FAQ

Posiva Oy is a Finnish company that manages the final disposal of the spent nuclear fuel of its owners Teollisuuden Voima Oyj (TVO) and Fortum Power and Heat Oy (Fortum).

Posiva is designing and constructing the world’s first disposal facility for spent nuclear fuel in Finland. It will also operate and eventually close the facility. The company aims to ensure that spent nuclear fuel is safely isolated from people and the environment over a very long period.

Posiva was established in 1995 to manage the final disposal of its owner companies’ spent nuclear fuel. In practice, Posiva will manage the final disposal of all of the nuclear fuel spent in Finland, as the owner companies TVO and Fortum are the operators of all the five nuclear power plant units operating in Finland.

According to the Finnish Nuclear Energy Act, nuclear power companies themselves are responsible for their nuclear waste management. Posiva’s mission is to implement this responsibility safely over the long term and based on research.

Spent nuclear fuel has been used inside a nuclear reactor for electricity generation. It is removed from the reactor once it can no longer be efficiently utilised for energy production at the current Finnish nuclear power plants.

Inside the reactor, some of the uranium in the fuel converts into fission products, and new elements, such as Plutonium, form in the fuel. As a result, spent nuclear fuel is highly radioactive and will generate heat for a long time. In practice, however, fuel assembles will maintain their shape and weight as they are used – only their appearance changes slightly, as a spent fuel assembly will have a dark oxide layer on its surface.

In Finland, spent nuclear fuel is first transferred to an interim storage facility at the power plant, where it will cool down for several decades. Then, it will undergo encapsulation and safe final disposal deep inside the Olkiluoto bedrock. Although it would be technically possible to reprocess spent nuclear fuel, Finland has decided on direct disposal as the final disposal solution.

Spent nuclear fuel still contains radioactive materials that must be kept isolated from people and the environment for a long time. Finland has decided on final disposal deep in stable bedrock, which is estimated to be a safe and responsible way of managing spent nuclear fuel over a very long period.

This is not a temporary storage solution; it is literally ‘final’.

In Finland, the current generation carries the responsibility for the management of spent nuclear fuel instead of leaving it to future generations.

According to the Finnish Nuclear Energy Act, the spent nuclear fuel generated in Finland must be managed in Finland. Spent nuclear fuel may not be taken permanently abroad for final disposal, and no spent nuclear fuel from other countries may be imported to Finland for final disposal.

This is based on an internationally widely accepted principle, according to which each country is itself responsible for its nuclear waste management. This decision increases safety, clarifies responsibilities and ensures that the consequences of nuclear energy use are managed where they occur.

Posiva’s disposal facility has been designed exclusively for the spent nuclear fuel generated in Finland by Teollisuuden Voima Oyj and Fortum Power and Heat Oy.

No. The spent nuclear fuel will remain the property of the nuclear power companies that generated it. Posiva is responsible for the safe final disposal of the fuel under assignment from its owners.

No. Posiva neither generates electricity nor operates nuclear power plants. Its mission is to manage the final disposal of spent nuclear fuel.

No. Posiva’s disposal facility is only intended for the spent nuclear fuel generated in Finland by TVO and Fortum. The Finnish law states that no spent nuclear fuel from other countries may be brought to Finland for final disposal.

Posiva accepts spent nuclear fuel from Teollisuuden Voima’s nuclear power plant at Olkiluoto and Fortum’s nuclear power plant in Loviisa. They comprise a total of five nuclear power plant units: three at Olkiluoto (Olkiluoto 1, Olkiluoto 2 and Olkiluoto 3) and two in Loviisa (Loviisa 1 and Loviisa 2).

The fuel spent at each plant unit is taken from the power plant’s interim storage to the encapsulation plant before it is placed in final disposal.
At that point, the spent fuel is considerably less radioactive than when its use in electricity production had just stopped. For example, the radiation level of the first fuel from Olkiluoto to be placed in final disposal will have dropped to approximately one thousandth.

Posiva’s disposal facility has been designed to receive approximately 6,500 tonnes of spent nuclear fuel generated in the Finnish nuclear power plants of Teollisuuden Voima Oyj and Fortum Power and Heat Oy according to their current operation and licensing assumptions.

Final disposal operations will take place over the course of several decades, as spent nuclear fuel is taken from the power plants’ interim storage to encapsulation and further to final disposal.

The total quantity of the spent nuclear fuel placed in final disposal is based on the spent nuclear fuel generated at the owner companies’ nuclear power plants during their service life. Decisions that change the plants’ service life or operating licences may impact this total quantity of fuel.

Of all the radioactive waste generated at nuclear power plants, spent nuclear fuel has the highest level of radioactivity. However, the plants also generate low- and medium-level radioactive waste. Low-level waste includes items such as protective equipment used during maintenance and machine parts removed from the plant. Medium-level waste is generated during the cleaning of the process water, for example.

There are long-established practices for the final disposal of such waste in Finland. At Olkiluoto, low- and medium-level operating waste has been disposed of since 1992 in the VLJ repository constructed in bedrock. In Loviisa, such waste has been placed in a separate repository since 1998.

In contrast, Posiva is tasked with the final disposal of spent nuclear fuel generated by TVO and Fortum. The operations beginning at ONKALO mean the start of the final disposal of the most active kind of nuclear waste which is managed over the longest term.

ONKALO® is Posiva’s disposal facility at Olkiluoto. It comprises the above-ground encapsulation plant and the underground disposal repository, where spent nuclear fuel will be placed in final disposal in stable bedrock at a depth of approximately 430 metres.

ONKALO was originally built as an underground research facility for confirming that the Olkiluoto bedrock is suitable for final disposal. Over the years, the concept has expanded in Finland as well as internationally to cover Posiva’s entire disposal facility. The deepest parts of ONKALO extend to approximately 455 metres underground.

Nowadays, the two have no significant difference.

ONKALO originally referred to the underground research facility for studying the Olkiluoto bedrock and developing the final disposal solution. Since then, the concept of ONKALO has expanded to cover Posiva’s entire disposal facility, which comprises the overground encapsulation plant and the underground disposal repository.

In the disposal facility, spent nuclear fuel is first encapsulated inside canisters on the surface, and then the canisters are taken underground for final disposal. The actual disposal repository is located at a depth of approximately 430 metres.

ONKALO is the name that Posiva has given to the disposal facility. It comes from the Finnish word “onkalo”, meaning a cavity that occurs naturally or is created in rock. It is a fitting name for the underground disposal repository located deep in the Olkiluoto bedrock.

ONKALO is written in all uppercase, because it is a proper name that Posiva has registered. Over the years, it has expanded internationally to refer to the world’s first final disposal plant for spent nuclear fuel.

Final disposal will be carried out at a depth of approximately 430 metres in the Olkiluoto bedrock.

At this depth, the rock is stable, groundwater conditions are favourable and natural phenomena that occur on the surface have little impact. For these reasons, a depth of slightly more than 400 metres is considered to offer the best prerequisites for long-term safety.

The disposal facility comprises the overground encapsulation plant and the extensive ONKALO® system of underground facilities; in addition to the actual deposition tunnels, it covers the central tunnels, a driving tunnel and technical facilities.

The building for the above-ground encapsulation plant was completed in 2022. It was handed over to Posiva for nuclear equipment installations in May 2022. The building has a floor area of approximately 11,500 m2 and its volume is approximately 70,000 m3. The completion of the building was followed by the installation, commissioning and test operation of the process systems that are needed for final disposal.

This has also progressed well: the trial run of final disposal for the encapsulation plant was completed in early 2025. The test operation involved testing the entire encapsulation process without actual spent nuclear fuel.

The construction of the underground disposal repository will gradually continue throughout the final disposal operations. This means that all the deposition tunnels are not excavated in advance; rather, new tunnels and deposition holes are built as they are needed. This way, the design and construction of future facilities will always be able to leverage the latest research and experience gained over the course of operations.

Once ONKALO® is fully completed, it will encompass approximately 50 kilometres of tunnels, and the disposal repository will extend over an area of approximately 2 km2. The disposal repository is located more than 400 metres underground.

In Finland, the development of a final disposal solution for spent nuclear fuel has been going on for more than 40 years.

Analyses on the safe final disposal of spent nuclear fuel were started already in the 1970s. In 1983, the Finnish Government approved the programme in principle for nuclear waste management, which outlined the final disposal and its schedule targets. 

At the same time, nuclear power companies were issued an obligation to manage the spent nuclear fuel that is generated as a result of using nuclear energy. This launched systematic research and development efforts towards implementing a safe final disposal solution.

Over the decades, the work has gradually progressed from geological surveys to deciding the final disposal site, construction of ONKALO, development of the final disposal method and construction of the encapsulation plant and disposal facility. The entire development process has been based on research, gradual progress and independent regulatory oversight.

In 1995, Teollisuuden Voima and Imatran Voima – the predecessor of the current Fortum – established Posiva Oy to manage the final disposal of the companies’ spent nuclear fuel. Posiva’s operations were officially started at the beginning of 1996.

The final disposal operations will proceed gradually over the course of several decades, as spent nuclear fuel is generated at the Olkiluoto and Loviisa nuclear power plants. Based on the current operating and licensing assumptions, it is estimated that the final disposal operations will continue long into the 22nd century.

Spent nuclear fuel is first placed in interim storage at nuclear power plants where it cools down for several decades. As final disposal operations are started, spent fuel is gradually brought from these interim storage facilities to Posiva’s encapsulation plant, where it undergoes encapsulation before final disposal in the Olkiluoto bedrock.

Final disposal is a process that advances gradually. Spent nuclear fuel is encapsulated and placed in final disposal as it is transferred from the nuclear power plants’ interim storage facilities to Posiva for processing. Deposition tunnels and deposition holes are also constructed in stages.
Once all the spent nuclear fuel has been placed in final disposal, the deposition tunnels are backfilled and closed as planned. From this point onward, the safety of the final disposal will be based on a passive multi-barrier system.

The disposal facility’s operating licence is granted by the Finnish Government.

Its decision-making is based, among other things, on STUK’s safety assessment, statements from other authorities and documents related to the processing of the operating licence.

The Radiation and Nuclear Safety Authority (STUK) is the Finnish regulatory authority for nuclear safety. It assesses the safety of the disposal facility, supervises Posiva’s operations and oversees the operation of the facility throughout the course of its operations.

Final disposal may only be started after the Finnish Government grants Posiva an operating licence for operating the disposal facility.

However, this does not mean that the operations will start immediately once the operating licence has been granted. Before starting final disposal, Posiva will complete the facility’s commissioning, perform the final tests, verify the necessary approvals with the authorities and obtain permission from STUK to start the operations. All of this will still take some time, but, in the nuclear industry, safety always has priority over the schedule.

The exact time cannot yet be confirmed because it depends on the operating licence process as well as the progress with the final stages of commissioning.

Our aim is to achieve readiness for starting final disposal at the end of 2026, so that we can invite STUK to inspect it

Final disposal will advance gradually over the course of several decades. At the start of operations, approximately 30 to 40 canisters will be placed in final disposal each year, and it is estimated that this could later increase to approximately 60 canisters per year.

Final disposal will advance depending on the accumulation of spent nuclear fuel, the facility’s operating situation and the progress of overall final disposal operations. The operations are planned such that final disposal can be implemented in a safe and managed way throughout the facility’s service life.

Spent fuel is brought from interim storage to the encapsulation plant. There, the fuel assemblies are dried and placed in a copper canister with a cast-iron insert. The canister is closed, its copper lid is welded shut and the integrity of the weld is inspected.

The finished canister is transferred with a canister lift to ONKALO, approximately 430 metres underground. It is taken to a deposition tunnel and lowered into a deposition hole drilled in bedrock. Bentonite clay is placed around the canister. Here, bentonite is used because, among other things, it expands in contact with moisture and forms a tight protective layer around the canister.

Once all the canisters assigned to the tunnel have been placed in final disposal, the tunnel is backfilled and closed according to plan. New deposition tunnels are constructed as the final disposal progresses. Approximately 50 kilometres of new tunnels will be excavated underground during the facility’s operations.

The following animations describe Posiva’s operations in detail:

Posiva animation of the Encapsulation plant

Posiva animation of The Final Disposal of Spent Nuclear Fuel

Yes. In the event that a deviation that impacts safety were to be identified in Posiva’s operations, it is possible to suspend final disposal in order to resolve the situation before resuming operations. Safety has the utmost priority in Posiva’s operations.

The disposal facility will operate for as long as spent nuclear fuel is generated at the owner companies’ nuclear power plants. For example, the newest Finnish nuclear power plant unit, Olkiluoto 3, has a planned service life of at least 60 years, and spent nuclear fuel is cooled for several decades in interim storage before it is placed in final disposal. In practice, the disposal facility will operate well into the 22nd century.

Once all the spent nuclear fuel has been placed in final disposal, the deposition tunnels are backfilled and closed as planned.

Posiva’s final disposal solution has been researched and developed for several decades in Finland as well as internationally. The safety of the solution has been demonstrated through extensive studies, long-term safety analyses and reports required by the authority.

In terms of overall safety, an essential piece is the favourable safety assessment that the Radiation and Nuclear Safety Authority (STUK) issued in August 2026. It lays the central foundation for the later Government decision on the operating licence.

The safety of final disposal is based on the “multi-barrier principle”. Spent nuclear fuel, canisters’ cast-iron insert and copper shell, bentonite clay and solid bedrock create individual barriers that complement one another, thereby preventing radioactive materials from reaching the living environment.

The radioactivity of spent nuclear fuel reduces over time. The radioactive materials with the strongest radiation decay relatively quickly, which is why the fuel’s radiation level decreases significantly during the first decades and centuries.

However, some radioactive materials persist for a long time. After a few hundred thousand years, the radiation properties of spent nuclear fuel start to be comparable, in terms of magnitude, to naturally occurring rich uranium ore. Therefore, the safety of final disposal is estimated over a time span of approximately one million years.

The safety of Posiva’s final disposal solution is based on multiple release barriers that isolate the radioactive materials from people and the environment for the entire time that they could cause significant harm.

The multi-barrier principle means that the safety of final disposal is not based on a single structure or material but on multiple, consecutive barriers that complement one another. Should the performance of one barrier degrade over time, the remaining barriers would still ensure safety.

The barriers in Posiva’s solution include the spent nuclear fuel, canister’s cast-iron insert and copper shell, bentonite clay and more than 400 metres of bedrock. Together, they isolate the spent nuclear fuel from the living environment for a long time.

Copper can withstand the final disposal conditions very well, and it corrodes very slowly in the oxygen-starved groundwater. Furthermore, historical and archaeological copper items have provided experience on how copper behaves over thousands of years.

The final disposal canister comprises a cast-iron insert as well as a copper outer shell.

Cast-iron supports the spent nuclear fuel inside the canister and provides the canister with the necessary mechanical durability. It is designed to withstand the loads it is subjected to under final disposal conditions.

The final disposal canister is surrounded with bentonite, which is a type of natural clay.

This type of clay was chosen because it swells in contact with water, thereby forming a tight protective layer around the canister. In other words, bentonite protects the canister inside the deposition hole and slows down any water flow that might occur.

The safety of final disposal is not reliant on any single structure. This is the core idea behind the multi-barrier principle.

Should the performance of one release barrier degrade over time, the remaining barriers would still isolate the radioactive materials from the environment.

The canister’s copper outer shell acts as a corrosion barrier, whereas the cast-iron insert provides a load-bearing structure for the canister. At the encapsulation plant, the lid of the copper canister is welded tightly shut, and each final disposal canister undergoes a careful inspection before final disposal.

However, long-term safety is not only based on the canister maintaining its integrity. The foundation for Posiva’s final disposal solution is the multi-barrier principle, where several release barriers complement each other.

Safety assessments also consider scenarios in which an individual canister becomes damaged for some reason. The bentonite buffer that surrounds the canister protects it from small rock movements, and if the canister is damaged, the buffer limits and slows down the release of radionuclides. The ceramic form of the spent fuel also acts as a release barrier in itself: uranium is a solid material that dissolves poorly in water, which slows down the release of radioactive materials.

Moreover, the bedrock physically separates the spent fuel from the biosphere and provides stable and predictable conditions for the engineered release barriers.

While the future is difficult to accurately predict, natural phenomena can be studied and modelled.

Posiva’s safety assessment is based on geological studies, laboratory tests, natural history, modelling and international research data. Over the years, there have been assessments on aspects such as glacial periods, land upheaval, erosion and the behaviour of groundwater.

Posiva submitted its safety assessment to STUK for review in late 2021, and the authority issued its assessment in August 2026. There was a lot of material to go through, as the final safety assessment had almost 20,000 pages.

The geology of Finland tells us that there have been several glacial periods in the past, and new glacial periods are expected to occur in the future.

Posiva’s safety case has analysed the safety of final disposal over a time span of up to a million years. The assessments have examined how, for instance, future glacial periods, stress from continental glaciers, permafrost, earthquakes and changes in groundwater and climate affect the final disposal solution.

The final disposal canisters are placed at a depth of approximately 430 metres in the stable Olkiluoto bedrock, which is roughly 1.9 billion years old. The final disposal is based on the multi-barrier principle, where the bedrock, bentonite clay and copper canister all complement the protection provided by each barrier.

Finland is located in a geologically stable area where strong earthquakes are very uncommon. However, Posiva’s safety assessments have also considered earthquakes.

The facilities of the disposal repository are positioned in stable bedrock, avoiding known fracture and fault zones, and the final disposal is based on the multi-barrier principle where the rock, bentonite clay and copper canister ensure safety even in the event of possible earthquakes.

The final disposal site was chosen on the basis of decades of research. At the beginning, more than a hundred potential areas were identified across Finland. The options were gradually narrowed down to five and eventually four sites where detailed studies were undertaken. Several areas would have been suitable for final disposal in terms of their geology, but Olkiluoto proved to be the best choice in the overall assessment.

The Olkiluoto bedrock is stable, well known and suitable for final disposal. In addition, activities relating to nuclear energy have been taking place in the area for decades and, as a result, its geology, environment and conditions are exceptionally well known. Other aspects considered in the site selection included transports of spent nuclear fuel, existing infrastructure and local acceptability.

Since the majority of the spent nuclear fuel generated in Finland comes from the Olkiluoto nuclear power plant, its final disposal in Olkiluoto is also logistically appropriate, as it minimises the need for transports.

Stable bedrock acts as one release barrier in the final disposal.

When canisters are placed in final disposal, they are covered by more than 400 metres of Finnish rock. The Olkiluoto bedrock is nearly 1.9 billion years old and very stable geologically. It protects the final disposal canisters from external impacts and slows down the travel of possible radioactive materials very effectively. While the properties of the bedrock are an essential component in the long-term safety of final disposal, bedrock is still only one of the many release barriers that contribute to the multi-barrier principle.

The safety case refers to extensive documentation that demonstrates the safety of final disposal. It is based on research data collected over several decades, measurements, analyses and modelling.

The essential purpose of the safety case is to demonstrate that spent nuclear fuel will remain isolated from people and living nature and that it will not result in unacceptable harm even in the long term.

Among other things, the safety case examines the final disposal site’s bedrock and groundwater conditions, the performance of the engineered release barriers and various possible future developments even up to the next one million years. The assessments also consider very rare events, such as earthquakes, or conditions that are expected after a very long time, such as glacial periods.

The safety case is used for assessing the disposal facility’s safety during its operation and, in particular, its long-term safety after the end of the final disposal operations and the closure of the facilities.

While Posiva’s safety case and STUK’s safety assessment are closely related, they are two different things.

The safety case means Posiva’s extensive documentation, based on research, measurements, analyses and modelling, which Posiva uses to demonstrate the long-term safety of final disposal. It makes up an essential part of the safety documentation for the operating licence application.

In contrast, STUK’s safety assessment is the authority’s assessment on whether Posiva’s final disposal solution, safety case and the other documentation included in the operating licence application meet their safety requirements.

In practice, Posiva has justified and demonstrated that its solution is safe, whereas STUK has issued the radiation safety authority’s assessment on whether the justifications are sufficient and safety requirements are met.

The matter was resolved on 4 August 2026 when STUK published its safety assessment on the operating licence application and issued a favourable safety statement on the operating licence application to the Ministry of Economic Affairs and Employment.

However, STUK’s favourable safety assessment does not mean that the safety case is now done and dealt with. The safety case will be updated and specified further during the later stages of final disposal based on new insights, operating experience and the authorities’ requirements at 10 year intervals at the minimum.

The safety case is not a one-time assessment; it is maintained and updated at the different stages of final disposal according to authorities’ requirements. According to the new Finnish Nuclear Energy Act, the safety case must be updated at least every 10 years.

Updating the periodic safety assessment is part of the normal process of continuous safety assessment. Among other things, the updates will consider the latest research data, new measurement and monitoring data from the final disposal site, operating experience, technological advancements and the observations made during the construction of the facility and disposal repository. The safety analyses and their underlying models are also specified further as needed.

This way, the safety case evolves alongside the project and is always based on the best available information. The authority reviews the safety case as part of the disposal facility’s licensing and supervision.

Spent nuclear fuel is transported from nuclear power plants’ interim storage facilities to the encapsulation plant at Olkiluoto by using purpose-built and approved vehicles and transport containers. The containers are designed to protect the fuel and the environment during transport.

At Olkiluoto, spent fuel is transferred inside a special transport container just a few kilometres from TVO’s interim storage to Posiva’s encapsulation plant. Inside the encapsulation plant, the fuel assemblies are moved from the transport container to the final disposal canister.
Transports of spent fuel from the Loviisa nuclear power plant to Olkiluoto will begin later. The mode of transport has not been decided on yet, and the possible options are road, rail and sea transport. The detailed transport arrangements will be separately evaluated and approved before starting the transports.

All transports will follow carefully planned procedures as well as the safety and security arrangements required for the transports of radioactive materials.

Cooling reduces the fuel’s radiation level as well as its temperature. Additionally, a sufficiently long interim storage period enables the safe handling, encapsulation and final disposal of the fuel.

It is true that it is technically possible to reprocess or “recycle” spent nuclear fuel. It is possible to extract reusable substances from the fuel, and some countries do this.

Finland, however, has chosen direct final disposal. There are no reprocessing facilities in Finland, and the current Finnish Nuclear Energy Act even prohibits transporting spent fuel abroad for reprocessing. The quantity of spent fuel generated in Finland is so low that it would not be financially viable to construct and operate a reprocessing facility in Finland at the current cost level.

Furthermore, reprocessing would not completely eliminate the need for final disposal. Reprocessing can lower the amount of highly radioactive waste and recover some of the material for reuse, but the remaining highly active waste must be kept isolated for a long time.

Launching the fuel into space would involve significant safety-related and technological risks. A carrier rocket failure, for example, could lead to severe consequences. Final disposal deep in the bedrock is a safer and more reliable solution.

International agreements prohibit the ocean dumping of radioactive waste. Although water does block radiation effectively – and this is exactly why spent nuclear fuel is stored in pools of water at nuclear power plants – water alone cannot be considered to be a release barrier in the long term.

The objective of final disposal is not only blocking radiation but also isolating the radioactive materials from people and the environment for a very long time. Final disposal constructed deep underground in stable bedrock provides a controlled multi-barrier system where the canister, bentonite and bedrock complement each other’s protection.

The design of the final disposal system takes into account the retrievability of the fuel in the event that the global situation changes somehow. This has been considered in Posiva’s original safety principles and assessments by the authorities.

Posiva’s disposal facility is designed for approximately 6,500 tonnes of uranium as spent nuclear fuel.
Posiva’s design documentation estimates that this corresponds to approximately 3,300 final disposal canisters.

However, the exact number of canisters depends on how much spent fuel is generated during the service life of the plants and how the fuel elements can be placed in the canisters. Deposition tunnels are constructed gradually as required.

No.

Final disposal canisters do not contain any explosive materials, and conditions that could cause an explosion will not occur during final disposal operations.

No. It does not contain anything flammable.

The spent nuclear fuel is sealed inside a tight final disposal canister, and the disposal repository does not have the conditions required for combustion.

Like all construction and industrial operations, final disposal has environmental impacts. They occur, for example, as a result of the excavation and construction of underground facilities, and Posiva aims to prevent and mitigate impacts throughout its operations.

The potential radiation impacts to people and the environment are assessed with particular care. The spent fuel is placed deep underground in bedrock and isolated with multiple release barriers, and safety is assessed over very long periods.

The environment at Olkiluoto has been studied since the 1970s. Radiation and impacts on water bodies in the area are tracked among other parameters, and the monitoring of the state of the environment will continue during the final disposal process up until the closure of the facility.

Posiva constantly monitors the state of the environment according to programmes that have been approved by the authorities. Among other things, the monitoring comprises groundwater, surface water and seawater, nature, radiation and other environmental factors. The results are used for ensuring that the operations meet the set requirements.

The start of final disposal operations will not introduce any significant changes compared to the present situation. The state of the environment at Olkiluoto has been systematically tracked since the 1970s when the production of nuclear electricity first started there.

The final disposal solution is designed to prevent the release of radioactive materials into the groundwater. Accordingly, the behaviour of groundwater is one of the key elements in safety assessments.

The behaviour of groundwater as well as the ecosystems at Olkiluoto and in its surroundings have been examined for several decades as part of the assessment of long-term safety, and their monitoring will continue during the facility’s operation.

The safety assessments indicate that final disposal will not have negative impacts on natural organisms.

The environmental impacts are regularly monitored in order to ensure the preservation of the natural state during operations.

The disposal facility’s normal operation will only cause insignificant radiation exposure to the environment or population in the nearby areas. The plant is designed and operated such that environmental releases of radioactive materials will be nearly nonexistent and the resulting radiation doses will remain clearly below the regulatory limits.

The normal operation of the handling and storage of nuclear waste is subject to an annual radiation dose limit of 0.01 millisievert. For comparison, the average Finn receives a dose of approximately 5.9 millisievert per year from all other radiation sources.

However, it is essential to note that 0.01 mSv is the limit and not an estimate of the actual dose that Posiva’s facility would cause. The facility's design is based on the principle of maintaining exposure as low as practically achievable.

Furthermore, the facility’s operations and the radiation levels in the environment are monitored throughout the course of the facility’s operations. At Olkiluoto, the state of the environment and its radiation levels have been studied for decades. As a result, the area’s natural baseline is well understood, which makes tracking changes possible. In addition, STUK will continue to supervise Posiva’s operations and the facility’s radiation safety after the granting of the operating licence throughout the facility’s service life.

The producers of the spent nuclear fuel, that is, Teollisuuden Voima Oyj and Fortum Power and Heat Oy, are responsible for the costs of final disposal.

In Finland, preparing for final disposal is required by law. Nuclear power companies bear the costs of nuclear waste management, and they prepare for future costs through the Nuclear Waste Management Fund. The Fund is managed by the Finnish state.

Posiva’s operations throughout its life cycle are entirely funded by its owner companies TVO and Fortum, not by taxpayers.

No. The principle is that the current generation is responsible for its spent nuclear fuel.

The Finnish system for funding nuclear waste management is built according to this principle to ensure that the necessary funds are collected from the producers of the spent nuclear fuel, Teollisuuden Voima and Fortum, already during the operation of the nuclear power plants.

Overall, the costs for nuclear waste management and final disposal will amount to approximately €6 billion over their life cycle. This figure includes decades of research and development, the construction of the facilities, the extended operating stage and, eventually, the closure of the facility.

Posiva’s operations are funded by its owner companies TVO and Fortum, which have prepared for the upcoming costs via the National Nuclear Waste Management Fund.

Successful final disposal of spent nuclear fuel requires trust and good dialogue between the licensee and the municipality.Posiva’s project has involved hearings, public events and other situations during which residents, decision-makers and other stakeholders have had the opportunity to receive information, ask questions and voice their views.

The goal has been to offer information openly, to listen to different opinions and also to deal with concerns and critical questions. Local participation has involved continuous interaction, and it is part of the project’s statutory decision-making.

The participation of local residents and municipalities has been an important part of the final disposal project since the selection of the final disposal site. Before the site was selected, an extensive environmental impact assessment (EIA) process was completed in 1997–1999, examining four alternative final disposal sites: Eurajoki, Loviisa, Kuhmo and Äänekoski. Local interaction was an essential part of the process, and residents had the opportunity to give feedback on the project and its impacts.

However, the influence of local people was not only limited to hearings. According to the nuclear energy legislation, the Finnish Government could issue a favourable decision-in-principle only if the target municipality was in favour of the project. In practice, municipalities had the opportunity to prevent the construction of the disposal facility on their land. In 2000, the Eurajoki municipal council voted 20 to 7 in favour of choosing Olkiluoto as the final disposal site.

Once all the spent nuclear fuel generated at Posiva’s owner companies’ nuclear power plants has been placed in final disposal, the underground tunnels are backfilled and closed as planned.

After this, the final disposal will be based on passive safety, which does not have to be upheld with continuous maintenance or monitoring.

A final disposal solution for spent nuclear fuel has been extensively developed in Finland for more than 40 years. The project has advanced on the basis of consistent legislation and decision-making, extensive research and development, clear division of responsibilities and independent regulatory oversight.

An essential aspect has been that the technology, legislation, safety requirements and social acceptance have all been worked on in parallel. Nuclear power companies have had a clear responsibility for the spent fuel and the costs of its final disposal. The authorities have had independent oversight of the project. Local municipalities, residents and other stakeholders have also been involved in the process from an early stage.

Furthermore, Finland has been able to hold on to the long-term goal across different governments and generations. In other words, it is not about Finland having some special technology that other countries do not know of. Instead, the solution has been moved forward with determination one step at a time, and the safety of each step has been demonstrated before moving on to the next.

Posiva’s ONKALO is the world’s first industrial-scale disposal facility for spent nuclear fuel. As many other countries are currently developing their own final disposal solutions, Posiva’s pioneering experience and research results have attracted a great deal of international interest.

Yes.

Each year, researchers, authorities, decision-makers, students and media representatives from around the world visit Posiva to learn about the final disposal solution and ONKALO.

The basic principles of final disposal, such as the multi-barrier principle, can be applied elsewhere in the world as well.

However, each country must design its own solution that fits its geology, legislation and nuclear waste management.

No. Posiva is tasked with the final disposal of spent nuclear fuel generated in Finland by its owner companies TVO and Fortum. The Finnish law prohibits importing spent nuclear fuel from abroad for final disposal.

However, Finnish expertise can be utilised elsewhere in the world. Posiva Solutions was established in 2016 for offering international expert services that are based on the competences that Posiva has developed during the final disposal project. So, while competence can be exported, spent nuclear fuel cannot be imported to Finland for final disposal.

Safe final disposal completes the responsible management of the life cycle of nuclear energy: rather than ending with electricity generation, the responsibilities extend to the management of spent fuel. The Finnish pioneering position in final disposal is significant for the entire nuclear industry.

The final disposal solution also matters in terms of nuclear power investments. The EU’s classification system for sustainable financing, the EU taxonomy, sets strict conditions for classifying investments as environmentally sustainable. These conditions also apply to the responsible management of spent nuclear fuel and radioactive waste. Among other things, an EU member state must have a detailed plan for commissioning a disposal facility for highly radioactive waste no later than in 2050. The inclusion of nuclear power in the EU taxonomy improves and diversifies the availability of funding for investments.

Posiva’s most important mission is to ensure that its owners’ spent nuclear fuel can be placed safely in final disposal now and in the future.

All of Posiva’s activities are guided by safety, responsibility, decision-making based on research and continuous improvement.

Posiva Oy’s final disposal operations are not normal market-based business operations that aim to attract as many customers as possible. Posiva’s mission is to implement the statutory responsibility for nuclear waste management of its owners, TVO and Fortum, and the owners finance Posiva’s operations.

However, the expertise developed in Finland over more than 40 years has become commercially valuable. Posiva’s subsidiary Posiva Solutions sells expertise and consulting services in the field of final disposal to foreign nuclear waste management organisations. The company already has approximately 60 customers in 19 different countries.