Finland is set to operationalise the world’s first deep underground nuclear waste repository, offering a long-term solution for safe storage of highly radioactive spent fuel.

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• Finland has developed the Onkalo Repository on Olkiluoto Island, designed to safely store radioactive waste for up to one hundred thousand years.
• Since the nineteen fifties, global nuclear reactors have produced massive amounts of spent fuel, which remains hazardous for thousands of years despite no longer being usable for energy generation.
• The repository is built at a depth of about four hundred metres within extremely stable ancient rock formations, ensuring long-term geological safety and protection from environmental risks.
• The storage system uses multiple safety barriers, including sealed metal canisters, corrosion-resistant copper capsules, and protective clay layers to prevent radiation leakage.
• Bentonite clay plays a critical role by expanding when exposed to moisture, effectively blocking water movement and sealing potential pathways for radioactive contamination.
• The underground depth protects the waste from earthquakes, climate changes, human interference, and limits exposure to oxygen and groundwater, reducing corrosion risks significantly.
• The facility is designed for passive safety, meaning it will remain secure without maintenance or human intervention once the repository is permanently sealed.
• Finland’s approach provides a global model for safe nuclear waste management, strengthening confidence in nuclear energy as a reliable and low-carbon power source.