primary or secondary circuit at any time.
- The power plant’s capacity will be 1,200 megawatts (MW).
- The plant supplier is RAOS Project, a subsidiary of Rosatom. The main contractor is Titan-2.
Hanhikivi 1 plant area
- The nuclear power plant and the more than 140 buildings to support its operation will be located in a plant area of 23 hectares. Surrounded by a double fence, the plant area will be located inside the 95-hectare site area.
- The plant area has been divided into three sectors: the reactor and turbine island, as well as supporting and auxiliary buildings.
- Reactor building will be a little over 70 meters in height and 54 meters in diameter. The island will consist of approximately 20 buildings.
- The turbine building will be 130 meters long and 60 meters wide, and it will house the steam turbine and the generator. The turbine island will consist of approximately 20 buildings.
- There will also be a little over 90 other buildings in the plant area.
- The tallest structure in the plant area will be the ventilation stack, reaching a height of 100 meters. The tallest structure in the entire site area will be a weather mast with a height of 124 meters.