Finland generates roughly a third of its electricity from nuclear power, placing it among the most nuclear-reliant countries in Europe. With five operating reactor units, the world’s first deep geological repository for spent fuel under construction, and active research into small modular reactors for urban heating, Finland offers one of the most complete case studies of a country that has committed to nuclear energy across the entire fuel cycle. That commitment has not been without setbacks, cost overruns, or geopolitical shocks, but it remains a defining feature of Finnish energy policy.
Finland’s Operating Reactors
Finland currently operates five commercial nuclear reactors at two sites. The Loviisa plant, on the southern coast, houses two Soviet-designed pressurized water reactors that have been operating since the late 1970s. The Olkiluoto site, on the western coast near the municipality of Eurajoki, hosts two boiling water reactors that came online in the late 1970s and early 1980s, plus the much newer Olkiluoto 3 unit. Together, these plants provide a stable baseload that keeps Finnish electricity prices comparatively low and carbon intensity down.
The country’s low-carbon electricity roadmap has long relied on two pillars: nuclear and wind. A 2022 analysis of Finland’s carbon neutrality target for 2035 noted that increased energy production with reduced emissions was possible mainly because of those two sources.1Energy Strategy Reviews. Sectoral low-carbon roadmaps and the role of forest biomass in Finland’s carbon neutrality 2035 target – Section: 4.1. Energy sector Wind capacity has expanded rapidly in recent years, but nuclear remains the backbone of round-the-clock, weather-independent supply.
Olkiluoto 3 and Europe’s Longest Construction Project
Olkiluoto 3 is a European Pressurized Reactor (EPR) and, at roughly 1,600 megawatts electric, one of the most powerful individual reactor units in the world. It finally began regular electricity production in April 2023, but the path there was painful. Construction started in 2005 with an expected completion around 2009. What followed was a cascade of delays driven by design changes, concrete quality problems, welding issues, and disputes between the utility (TVO), the reactor vendor (Areva, now Framatome), and Siemens. The project ran roughly 14 years behind schedule, and costs ballooned far beyond initial estimates.
Despite those problems, the reactor is now operating and delivers a meaningful share of Finnish electricity. On windy days when Finnish wind farms are also producing at high capacity, the combined output can push Finland into being a net electricity exporter, a position the country historically has not held. For a nation that long depended on electricity imports from its neighbors, that shift matters.
The Hanhikivi 1 Collapse and the Russia Factor
Finland’s energy roadmap once counted on a sixth reactor, Hanhikivi 1, to be built in the northern Ostrobothnia region by a consortium led by Rosatom, Russia’s state nuclear corporation.2Energy Strategy Reviews. Sectoral low-carbon roadmaps and the role of forest biomass in Finland’s carbon neutrality 2035 target – Section: 4.1. Energy sector The project had been controversial from the start, partly because of the Russian ownership stake and partly because of local opposition. But the decisive blow came in 2022, when Russia invaded Ukraine.
Research on Finland’s nuclear policy elite found that the war represented a genuine turning point: the external crisis was intense enough to override the established institutional arrangements that had supported cooperation with Russia on nuclear energy.3Scandinavian Political Studies. The Impact of Three Crises on the Hegemony of Finland’s Nuclear Power Elite The Finnish consortium Fennovoima terminated its contract with Rosatom in May 2022, effectively killing the project. This was not just about sanctions logistics; it reflected a broader reassessment of energy security dependence on Russia, paralleling Finland’s simultaneous decision to apply for NATO membership.
The loss of Hanhikivi 1 left a gap in Finland’s projected nuclear capacity. Whether that gap will eventually be filled by a new large reactor, by small modular reactors, or simply by accelerated wind and solar deployment remains an open and actively debated question in Finnish energy planning.
Onkalo and the Hundred-Thousand-Year Problem
Finland is building the world’s first permanent deep geological repository for high-level nuclear waste, a facility called Onkalo (Finnish for “cave” or “cavity”). Bored into ancient bedrock on the island of Olkiluoto, the repository is engineered to isolate spent fuel for over one hundred thousand years.4ScienceDirect / Elsevier (Energy Research & Social Science). Waiting for waste: Nuclear imagination and the politics of distant futures in Finland That timescale is staggering, longer than modern humans have existed as a species, and it makes every engineering decision at Onkalo an exercise in deep-future thinking.
Planning began in 1983, when Finnish authorities started surveying the country for geologically stable sites. They eventually selected a location in western Finland near the existing Olkiluoto reactors. Parliament debated the project and approved the site by the end of 2001. A joint venture between Finland’s two main nuclear plant operators, called Posiva Oy, received its construction license, and building started in 2012.5ScienceDirect / Elsevier (Energy Research & Social Science). Waiting for waste: Nuclear imagination and the politics of distant futures in Finland The repository uses a multi-barrier concept: spent fuel is sealed in copper-and-iron canisters, surrounded by bentonite clay that swells when wet and self-seals, and placed in tunnels hundreds of meters below the surface in crystalline bedrock that has been geologically stable for nearly two billion years.
Characterizing the groundwater behavior at those depths has been a major part of the site investigation program. Researchers have used surface-based and underground data to model how water moves through the bedrock’s fracture networks, and hydraulic tests in pilot holes have revealed that groundwater flow around the planned repository volumes is extremely low.6ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management, Parts A and B. Characterization of Bedrock Hydrogeology at the Olkiluoto Site Using Surface Based and Underground Data Low flow matters because water is the primary mechanism by which radioactive material could theoretically migrate away from the repository over millennia. The less water moving through the rock, the slower any potential migration.
Onkalo is expected to begin accepting spent fuel in the mid-2020s, making Finland the first country in the world to have a functioning solution for permanent disposal of high-level nuclear waste. Every other nuclear nation is still searching for sites, fighting political battles over location, or stuck in decades-long licensing processes. Finland’s relative success on this front is often attributed to a combination of favorable geology, clear legal frameworks, and a political culture that tends to defer to established technical expertise.7ScienceDirect / Elsevier (Energy Research & Social Science). Waiting for waste: Nuclear imagination and the politics of distant futures in Finland
Why Eurajoki Said Yes
One of the most frequently asked questions about Onkalo is how Finland managed to find a community willing to host a nuclear waste repository when so many other countries have failed at that step. The municipality of Eurajoki, which hosts both the Olkiluoto reactors and the Onkalo site, did not simply accept the project out of civic duty. The process involved negotiation, economic incentives, and a long track record of coexistence with nuclear facilities.
Research into the community dynamics found that trust in the nuclear companies played a decisive role. Local residents’ confidence in the competence and care of the operators was heavily influenced by the Nuclear Energy Act, which provided a well-defined institutional framework that shaped how the companies interacted with the community.8J-STAGE (Journal of Environmental Information Science). Trust in Nuclear Companies and Social Acceptance of a Nuclear Waste Repository in Finland Decades of operating nuclear plants in Eurajoki without major incident had built a baseline of familiarity and trust that communities without that history simply do not have.
Economics also mattered. Municipal finances were a primary concern during the siting negotiations. In 1999, Eurajoki drafted a wish list for the government arguing that the real estate tax rate for a spent fuel repository should be considerably higher than for a nuclear power plant. Within six months, the government proposed legislation applying the higher nuclear-facility tax rate to the repository as well, reducing ambiguity and smoothing the project’s path forward.9Progress in Nuclear Energy. Role of the host communities in final disposal of spent nuclear fuel in Finland and Sweden – Section: 6.2. Eurajoki, Finland Property tax revenue from nuclear facilities is significant for a small municipality and funds local services that residents can see and appreciate, which in turn reinforces the sense that hosting nuclear infrastructure is a net benefit.
This model is not easily exportable. Eurajoki’s acceptance grew from a specific mix of existing familiarity with the nuclear industry, a responsive regulatory process, and tangible financial benefits. Countries attempting to site repositories in communities that have no prior relationship with nuclear power face a fundamentally different challenge.
Life Extension at Loviisa
While Olkiluoto 3 is brand new, Finland’s oldest reactors at Loviisa are aging. The two units were originally licensed for a 30-year operating life. Extending that life required detailed analysis of key components to assess how decades of operation, radiation exposure, and thermal cycling had affected the structures. Engineers focused on five critical components, including the reactor vessel, primary coolant pump, steam generators, the pressurizer, and the steel containment building.10Volume 3: Structural Integrity; Nuclear Engineering Advances; Next Generation Systems; Near Term Deployment and Promotion of Nuclear Energy. The Structural Analysis of the Loviisa Plant Steel Containments for Service Life Extension
For the containment specifically, the analysis combined 30 years of monitoring data with three-dimensional structural modeling that accounted for degradation effects. The goal was to identify the weakest points and estimate how much useful life remained. Based on this work, the plant received approval for a 20-year life extension.11Volume 3: Structural Integrity; Nuclear Engineering Advances; Next Generation Systems; Near Term Deployment and Promotion of Nuclear Energy. The Structural Analysis of the Loviisa Plant Steel Containments for Service Life Extension Life extensions like this are common in the nuclear industry globally, but they require significant investment in inspection, analysis, and sometimes physical upgrades. For Finland, keeping Loviisa running means retaining about 1,000 megawatts of low-carbon baseload capacity that would otherwise need to be replaced.
Small Modular Reactors for District Heating
One of the more distinctive threads in Finnish nuclear planning involves using small modular reactors not just for electricity but for district heating. Finland’s climate makes heating a major energy demand, and Helsinki’s metropolitan area relies on an extensive district heating network. Decarbonizing that network is a significant challenge because much of the heat currently comes from fossil fuels or biomass.
A 2025 feasibility study examined two SMR designs for integration into Helsinki’s district heating and cooling system. One was an academic concept called E-SMR producing both electricity and heat, and the other was the LDR-50, a heating-only reactor developed by VTT, Finland’s Technical Research Centre. Both designs reduced carbon dioxide emissions and enhanced electricity supply in the modeled scenarios. However, the economics diverged sharply: the E-SMR was not a profitable investment under the modeled conditions, while the LDR-50 was.12Nuclear Engineering and Design. Feasibility of small modular reactors for decarbonizing district heating systems: a case study of the Helsinki metropolitan area
The LDR-50 is purpose-built for heat production, operating at low temperatures and pressures compared to conventional reactors. Its smaller size, around 50 megawatts of thermal output, makes it a better fit for modular deployment within urban heating networks. If this concept moves from feasibility studies to actual construction, it would represent a genuinely novel use of nuclear technology, one focused on displacing fossil fuels in heating rather than in electricity generation. Helsinki’s city government has expressed interest, though no construction decisions have been made yet.
Nuclear on the Finnish Grid
Nuclear plants are typically designed to run at constant full power, producing steady baseload electricity. In an energy system increasingly shaped by variable wind and solar output, that inflexibility can become a challenge. Finland’s grid operator Fingrid has noted that as the energy mix evolves, rotating generation from conventional plants will become more limited and price swings could grow.13VTT Technical Research Centre of Finland. Risks of adaptive control of NPP electrical systems and stability of the grid
There have been discussions about whether Finnish nuclear plants could operate more flexibly, ramping output up and down in response to market signals. So far, the consensus has been that other resources handle balancing better. Fingrid has reported that it has never needed to demand that a nuclear plant reduce power or disconnect; market-based solutions have been sufficient.14VTT Technical Research Centre of Finland. Risks of adaptive control of NPP electrical systems and stability of the grid In practice, Finnish nuclear plants run flat out and the system accommodates variability through hydropower imports from the Nordics, demand response, and curtailment of wind generation during oversupply periods. Whether that balance holds as wind capacity continues to grow is an open question.
The Cost Debate
The economic case for nuclear power in Finland is genuinely contested. The Olkiluoto 3 experience shook confidence in the ability to deliver large reactor projects on budget, and the cancellation of Hanhikivi 1 removed the possibility of a second attempt with a different vendor. Against that backdrop, researchers have begun modeling what a heavy nuclear expansion would cost Finland compared to a renewables-dominated path.
A 2025 study modeled several scenarios in which Finland tripled its nuclear capacity to about 13.2 gigawatts by 2050, using various combinations of large and small reactors alongside nuclear combined heat and power. These nuclear-heavy scenarios were compared to a reference scenario that optimized freely for zero emissions. The nuclear expansion scenarios showed annualized system costs roughly 71 to 84 percent higher than the renewables-based alternative, coming in at around 18.4 to 19.7 billion euros per year compared to about 10.7 billion euros for the renewables path.15ScienceDirect / Elsevier (Energy). Who will foot the bill? The opportunity cost of prioritising nuclear power over renewable energy for the case of Finland
Those numbers are striking, but they come with caveats that the headline figure does not capture. Cost-optimization models depend heavily on assumptions about future technology costs, financing rates, construction timelines, and system flexibility. Nuclear advocates argue that such models tend to undercount the system integration costs of high-renewable grids, including transmission upgrades, storage requirements, and backup capacity for windless winter weeks, which Finland certainly has. Renewables advocates counter that nuclear cost overruns are the norm, not the exception, and that solar and wind costs have fallen faster than anyone predicted. The honest reading of the evidence is that massive nuclear expansion in Finland would be expensive, but the precise cost gap depends on assumptions that reasonable people disagree about.
Nuclear Heating and the Finnish Winter
Something that often surprises outside observers is how much of Finland’s total energy demand goes to heating rather than electricity. Finnish winters are long, dark, and cold, with temperatures in the south regularly dropping below minus 20 degrees Celsius and staying there for weeks. District heating networks in Finnish cities are not optional infrastructure; they are essential to keeping buildings habitable. Decarbonizing these networks is arguably as important to Finland’s climate goals as decarbonizing electricity, and arguably harder.
Most district heating today comes from a mix of natural gas, biomass, coal (being phased out), and waste incineration. Heat pumps are growing but face efficiency limits in extreme cold. This is where the nuclear heating concept gains traction: a reactor produces steady, reliable thermal energy regardless of outdoor temperature or cloud cover. The LDR-50 concept studied for Helsinki is specifically designed for this purpose, operating at temperatures well suited to feeding hot water into a district heating network without the complexity or safety envelope of a full power reactor.16Nuclear Engineering and Design. Feasibility of small modular reactors for decarbonizing district heating systems: a case study of the Helsinki metropolitan area
If Finland eventually builds a fleet of heating reactors for its largest cities, it would be breaking genuinely new ground. Nuclear power has been used for district heating in a handful of places historically, but nowhere has it been deployed as the primary heat source for a major metropolitan area. Finland’s combination of extreme climate, well-developed district heating infrastructure, and institutional comfort with nuclear technology makes it one of the few places where the idea has a realistic chance of moving beyond studies and into steel and concrete.