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1. Reactor management and controlled reactor shutdown in all conditions.
2. Removal of residual heat, when necessary.
3. Isolation of radioactive substances from the environment.

In Olkiluoto, water cooling is used to cool spent fuel removed from the reactor until it is placed in the final disposal facility. Because of the generation of residual heat, the fuel assembly needs to be cooled in water for about one year. Due to radioactivity, the assemblies are stored underwater also after this.

Preparations for core melting consist at the Olkiluoto 1 and 2 plant units of severe accident management systems. The systems are used to ensure the integrity of the containment and to minimise any releases into the environment. The reactor pressure is reduced automatically, if water level in the reactor decreases. This prevents the rupture of the reactor pressure vessel caused by high pressure and the resulting damage to the containment building.

Hydrogen fires and explosions are prevented by making the containment atmosphere inert with nitrogen. If required, the lower drywell of the containment can be flooded from the suppression pool. This cools the core melt in case it is discharged into the containment following the rupture of the reactor pressure vessel. Water will also protect the penetrations in the containment lower drywell against high temperatures. The penetrations are further protected by mechanical shields. The gas space of the containment is cleaned by filling it with water, which also slows down the rising of pressure inside the containment due to residual output.

If the cooling of the containment cannot be restored, the rupture disks in the top of the containment drywell open at 6 bar pressure to control containment pressure and temperature by allowing steam and gas to escape through a filter and the ventilation stack. The filter will minimise the environmental releases. The filter line is designed to withstand the pressure and temperature prevailing during severe accidents.

The safety and the po­ten­tial risk fac­tors of the Olk­ilu­oto plant units have been as­sessed in many ways. One of the meth­ods used is the prob­a­bilis­tic risk analy­sis, which can be car­ried out to iden­tify and as­sess ac­ci­dent con­di­tions lead­ing to se­vere re­ac­tor core dam­age, and their prob­a­bil­i­ties.

The most re­cent analy­ses car­ried out for the Olk­ilu­oto 1 and 2 plant units give an ac­ci­dent lead­ing to se­vere re­ac­tor core dam­age a prob­a­bil­ity of ca. 1.2*10^-5 per one re­ac­tor year, i.e. per one year of op­er­a­tion at one plant unit. This re­sult means that the prob­a­bil­ity of such an ac­ci­dent in one year is less than one out of 80,000 at one unit.

The rel­a­tive re­duc­tion in the fre­quency of se­vere core dam­age has reduced at the OL1 and OL2 plant units dur­ing the years 1990–2010. Safety up­grades that have con­tributed to the re­duc­tion of the core dam­age fre­quency in­clude e.g. the im­prove­ment of seis­mic re­sis­tance, the im­prove­ment of fire pro­tec­tion, im­prove­ments in the pres­sure vent­ing sys­tems of the re­ac­tors, and the build­ing of a gas tur­bine plant in Olk­ilu­oto to sup­ply power to the safety sys­tems of the Olk­ilu­oto plant units, if nec­es­sary.

Sev­eral mod­i­fi­ca­tions have been im­ple­mented at the plant units that are not re­flected in re­duced core dam­age fre­quency, but have been de­signed to im­prove the man­age­ment of a se­vere re­ac­tor ac­ci­dent and to min­imise en­vi­ron­men­tal con­se­quences. These mod­i­fi­ca­tions in­clude e.g. the re­in­force­ment of the re­ac­tor con­tain­ment against steam ex­plo­sions and the fil­tered con­tain­ment pres­sure re­lief sys­tem, which can be used in ac­ci­dent con­di­tions to re­strict any ra­dioac­tive re­leases into the en­vi­ron­ment caused by the vent­ing of the con­tain­ment.

If required, fire water can be used to cool the fuel in the fuel pools. The capacity of the fuel pools allows any one pool to be emptied at any time with the fuel transferred to the other pools.

The in­terim stor­age fa­cil­ity for spent fuel also has mul­ti­ple and re­dun­dant safety sys­tems just like the power plant units. The cool­ing pools of the stor­age fa­cil­ity have been ex­ca­vated un­der­ground in the bedrock. The pools fea­ture a du­plex cool­ing sys­tem (cool­ing chains) with only one chain needed to cool the pools. In an ex­treme sit­u­a­tion, the cool­ing of the pools can be en­sured by flood­ing them with sea­wa­ter by means of spe­cial arrange­ments.

Over the years, TVO has made many im­prove­ments to the plant units. The in­terim fuel stor­age fa­cil­ity has been expanded. The stor­age fa­cil­ity has been equipped with new safety sys­tems. The safety fea­tures of the pool have been im­proved by pro­vid­ing con­crete cov­ers for the stor­age pools and by re­in­forc­ing ex­ter­nal struc­tures.

The reactor containment of the OL1 and OL2 plant units currently in operation in Olkiluoto is filled with nitrogen during power operation, which prevents hydrogen explosions. The leak-tightness of the containment is ensured by the steel liner embedded in concrete and the steel dome that forms the roof of the containment.

The containment has permanent systems for the controlled combustion of hydrogen released in a potential accident. This prevents the accumulation of combustible gas mixtures in the containment in case of a loss of coolant accident. Hydrogen fires and explosions can thereby be prevented in the reactor building. Pressure and hydrogen can be vented from the containment in an accident through a pressure relief line fitted with a SAM filter (Severe Accident Mitigation).

The generation of hydrogen due to the overheating of spent fuel in the reactor hall pools, as well as any hydrogen fires, are prevented by securing the cooling of fuel.



The systems of OL3 meet all current regulatory requirements and the plant unit has many new safety features. The plant unit has been designed from the start to prevent any significant environmental releases even in case of a severe reactor accident.

OL3 is designed to withstand an earthquake. There are many mutually supporting response arrangements in place for the loss of AC power or cooling water. There are several different backup systems for electrical power supply and several different systems are also available for the cooling of the reactor and for the removal of residual heat from the reactor and the containment.

Particular attention has been paid to the separation and independence of different safety systems. Extreme phenomena have been considered in the design: high seawater level, low seawater level, high outdoor temperature, low outdoor temperature and prolonged snowstorm. The safety of the plant is secured even if seawater cooling is lost.

OL3 is the first plant unit in Europe in which severe reactor accidents have been taken into account in the design from the very beginning. Severe accident management systems are used to ensure the integrity of the containment and to minimise releases into the environment.

During an accident, pressure is reduced in the reactor using the severe accident pressure relief system. This prevents the rupture of the reactor pressure vessel at a high pressure and the resulting damage to the containment building. The plant unit will be equipped with a core melt cooling pool. This so-called core catcher will ensure that even if the reactor core were to melt, it can be cooled down in the containment, thus securing the integrity of the containment.

The containment of OL3 is air-filled. The hydrogen released in a potential severe accident is tackled by hydrogen management systems, which will prevent hydrogen explosions. The containment can withstand hydrogen fires. Hydrogen can be removed from the containment using passive autocatalytic recombinators. Pressure and temperature inside the containment are controlled with a containment cooling system built specifically with severe accidents in mind. In addition, OL3 also features a filtered containment pressure relief system.









Our location on the shore of the Bothnian Sea is quite safe from earthquakes and tsunamis. Finland is located in a seismically stable area and the Baltic Sea is too shallow for a tsunami to develop. Regardless, the earthquake resistance and the safety features of the plant have been improved in many ways over the years. The worst threats that could hit Olkiluoto have been taken into account in engineering as well as in the development and construction of safety systems. Such threats include e.g. storms, floods, freezing conditions, fires and earthquakes.

The Olkiluoto 1 and 2 plant units were not originally designed to withstand earthquakes. Analyses indicate that the modifications carried out ensure that the plant units in Olkiluoto will withstand an earthquake of such a magnitude that the probability of it occurring in Olkiluoto is in the order of one in 100,000 years. The probability of earthquakes has been estimated on the basis of the seismic history of the area, the location of the area in relation to continental shelves and the available geological knowledge. The actual seismic analysis for the plant units was carried out about 15 years ago.

The safety systems of the plant have been constructed to allow for a sea level increase of about four metres from its current level in Olkiluoto. On the plant site, a sea level increase of up to ground level is prepared for, which is approximately four metres above the sea level. Sea level measurements have been carried out in Rauma since 1933. The highest sea level with an increase of 123 centimetres was measured in January 2007.

The height of all the buildings and structures is +10 metres above sea level. Even a 10-metre rise in sea level would not constitute a major safety risk, as Posiva only handles cooled fuel and only in small amounts for short periods at a time. Once the fuel is placed in the transport cask or in the final disposal canister, it is safe from natural disasters.

The Gov­ern­ment De­cree on the safety of a nu­clear power plant re­quires that power com­pa­nies are pre­pared for any con­di­tions caused by the en­vi­ron­ment or hu­man ac­tiv­i­ties that could en­dan­ger the op­er­a­tion of the power plant, and an oil spill oc­cur­ring at sea is one of those po­ten­tial con­di­tions.

TVO has es­ti­mated the pos­si­bil­ity of oil spills in the sea ar­eas sur­round­ing Olk­ilu­oto and their im­pact on plant safety. The im­pact of an oil spill ac­ci­dent on plant safety is mi­nor. In spite of that, TVO has ac­quired oil spill re­sponse equip­ment to be placed not only in the im­me­di­ate vicin­ity of the plant but also on nearby is­lands, be­cause the oil spill equip­ment of the mu­nic­i­pal res­cue ser­vices will prob­a­bly be used else­where in case of an oil dis­as­ter.

The equip­ment con­tain­ers of TVO's re­sponse equip­ment have been placed on the Ku­u­sisen­maa and Lippo is­lands. The oil spill equip­ment will pre­vent any oil dri­ven by the wind from spread­ing to the wa­ter area south of Olk­ilu­oto and from be­ing car­ried from there to the plants in the cool­ing wa­ter. The oil booms have been laid be­tween the fol­low­ing is­lands: Ku­u­sisen­maa - Lippo - Nou­si­ainen - Ko­vakynsi.

Preparedness for different disturbances and the prevention of accidents form the basis for our operation. To this end, each of our plant units is equipped with multiple safety systems that are independent of each other, separated and operate according to different principles. The design basis is the elimination of the possibility of all safety systems being lost for the same reason.

We follow events occurring elsewhere in the world, and if necessary, analyse our own safety systems together with Finnish and international experts and authorities. Should it prove necessary, we develop our own plant units and practices and procedures to ensure an even higher safety level.

The power supply of the emergency cooling systems at our plant has been secured in many ways by means of physically separated electrical systems.

In normal operating conditions, electricity is supplied from the plant unit's own main generator. - If the main generator of the plant unit is not available, electricity is supplied either from the other plant unit or from the national 400 kV or 110 kV grids.
- Both plant units have four diesel generators that start automatically if power supply is lost. - The diesel generators can also be used to supply the other plant unit via the connecting line between the OL1 and OL2 plant units.
- The emergency power station (gas turbine plant) in Olkiluoto can supply electricity to both plant units either via land cable connections or via the 110 kV switching station.
- Certain systems have battery backup.
- By special arrangement, electrical power is also available from the 20 kV network of power company Paneliankosken Voima
- By special arrangement, electrical power is also available from the Harjavalta hydroelectric plant.
- OL3 will have six diesel generators of its own, and it will be connected to the same power supply pool with the existing plant units.







There are no safety deficiencies at the Olkiluoto power plant; these safety assessments have been carried out at all European nuclear power plants. TVO follows a proactive philosophy as regards the development of the safety of the Olkiluoto nuclear power plant and as a result of this takes actively part in all processes designed to improve safety.

TVO has suc­cess­fully fos­tered the cul­ture of con­tin­u­ous im­prove­ment for decades. And as long as we con­tinue to do so, we can vouch for the good, pris­tine con­di­tion of our plants. Our start­ing point is that, from a tech­ni­cal point of view, the plant units al­ways have a fur­ther 40 years of ser­vice life left. Con­tin­u­ous im­prove­ment of safety fea­tures is also part of TVO's cor­po­rate cul­ture.

An airplane crash resistance analysis, among others, has been carried out for the OL1 and OL2 plant units. The buildings were concluded to be extremely strong, but due to security reasons, no details can be given about the analysis, such as the size of the analysed crashing object.

Airplane crash resistance was not one of the original design bases of the plant units, however. Because of this, the crux of the analyses was to assess e.g. the strength of the existing reinforced concrete structures.

The reserves of freshwater stored in Olkiluoto are sufficient to cool the plants and spent fuel for several weeks. In other words, the use of seawater is not necessary by definition.

No, they do not.

TVO's employees are covered by a normal, comprehensive occupational health care system. Employees working in the controlled area are dived into radiation work classes A and B. The monitoring of the health of the employees is based on this work class to verify that they are fit to carry out their intended duties.

A large number of experts are needed to operate and maintain a nuclear power plant. All the employees have their own specific duties and areas of responsibility. Skilled personnel constitutes an important resource. TVO's employees work e.g. in the fields of electrical engineering, mechanical engineering, I&C, process engineering, materials, nuclear technology, nuclear physics, information technology, financial and administrative services, human resources development and communication. In addition to TVO's own personnel, about 800 subcontractor employees work on the island on a permanent basis. Some 1000 subcontractor employees are additionally needed during annual outages. The OL3 project at present employs a good 3300 people.

TVO follows a zero-tolerance policy as far as alcohol and other intoxicating substances are concerned. Random tests are carried out on persons entering the plant units in connection with automatic access control. People who are visiting at the plant units may not be under influence of alcohol either.

Certainly. TVO has women working as licensed reactor operators.

Almost 90%.

They come from different subcontractor companies and their employers are responsible for their employment. Quite a few of the people working in Olkiluoto during the annual outages are employed as outage workers also at other power plants.

Waste generated in the operation of the plant is primarily categorised as low and medium-level waste. Nuclear fuel is categorised as high-level waste

Burning is possible and in some countries low and medium-level waste is burnt. TVO has selected a comprehensive solution based on low and medium-level waste being emplaced as such in the operating waste repository referred to as the VLJ repository.

The silos accommodate the amount of waste generated during the entire service life of the OL1 and OL2 plant units. According to current estimates, the lifespan will be 60 years, i.e. the silos are now about half full. The repository is to be expanded in the future as needed, for example for the operating waste generated at OL3.

Low and medium-level operating waste comprises waste from maintenance activities and filter resin used in the treatment of the process water. The total amount of operating waste generated per year is about 200 cubic-metres. If the waste generated in one year is divided evenly, half a barrel of each waste type is produced every day.

No. Cotton overalls, shoe covers and coats for visitors are washed and reused.

Posiva Oy was founded to carry out the final disposal of spent fuel on behalf of its owner companies, TVO and Fortum Power and Heat Oy. All the expertise in final disposal of nuclear fuel gathered in the founder companies over the decades was transferred to Posiva, when it was founded. No public funding has been or will be used for the operation of Posiva. Read more on Posiva's web site.

Swimming is forbidden on the discharge side for safety reasons due to the strong current of the cooling water. The heat carried to the sea in the cooling water has no adverse effects on the health of anybody swimming in the sea area.

Yes. The heat of the cooling water does not affect fish in any way.

Yes. Grapes, for example, are actually grown in Olkiluoto utilising the heat of the cooling water.

Birdwatchers sometimes see quite rare bird species in the cooling water discharge area in Olkiluoto. A rare butterfly, the Clouded Apollo, is found on the island. Otherwise the nature in Olkiluoto represents a normal environment in Western Finland in terms of fauna and flora.

The seawater used for cooling is not in contact with the process water and does not become radioactive as it runs through the turbine condenser.

Wastewater from the laundry of the power plant, for example, is treated in the waste processing building. The wastewater contains small amounts of radioactive substances. The water is purified and then pumped into the discharge channel of the cooling water.

Radiation does not dissolve in water. Dissolution is a chemical phenomenon and not associated with radiation. In fact, water acts as an excellent barrier to radiation.

No. The amount of radiation is equal to normal background radiation e.g. in the Visitors' Centre in Olkiluoto.

The nearest continuously-operating radiation monitoring points are located within the plant site and the furthest in the town of Rauma, at a distance of ca. 15 km from the plant.

In most work areas yes, but not everywhere. Radiation protection, such as lead mats to cover components with are needed in work carried out during annual outages – rarely during power operation. The need for protective equipment is determined on the basis of radiation measurements before work is started.

Radiation is not contagious and does not make people "radioactive". In order to prevent the employees from carrying any radioactive particles home, all employees have to leave the controlled area through a personnel monitor, which checks their skin and clothing for radioactivity,

On average 1-2 mSv/a (millisievert per year). The maximum permitted annual dose of the employees is 50 mSv; however, the total dose received over a period of five years may not exceed 100 mSv. In practice, the highest radiation doses have been clearly below these limits both in Olkiluoto and in Loviisa. The average annual radiation dose of Finnish people in general is 3.7 mSv. By far the most of this dose comes from natural sources. The radon released from the soil and building materials alone accounts for ca. 2 mSv of the dose. The doses received by the employees are reported in e.g. TVO's social responsibility report.

They have no radiation leave and no extra radiation compensation is paid, either.

No health defects have been found. As a rule, women do not work in the controlled area during pregnancy.

The radiation doses of all employees working in the control area are monitored by means of personal dosimeters.

Isotope U-235 of uranium changes in the reactor into fission products. They are the reason for the strong radiation of spent fuel. Substances that are heavier than uranium are also formed in the fuel, such as plutonium. Otherwise the fuel assembly remains unchanged in size and in practice weighs as much as when loaded in the reactor. Fresh assemblies are shiny, but the oxide layer forming on the surface of the assemblies during the four-year fuel cycle makes them dark.

Fresh fuel is only weakly radioactive. Fresh fuel is delivered to the power plant by ordinary trucks.

The uranium is primarily mined in Canada, Kazakhstan and Australia and manufactured into fuel assemblies in Germany, Sweden and Spain.

The weight of the fuel assemblies used at the plant units in operation (OL1 and OL2) is 280–290 kg and the weight of the assemblies used at OL3 is ca. 780 kg. This weight includes the uranium pellets as well as all the structures of the assembly. The assemblies of the units in operation contain ca. 170–180 kg of uranium each and the assemblies of OL3 ca. 530 kg each.

At Olkiluoto 1 and Olkiluoto 2, each fuel rod contains ca. 400 fuel pellets. The fuel rods of Olkiluoto 3 contain ca. 300 pellets.

Spent fuel from Olkiluoto will be emplaced for final disposal in the final disposal facility to be constructed in Olkiluoto by Posiva Oy for its owners TVO and Fortum. Final disposal is based on the use of multiple release barriers, which guarantee that nuclear waste cannot come into contact with organic nature or anywhere near people. These barriers include the state of the fuel, the final disposal canister, the bentonite buffer, the backfilling of the repository tunnels and the surrounding bedrock. Read more on Posiva's web site.

Even a rich natural uranium deposit is dangerous in terms of radiation. Spent fuel begins to resemble a rich uranium deposit after a few hundreds of thousands of years. The penetrating gamma radiation disappears from spent fuel in a few hundred years. The multiple barrier system used has been designed to guarantee that the spent fuel does not constitute a safety risk to future generations. The final disposal repository will be closed in a way that makes it possible for the normal life of society to go on above the repository. Read more on Posiva's web site.

An earthquake would probably not affect final disposal at all. The final disposal facility is built inside an intact bedrock block and the stresses caused by the movement of the earth's crust will be relieved along existing block boundaries, while the actual block remains intact. Olkiluoto bedrock is stable and about 1800 million years old.

Uranium is quite a common element found everywhere in e.g. bedrock granite. The known uranium resources available for exploitation at reasonable mining costs are sufficient for the needs of the existing reactors for more than 80 years. Considerable amounts of uranium are obtained also as a by-product from e.g. copper and gold mining operations. Seawater constitutes an enormous potential uranium reserve, which so far has not been exploited at all. Phosphates also constitute an extremely large uranium reserve. The use of thorium as a fuel and the development of fast reactors are also realistic alternatives.

The known uranium reserves are adequate to fulfil demand for several hundreds of years. During 1953 – 2003, the total amount of uranium used by all the reactors of the world was about 1.5 million tons. The known and estimated uranium reserves amount to ca. 15 million tons at present.

Uranium only accounts for less than 10 percent of the production costs of nuclear fuel. Consequently, changes in uranium prices have only a small effect on the price of nuclear electricity. The sufficiency of uranium resources will not pose a problem to nuclear power production.



The fuel can be recycled by separating components suited for reuse from the fuel. The amount of high-level waste can be reduced through reprocessing, but its radioactivity cannot be influenced with the methods available at present. Fuel is not being reprocessed in Finland.

By virtue of the Nuclear Energy Act, spent fuel may not be exported and there are no reprocessing facilities in Finland. The price level of reprocessing at present also makes it an uneconomical alternative for Finnish nuclear power plants. The amount of spent fuel generated in Finland is so small that reprocessing is not economically viable.

No. The fuel used in Olkiluoto is uranium oxide.

About 2/3 of the thermal output of the reactor. The same applies to all condensing power plants, such as coal-fired power plants. The efficiency of the power plant is naturally being continuously improved. For example, TVO invested in 2010 and 2011 significantly, about 160 million euro, in upgrades designed to improve the efficiency and safety of the OL1 and OL2 plant units. Improved efficiency means that the share of the output of the plant units released as heat into the sea is smaller than before.

Utilisation would not be lucrative, because Olkiluoto power plant is located far from major population centres and there are no other large clusters of electricity consumers nearby either. Olkiluoto nuclear power plant is designed for large-scale electricity generation, and the production of heat woul´d reduce the production of electricity.

It is the exhaust vent stack of the power plant's ventilation system.

An actual explosion is not possible in a nuclear power plant, because the uranium-235 concentration of the reactor fuel is only 3-4%. A nuclear explosion requires a concentration of more than 90%. The explosions that took place in the Fukushima nuclear power plant accident in Japan as a result of the natural disaster in March 2011 were caused by the accumulation of hydrogen in the top parts of the reactor buildings. This kind of accumulation of hydrogen is prevented at the OL1 and OL2 plant units through technical arrangements. A nitrogen atmosphere prevails in the reactor containment during power operation to prevent hydrogen explosions. The containment is also equipped with permanent systems for controlled combustion of hydrogen released in a potential accident. The generation of hydrogen as a result of the overheating of the spent fuel stored in the pools of the reactor building, as well as possible hydrogen fires are prevented by securing the cooling of the fuel.

Terrorism has been prepared for already in the construction of the power plant units, and in the plant upgrade projects and analyses carried out on the plant units. Safety is assured through both structural and administrative means. The systems responsible for safety are located on different sides of the plant unit, far away from each other. The simultaneous destruction of all of them is unlikely. TVO also has in place a specific corporate security organisation. If necessary, this organisation works in cooperation with public organisations, such as the police, the coast guard, and the defence forces. Information related to security is classified.

The authorities defined in the Rescue Act, such as civil protection, fire and rescue authorities as well as the police are responsible for civil protection in the event of an accident. TVO is under the Nuclear Energy Act obliged to maintain an emergency organisation and to prepare for emergencies at the plant units. TVO is also legally obliged to provide information about the plant status in an emergency. Information to the general public is also provided by the Radiation and Nuclear Safety Authority and e.g. in the channels of the Finnish Broadcasting Company (Yleisradio). The Rescue Act was last amended on 1 July 2011. More specific procedures for nuclear power plant accidents and radiation emergencies were also defined in the amendment. Teollisuuden Voima Oyj organises regular exercises together with authorities to prepare for the highly improbable event of a nuclear power plant accident.

Finnish nuclear power plants are legally obliged to take out nuclear liability insurance to cover damages caused to third parties. The primary responsibility always rests with the plant owner. The secondary responsible party is the State of Finland, and the third instance liable for damages is an association of Finland and other OECD Convention states.

Owing to the massive construction of the nuclear power plant it is improbable that an aircraft crashing into the plant would cause significant damage. The heavy components of the aircraft would most likely only penetrate to the first rooms through the external wall. The systems responsible for plant safety are located on different sides of the plant unit, far away from each other. The simultaneous destruction of all of them is unlikely. The possibility of an aircraft crash has been taken into account already at the design stage of OL3 and the walls of the reactor building will be aircraft crash resistant.

Three severe accidents have taken place in nuclear power plants that produce electricity. The first accident occurred at the Three Mile Island plant in USA in 1979, the second in Chernobyl in Soviet Union in 1986 and the third in Fukushima, Japan, in 2011.

In the Three Mile Island accident, so much cooling water was lost through a safety valve, which stuck in open position that the reactor dried out, over-heated and melted in part. High levels of radioactivity were released inside the plant, but releases to the environment were minor.

The reactor of the Chernobyl nuclear power plant in Soviet Union (now Ukraine) was explosively destroyed in 1986. The complete collapse of the reactor resulted in a major release of radioactivity.

The most recent severe nuclear accident took place at the Fukushima Daichi plant in Japan. The root cause of the accident was an extremely exceptional natural disaster. A high-magnitude earthquake was followed by a tsunami wave, which hit the plant site located on the shore of the Pacific Ocean. The tsunami activated the mechanisms designed for controlled shutdown of the reactor, but due to the loss of off-site power and cooling water, they failed to operate as planned.

The INES scale (International Nuclear Event Scale) is used by the International Atomic Energy Agency (IAEA) for categorisation of nuclear power plant incidents and nuclear accidents to communicate the significance of the events in terms of radiation and nuclear safety.

There are seven INES levels. The level of an incident or accident is determined based on the deterioration of safety or radiation effects on the environment or the plant site. In addition to the seven non-zero levels, there is also level 0, which is applied to incidents with minor significance to radiation or nuclear safety.

The Fukushima and Chernobyl accidents are assigned to level seven and the Three Mile Island accident to level five.











TVO always openly communicates on its web site information both to the media and to the public about any significant disturbances that affect the operation and safety of the power plant. All abnormal events at the plant are reported to the Radiation and Nuclear Safety Authority (STUK), which is the authority that controls the safety of nuclear power plants in Finland. Both TVO and STUK publish an annual report about the most significant events, and STUK also posts every three months a summary of radiation safety on STUK's web site.

Regulations (YVL Guide 1.10 of the Radiation and Nuclear Safety Authority) prohibit permanent residence within ca. one kilometre from the nuclear power plant. The plant site is surrounded by a protective zone extending to a distance of about five kilometres from the facility. Dense settlement and hospitals or facilities inhabited or visited by a considerable number of people are not allowed within the zone. The number of permanent inhabitants should not be in excess of 200. Pursuant to a regulation of the Ministry of the Interior, an emergency planning zone extending to about 20 kilometres from the facility has been defined for the nuclear power plant. The zone shall be covered by detailed rescue plans for public protection drawn up by the authorities.

The company is under regulatory obligation to know the identity of people within the nuclear power plant site.

Fishing is allowed from a boat in the Olkiluoto water area, except for the entrances of the water intake and discharge channels, which are off-limits to fishers. An access permit is required within the power plant site.

Yes, because the fence serves as an alarm system.

One unit produces electricity at an output 880 MW. About 30 MW is needed for the operation of the plant itself.

This is due to historical reasons, among others. The pressurised water reactor was more dominantly studied during the development of commercial plants at the initial stage of nuclear power in the 1960s and 1970s than the boiling water reactor. Pressurised water reactors were built in large series in e.g. France. The OL3 plant unit now under construction in Olkiluoto is a pressurised water reactor in type.

At present (February 2012), 64 reactors are under construction in the world. The climate issue and the concern about the supply reliability of energy have started to create new interest in nuclear power in many countries. The economic competitiveness of nuclear electricity has also improved the position of nuclear power in comparison with other alternatives.

According to the report published by the International Atomic Energy Agency IAEA in August 2011, 60 IAEA member countries have expressed interest in continued use of nuclear power and 24 countries are planning to expand their existing nuclear power programme. At present about 30% of electricity is in the European Union produced with nuclear power. In addition to Finland, a new nuclear power plant unit is under construction in France. In Europe, nuclear power construction projects are being planned also in Slovakia, Bulgaria, Romania, Czech Republic, Hungary, Slovenia, Great Britain and Poland.

Our neighbouring country Sweden has modernised her existing plant units increasing their output and extending their lifespan. According to the new policy adopted in Sweden, construction licences are to be granted again for new plant units to replace the existing reactors. The new units would be built on the existing plant sites.

Ever more efficient equipment and systems have become available through technological advances and with more operating experience gained on nuclear power. This has made significant increases in the turbine efficiency possible at the Olkiluoto plant units. New fuel technology has resulted in more energy being produced by the same amount of fuel.

The increase in output has been planned on the basis of maintaining and improving the high safety level. New advance technology has increased the reliability of the plant, which translates into improved safety.

The upgrade projects implemented in 2010 and 2011 increased the net output of both plant units, OL1 and OL2, by ca. 20 MW. As the plant units are kept in pristine condition at all times, the possibility of further increases in output can be investigated also in the future, when improvements are implemented at the plant units in other respects.

The current perception is that Olkiluoto power plant units 1 and 2 have a further 40 years of service life left. Commercial operation started at Olkiluoto 1 in 1979 and at Olkiluoto 2 in 1982.

The radioactive components of the plant units will be dismantled and placed in the operating waste repository, which is located in Olkiluoto and will be expanded for the dismantling waste. The dismantling is planned to be carried out about 30 years after the units have been shut down. The plans consisting of the cost estimate, the schedule and the work plan have been prepared, and the funds required to cover the costs are being collected in the price of electricity.

There are many reasons. Examples of factors affecting the costs of nuclear electricity include differences in engineering (e.g. an expensive cooling tower or the need for new infrastructure), how much electricity is produced annually, i.e. the capacity factor, differences related to fuel, spent fuel management and the funding procedure and possibly the commitment to expensive reprocessing.

Different estimates of the demand for electricity are presented constantly. According to the estimates, the consumption of electricity will increase despite economic fluctuations. Pursuant to the Year 2008 Climate and Energy Strategy of the Finnish Government, the annual demand for electricity is expected to be ca. 103 terawatt-hours (TWh) in 2020, or if consumption can be reduced through energy efficiency measures, 98 TWh. The starting point of the strategy is to ensure that industrial investments are not restricted due to production capacity.

Finnish Energy Industries and the Confederation of Finnish Industries presented their common estimate of the demand for electricity in 2030. These organisations concluded that provided recovery from the current recession is rapid, the demand for electricity will be 111 TWh in 2030. Slow recovery would result in a consumption of 100 TWh. The rate of increase in the demand for electricity is highest in the service sector and transport. The demand for electricity increases by about 40% in the service sector, and hybrid and electric cars multiply the consumption of electricity in transport. The consumption of electricity for heating may decrease as a result of energy efficiency measures. The demand for electricity in the industry is estimated to increase by 2-16% in comparison with the pre-recession figures.

The energy police studies conducted in the EU in recent years, such as the energy Road Map 2050, indicate that the share of electricity of all energy production will increase despite the improvements made in energy efficiency. In Finland, 16.4% of the consumed electricity was imported electricity in 2011, i.e. the amount of imported electricity increased by more than 30 percent over 2010. Domestic electricity production capacity must be increased to reduce the amount of imported electricity. The growing consumption of electricity must also be covered with electricity produced in Finland.

Reasons for the growing consumption of electricity include e.g. population increase, higher gross national product as well as improved standard of living. The number of electrical appliances in households is still on the increase; heat pumps, for example, are used to replace oil heating. The degree of processing of industrial products also increases, and electricity plays a crucial role in their manufacture. The manufacture of all new products, such as bioproducts, increases the consumption of electricity. The growing demand for services also increases electricity demand.

Electricity must be produced with as low emissions as possible to curb climate change.







Uranium is mined in many countries by many companies. TVO is not involved in mining industry. TVO primarily acquires uranium from Kazakhstan, Australia and Canada. Uranium mining, like all mining activities, is governed by strict environmental regulations. TVO makes visits to the uranium mines to verify that the activities meet the defined objectives in terms of environmental protection and social responsibility.

Nothing. No public funding is required for the construction of the nuclear power plant.

How would the construction of new nuclear power affect the use of renewable energy sources and promotion of energy efficiency? Nuclear power and renewable energy sources do not compete on the same market. Nuclear power is used to produce baseload power for the needs of the society. Biomass is used in cogeneration of electricity and heat, while nuclear power has traditionally been used to produce just electricity. Since the previous decision on a new nuclear power plant was made, the use of bioenergy has increased by 2 percent per year. For example, Pohjolan Voima, which is the largest shareholder in TVO, has together with its cooperation partners invested more than 1.4 billion euro in biofuel-driven plants (1990–2008). This has generated in Finland more than 1100 MW of new electricity production capacity based on bioenergy. Wind power has also benefited from strong development in recent years with a specific programme launched to promote wind power. The companies that own TVO also participate in this programme.

The strategy also lays down ambitious objectives for energy savings. Practical measures are presented in the new energy saving programme. Most of the areas in which savings are to be made are related to heating.



Based on the recent progress reports received from the plant supplier, AREVA-Siemens Consortium, TVO is preparing for the possibility that the start of the regular electricity production of Olkiluoto 3 nuclear power plant unit may be postponed until year 2016.

Like all solutions related to the operation of a nuclear power plant, automation will also be based on several mutually supporting and mutually independent systems. There will be both programmable and hardwired systems at Olkiluoto 3. This guarantees the safety of the plant in all conditions and situations.